hypervelocity 22 lr research


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tech30528
March 18, 2012, 11:53 PM
Hello all, been catching your threads online in research for some time and decided to join.

Ok, so first some background. I'm a numbers guy. I love math. I'm a 42 year old L1 ASE Master auto tech and own an auto repair shop. I absolutely love the 22 lr platform and am mostly a target shooter. I have several 10 22s that are well built for specific purposes and a couple of 22 pistols as well.

I've tested over 20 different kinds of ammo with different rifles for varying distances. My personal favorite over thousands of rounds of testing is the CCI AR Tactical. For overall accuracy and dependability I find that these are the best. Granted all three of my test rifles are 10 22s, but they range from nearly stock to full custom.

My recent adventure is stretching what some consider the usable range of the 22lr. To give you an idea, we are shooting pingpong balls off golf tees at 350 feet with a 10 22 with a 17 inch Majestic barrel using 1200 fps ARTactical ammo. Granted, I weigh my ammo and separate it by .1 grain increments. I have a rim gauge but I've found rim variation to be nearly insignificant.

In order to stretch the range of these rounds I've gone to testing hypervelocity rounds. What I've found is that they just don't group well. But I know why. These hypervelocity rounds are smaller. The standard 1/16 twist barrel is over spinning them. Using the modified Greenhill Equation, I find that these shorter rounds require a slower twist rate.

Now, Green Mountain makes a 1/18 twist "Stinger barrel", but that barrel is heavy, and I like my rifles light. So after contacting several different barrel makers, I found one willing to make me a slower twist aluminum barrel. For the blanks he had available I couldn't, get a 1/18. What he could get was a 1/20, which is what is used for 22 shorts. Look at the grain weight of a 22 short vs a hypervelocity 22lr. Pretty close, huh?

So, I've done a lot of testing so far and still have some to do. Just wanted to know if anybody else might want to get in on this discussion. I'll tell you this: I just outfitted that custom rifle. With a 20MOA drop scope mount because I ran out of adjustment on my 24x scope at 150 yards and I'm still grouping pretty well with what I consider to be subpar ammo.

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firesky101
March 19, 2012, 12:41 AM
There is only so far you can go with velocity. At a certain point, heavy slow bullets have less drop due to the momentum overcoming the drag better. For accuracy generally heavy is the way to go. I am looking to get the 1:9 volquartsen barrel for stabilizing the Aguila 60gr SSS.

rcmodel
March 19, 2012, 12:46 AM
What I've found is that they just don't group well.Yep!

You should have ask.

Lots of .22 shooters here could have saved you the money & time testing them again.

rc

VA27
March 19, 2012, 12:50 AM
I've done the small bore/long range thing, only I went the other direction. Instead of hypervelocity, I use CB caps. I genned up some reduced paper silhouette targets. At one hundred yards they appear to be one thousand yards away. Computing drop is fun, and you better be able to read the wind. I've also shot the CB's on a handgun metallic silhouette range (rams at 200 meters!) and have gotten a few others to try it. It's great fun, but not for the easily discouraged!

JohnBT
March 19, 2012, 09:44 AM
The problem with hypervelocity rounds at longer distances is that they don't stay above the speed of sound all the way to the target. As the speed drops from above the speed of sound to below the speed of sound the turbulence knocks them off course. Think of it as a reverse sonic boom if you will. Ever see the film of the X-1 breaking the sound barrier? Shake, rattle and roll.

There's a reason rimfire target shooters use standard velocity ammo even at shorter distances. It's subsonic.

John

edited to add: Speaking of 1 in 19 twist, Gary Mitchell's famous record-setting Suhl .22, Old Blue, was already a record-setting rifle when he bought it from K.C. Young. Mr. Young owns a local range I belong to, so I guess I missed my chance. Although I didn't know it at the time, it's a 1 in 19" twist.

tech30528
March 19, 2012, 11:47 AM
Ah yes. The transonic bump. I'm well aware of that. Thing is, a lot of high velocity rounds deal with that, it's just a matter of where. For instance, the AR Tacticals (1200 FPS) I like so much are just barely supersonic. They break just a few meters out of the barrel. The transition is somewhat misunderstood as it is not really the sound wave "catching" bullet so much as it is the forward shift of the center of gravity that occurs during the transition. Truncated rounds handle this better, hence the 1 1/4 inch groups I'm seeing at 100 yards with these out of the 1:16 barrel. What I'd be interested in seeing is a truncated 30 grain.

I don't see the cost of this 1:20 barrel being a loss. It was less than $300, less than my standard ammo order. I shoot a LOT. I have 4 different ranges at my house. Plus it's the only aluminum fluted and threaded 1:20 twist barrel I know of. Thing is much of what we are told about rimfire is old information, and there is a lot of new stuff coming out. For instance, when the PMR 30 hit the market, it had cool factor just because it holds 30 rounds (as did it's predecessor, the Grendel 30), but since the 22 WMR has long been a rifle only round it didn't live up to it's potential in the pistols. Enter the Hornady V Shock WMR pistol round, loaded with a faster powder specifically for the benefit of shorter barrels. So don't accept everything you've heard.

These smaller faster rounds can be stabilized, it's just that nobody's really done it yet (we'll get in to that later, you might be surprised what these things can do with a slower twist rate). I'm not saying these rounds will rival the WMR, they can't. The case pressures would have to be way too high. But they can come awfully close, and do it much cheaper. This is hobby stuff. If we are going out hunting I'm sure we all have some bigger caliber stuff to do that with. But I'm having a pretty good time on the cheap playing with this, as I imagine some of you are too.

tech30528
March 19, 2012, 11:49 AM
Yep!

You should have ask.

Lots of .22 shooters here could have saved you the money & time testing them again.

rc
I'll get in to that. I've seen huge inconsistency in batches (no surprise there for any of the rimfire guys), along with some pretty surprising results. For instance, shooting from the same box out of 1:16 and 1:20 barrels side by side.

Tinker
March 19, 2012, 12:17 PM
(Disclaiimer: You guys are totally out of my league with this discussion on precision .22 shooting, so forgive a layman's imput...)


Those cartridges you say are just barely supersonic....could you use additional barrel length (in correct twist) to tame a supersonic round before it leaves the barrel?

230RN
March 19, 2012, 12:27 PM
???


The transition is somewhat misunderstood as it is not really the sound wave "catching" bullet so much as it is the forward shift of the center of gravity that occurs during the transition.

Don't you mean the forward shift of the center of pressure?

youngda9
March 19, 2012, 12:32 PM
Are you trying the high-dollar ammo? Like Lapua...that stuff is great.

tech30528
March 19, 2012, 01:26 PM
Ok, a few things here. I'll try to keep this stuff straight as I did a lot of these tests some time ago (but all within the last year).

First, additional barrel length will not stabilize the barely supersonic rounds because of additional control. I chrono tested several different rounds including the Aguila SuperMax with 16.5, 18 and 20 inch barrels and there was no significant speed difference. To be fair my focus was to see what I wanted the barrel length to be on that custom one, so I was focusing more on the fast stuff. However, I have a friend who shoots a CZ with a very long barrel and he claims tighter groups with barely supersonic stuff. I suspect what is happening there is that the bullet is reaching it's max speed in the barrel and after near complete powder burn it is slowing down, leaving the barrel subsonic.

Old Dog Man
March 19, 2012, 01:29 PM
I have a Rem. 581 22lr, 1/16 twist and have done a lot of testing with various brands of ammo. It doesn't like any of the hyper stuff, it really shoots good with Rem. round nose gold colored ammo. The cheap stuff, it will shoot Aquila ok and rem. target ok. doesn't like hollow points or truncated bullets. I mostly shoot long range PD with it, but am going to take it Fri. to a 600yrd. range and see what it will do on paper. I have put a second screw in the action in front of trigger guard, glassbedded it, recrowned the barrel, and flooated barrel. Have a 6x24 scope on it, longest PD kill Measured 367yrds. longest hit 450yrds. had to slide rifle fordward in bag to see hit on 450yrd. shot, but 367yrd it looked like a little dog setting in bottom of scope. Have wittness but they said they would not back me up because everyone would call them liars too. Now they all have shot them past 300yrds. Don't think I would like a 20moa base on a 22lr. Had one on 25/06 for really long range it worked good. Al

tech30528
March 19, 2012, 01:35 PM
Yes, I have shot the high dollar stuff. That was a separate test. All of what I shot was subsonic including Midas, Eley EPS, CCI Greentag, RWS and Wolf. Much to my surprise, accuracy was not in the order of cost. I shot about 100 rounds of each with different rifles but all in sets of 10 at a time. So it was two rifles with ten rounds each type per rifle on 5 different sets and in different orders to help eliminate residual lubrication factors. One rifle had the Majestic 17 inch aluminum barrel, the other a Ruger stainless barrel. The tightest groups overall were with the EPS at 34 cents a round, the second was the Midas at 32 cents a round with very little difference between the two. The shocker was the third best with an average group size difference of just 1/16 of an inch larger than the Midas at 100 yards, the CCI Greentag at 16 cents a round. The others weren't even really close.

tech30528
March 19, 2012, 01:39 PM
No. As the round slips subsonic it essentially has a braking effect. You know when you hit the brakes at high speed in your car and the back end comes up? The car essentially becomes front heavy because of the center of gravity shift, it's kind of like that.

JohnBT
March 19, 2012, 01:47 PM
"I suspect what is happening there is that the bullet is reaching it's max speed in the barrel and after near complete powder burn it is slowing down, leaving the barrel subsonic."

It's a fact, proven long ago.

There's an interesting article in the current issue of Precision Shooting on the necessity of shooting anywhere from 20- to 40-round groups to actually establish the true center of the groups. His conclusion was that the really tiny, neat little 5-shot groups we all love are not usually where the larger groups end up on the target. Some the author's groups, with some ammo, actually made two distinct groups within the larger 40-shot group.

Going from memory, he had an airtight building with a car-sized concrete base to mount the return to battery mount he had made. It weighed something like 75 pounds. After testing ammo on the 35 yard indoor range, he moved outside and retested in calm conditions at longer distances.

Anyway, I need to take the time to sit down and study on what he took years to document.


"The transition is somewhat misunderstood "

By whom? It's well known. I was surprised you didn't even mention it. It's probably the largest factor affecting accuracy when shooting hypervelocity ammo.

tech30528
March 19, 2012, 01:47 PM
I have a Rem. 581 22lr, 1/16 twist and have done a lot of testing with various brands of ammo. It doesn't like any of the hyper stuff, it really shoots good with Rem. round nose gold colored ammo. The cheap stuff, it will shoot Aquila ok and rem. target ok. doesn't like hollow points or truncated bullets. I mostly shoot long range PD with it, but am going to take it Fri. to a 600yrd. range and see what it will do on paper. I have put a second screw in the action in front of trigger guard, glassbedded it, recrowned the barrel, and flooated barrel. Have a 6x24 scope on it, longest PD kill Measured 367yrds. longest hit 450yrds. had to slide rifle fordward in bag to see hit on 450yrd. shot, but 367yrd it looked like a little dog setting in bottom of scope. Have wittness but they said they would not back me up because everyone would call them liars too. Now they all have shot them past 300yrds. Don't think I would like a 20moa base on a 22lr. Had one on 25/06 for really long range it worked good. Al
That's interesting. I haven't played with Remingtons, I'm still pretty new at this. Where I am finding a sight line that long is tough since we are in the mountains. I think I'd like that kind of shooting.

tech30528
March 19, 2012, 01:59 PM
"I suspect what is happening there is that the bullet is reaching it's max speed in the barrel and after near complete powder burn it is slowing down, leaving the barrel subsonic."

It's a fact, proven long ago.

There's an interesting article in the current issue of Precision Shooting on the necessity of shooting anywhere from 20- to 40-round groups to actually establish the true center of the groups. His conclusion was that the really tiny, neat little 5-shot groups we all love are not usually where the larger groups end up on the target. Some the author's groups, with some ammo, actually made two distinct groups within the larger 40-shot group.

Going from memory, he had an airtight building with a car-sized concrete base to mount the return to battery mount he had made. It weighed something like 75 pounds. After testing ammo on the 35 yard indoor range, he moved outside and retested in calm conditions at longer distances.

Anyway, I need to take the time to sit down and study on what he took years to document.


"The transition is somewhat misunderstood "

By whom? It's well known. I was surprised you didn't even mention it. It's probably the largest factor affecting accuracy when shooting hypervelocity ammo.

Well, the way other shooters have explained it to me was akin to a jet wash, and in reading I found that it wasn't so much an external force as internal. I've even had some tell me that the disruption is temporary and the bullet will restabilize. That seems a bit odd as it would be difficult to understand how the bullet would "find" it's original track. In other words, if this transition was solely to blame, it would seem that the longer distance from the transition to the target was the larger the spread would be. I would like to read the study you are referring to. I'm by no means an expert on this stuff, it's just that this particular area interests me a great deal and there is not as much information on it as I would like to see. So I end up doing a lot of reading and then doing a lot of shooting while trying to eliminate any repeatable variables, such as having the accuracy of the Greentags affected by left over lube from the previous rounds tested which are different. The RWS and Wolf stuff is oily as opposed to the waxy feel of the Eley and Midas stuff.

As luck would have it, it seems this was the right place to go to find people who can offer some insight.

JohnBT
March 19, 2012, 02:05 PM
"the center of gravity shift"

My (limited) understanding is that the Center of Pressure moves forward toward the Center of Gravity in the trans-sonic zone and the shift throws the bullet off.

The info at the link states that the Center of Pressure is "a function of the body's shape"

www.fas.org/man/dod-101/navy/docs/es310/ballstic/Ballstic.htm

I need to find Frank Terrell's work on this. He had movies iirc.

tech30528
March 19, 2012, 02:52 PM
Nice, thanks for that. I'll have to check it out later. The computer I'm on is a relic and doesn't handle video well. It's just back here in the shop for text and schematics and such.

If the weather holds out I'm planning on some test sets of the Stingers tonight. Shot a couple of strings of the Aguilas yesterday, solids and HPs and repeated my earlier results. I need to get some more Stingers for testing. I'm out of solids and prefer to keep the few segmented hollow points I have left for other purposes. But I've got a couple hundred of the hollow points left, enough for a consistent look at grouping I think. The 100 yard range I use for this has space for 8 targets shooting prone off of a shooter's bag.

230RN
March 19, 2012, 03:04 PM
My (limited) understanding is that the Center of Pressure moves forward toward the Center of Gravity in the trans-sonic zone and the shift throws the bullet off.

I asked about that already. The CG doesn't change in flight. The center of Pressure (CP) may, though, at different and changing velocities, especially in the transonic zone. This depends on bullet configuration.

Hey, let's remember that the bullet RPM changes with velocity, too. The lighter, hence faster, bullets will spin faster than heavier, slower bullets out of the same barrel with a given twist. Same is true with the same bullet out of shorter versus standard vs longer barrels.

The Greenhill formula is only a first approximation, and as far as I recall, velocity, per se, doesn't appear as a term, although the spin will change with that velocity with a given twist, so it's "sort of" taken care of in the formula.

However, since the faster, lighter, shorter bullets will spin faster, the formula kind of falls apart at the extreme ends of the bullet weight/density spectrum. I point out here also that density of the bullet is a significant factor, and most of the lighter bullets are hollow-pointed, effecively giving them an effective lower density.

However again, (ha-ha), since these effectively less dense bullets require a faster spin, their higher velocities will make them spin faster anyhow with a given twist.

The formula must also be factored according to the square root of the density of one projectile divided by the density of another projectile of the same proportions. Thus, an aluminum bullet will require SQRT(density of lead [10.9*] / density of aluminum [2.7]) more twist than a lead bullet that has the same profile and dimensions. Twice as much, in fact. (It also depends on the density of the medium through which the bullet travels, which for air in subsonic velocities, is 1.0.)

I prefer to call it the Greenhill Rule of Thumb rather than formula. He did a good job of trying to nail down all these variables in one mathematical package, but the result is just a starting point.

Truly it is said that every rifle is a law unto itself.

And also, every bullet is likewise a law unto itself.

The Greenhill Approximation eliminates a lot of preliminary testing, but it ain't like Ohm's Law or anything.

That's why it's so much fun to try different bullets and powders for centerfire loads, but for rimfires, about all you can do is try different brands, styles, etc in a given rifle and obtain conclusions for that particular rifle as to which ammunition is most accurate at which range.

Terry, 230RN

* 10.9 is for "average" jacketed bullets. For pure lead it's 11.34.

REF;

Hatcher's Notebook, p 556

tech30528
March 19, 2012, 04:06 PM
Niiice post. Man, that's some stuff to wrap your head around. I did some reverse figuring after testing match grade (subsonic) rounds with chrono testing and found that the "optimum" numbers based on that calculation did not add up, even when using other numbers to compensate for velocity. One thing I did was to use numbers from some extremely accurate combinations (sniper stuff) and use them to proof the equations. While they were reasonably close, even when applied to the 22lr the numbers were off enough to err on the side of slower twist rather than faster. So while the 1:20 I ended up with is actually a little slower than what the calculations came up with (somewhere around 18 1/2 IIRC) it seemed that using the equations available it was better to under spin than to over spin.

youngda9
March 19, 2012, 04:51 PM
What size 5-shot groups @50yds are you shooting with your rifles?

tech30528
March 19, 2012, 05:06 PM
It's been a long time since I've shot that close with a rifle. It varies by ammo and rifle of course, but the AR Tactical (1200 FPS 40 gr) with the 1:16 barrel is about 1 1/4 inches at 100 yards. I've kept some of the other targets and notes from some of the other tests, I'd have to look at those to be more specific. Got this one though from Thanksgiving weekend. Pretty indicative of this rifle and ammo combination. The X in the lower left was from my sister in law's set. She was shooting the target below this one. That was a fun day. 4 of us got to shoot that distance with the 22s before breaking out the Mosin and making a mess of a pumpkin.:D
http://i2.photobucket.com/albums/y22/tech30528/target.jpg

50 yards might be interesting for the fast stuff though since that is before the transonic break to see what it would do.

JohnBT
March 19, 2012, 05:39 PM
"I asked about that already. The CG doesn't change."

Hey, I'm lucky I remember anything. It's been 45 years since I left home to attend college - as a physics major :banghead:

230RN
March 20, 2012, 02:36 AM
Niiice grouping, there, tech30528 !

Not only an accurate rifle and shooter, but accurate sights.

Just for general reference, in your thinking about all this, the "usual" .22 round / rifle combination with about 16 turns per inch rifling twist will give you about 65,000 50,000 TO 54,000 RPM bullet spin. On the other hand, many varmint and high-power centerfires may get up to 250,000 RPM spin, figuring a rifling twist of about one turn in 7" to 9" and a velocity around 3,000 fps.

Just to give you a general idea as to how rifling twist and velocity and bullet RPM relate.

Terry, 230RN

tech30528
March 20, 2012, 12:42 PM
Thanks. I have until recently relied on scopes because of astigmatism. So if trying to use open sights I couldn't line up the front sight and see downrange. But I recently got contacts that changed my whole perspective. Guess the scope reliance is why I got in to stretching out the range in the first place. Recently discovered I SUCK with a pistol, so I picked up a Walther P22 with a laser and put together a range where I can practice stationary or moving with multiple targets. Much cheaper to learn this way as opposed to buying bigger cal ammo. I've got a Glock 33 that I dropped a 9mm barrel and springs in to to make practice cheaper, but the 22 allows me to really put some rounds down range and the laser helps with sight alignment. Then I'll go back to the Glock.

Been thru the Appleseed program (highly recommended for any level shooter), turned down the instructor hat, but still train a little on the side. I've got a 25M range at home too, and my instructor friends keep the AQT targets coming. I averaged 235 on that with a small scope, haven't gone back to it since I started with the pistol and the contacts. I'm looking in to bigger calibers eventually and reloading as well, which is why I'm so anal with the rimfire stuff. I'm getting my education cheap before I get in to the big boy stuff. I don't much care for the AR platform, but the interchangable uppers would be nice. I'm leaning toward the Mini 14 for a .223, but really want to play with .204 Ruger. What's not to like about 4000 FPS for a math guy?

230RN
March 20, 2012, 04:07 PM
That Ruger will spin the bullet at 240,000 RPM.

The 220 Swift used to be notorious for making bullets evaporate (fly apart) in reloads. In the factory load at 4100 feet per second muzzle velocity and a twist of one turn in 14 inches, it spun the bullet at 287,000 RPM, which was sorta OK. But of course handloaders used to try to beat the 4100 fps and would end up with a blue-ish cloud streaking toward the target.

Or, better, halfway toward the target.

I suspect but cannot document, that the smaller diameter of the .204 bullet will allow it to be spun faster without it flying apart. Centripetal and centrifugal forces and tensile strengths in a hot bullet versus diameter and all like that there.

I long ago found that my best accuracy was usually with loads a little bit below maximum in rifles.

.....

FWIW, and in case anyone's interested, here's how to calculate bullet RPM in a simple conceptual way:

Taking the simplest case, a muzzle velocity of 1000 feet per second and a twist of 1 turn in 1 foot, that is, a "12 inch twist barrel," the bullet will be spinning 1000 times in one second as it leaves the muzzle, that is, at 1000 Revolutions Per Second. Goes a foot, turns once, right? But it's going 1000 feet in one second, so that's 1000 turns in one second.

So in terms of revolutions per minute, that would be: 60 seconds in a minute X 1000 RPS(econd) = 60,000 RPM(inute)

But if the muzzle velocity is doubled to 2000 feet per second, this spin is doubled, thus:

(2000 / 1000) X 60,000 =

2 X 60,000 = 120,000 RPM

Similarly, if the twist rate on the rifle is "doubled", to, say one turn in 6", the RPM would be:

(12 / 6) X 60,000 RPM =

2 X 60,000 = 120,000 RPM

Now a 6" twist is pretty fast, so let's combine this all in a realistic example, a 3100 feet per second muzzle velocity and a rifle with a one turn in 9" twist. (This is approximately the "old" 7.62 NATO / .223 Remington loading and rifling.)

Taking the "standard" of 60,000 RPM in a 12" twist rifle with 1000 fps muzzle velocity, we can factor in both a different muzzle velocity and a different twist rate in our example as follows:

60,000 RPM X (3100 / 1000) X (12 / 9) =

60,000 X 3.1 X 1.333... = 247,999.9938 Revolutions Per Minute (RPM)

Meh. Call it a quarter-million RPM and let's let it go at that.

The method can be simplified mathematically in a neat formula, but looking at it this way gives a conceptual understanding of the formula.

Terry, 230RN

brickeyee
March 20, 2012, 04:58 PM
The .22 RF benchrest guys found that even target velocity .22RF bullets 'slump' and distort when fired, putting a real limit on accuracy.

The high velocity ones are probably worse.

230RN
March 20, 2012, 05:29 PM
A lot of that is due to the fact that .22LRs are "heeled," and the rear end is designed to expand on firing --like a Minie Ball or the pellet from an air rifle, where pressure opens up the base to fill the rifling. Hopefully, this expansion is uniform from shot to shot, bullet to bullet. So if you're expanding that part of the bullet's diameter, it necessarily shortens the bullet's length.

However, this points up still one more variable in the pursuit of "What .22 bullet or bullet weight or bullet composition or bullet "plating" or bullet nose configuration or bullet velocity or rifling twist or internal pressure curve or phase of the moon or state of the tides or how you combed your hair, is best?"

You will note that the .22 Magnum rimfires do not have heeled bullets --they are essentially the same diameter from end-of-ogive to base.

Terry, 230RN

REF (heeled bullet on right, not-heeled bullet on left):

http://upload.wikimedia.org/wikipedia/en/thumb/7/7c/Modern_bullet_vs_heeled_bullet_diagram.png/200px-Modern_bullet_vs_heeled_bullet_diagram.png

fireman 9731
March 20, 2012, 06:05 PM
Hmmm, very interesting. I have a Norinco mini-mauser 22lr Training rifle that I have been trying to do some accuracy testing with. I have no idea what the twist rate is, but it will shoot 29 grain CCI 22 short target ammo(830 fps) just as well as the CCI Standard velocity 40 grain ammo at 1070 fps. All of this is at about 75 yards. It doesn't like any of the super-sonic stuff at all. I haven't tried the AR Tactical yet though. So am I lucky and my rifle just has two sweet spots or am I crazy?

pseudonymity
March 20, 2012, 06:56 PM
I am interested in what you find out - I would think that the spin drift is not necessarily a major factor in the hypervelocity ammo grouping with less precision. After all, the twist rate is fixed, and while the spin drift may effect the trajectory, it should be constant and should not really effect group size when all other variables are much the same.

Most hypervelocity bullets are truncated cone, correct? If so, I would guess that the normally poor drag coefficient of the round nose bullet is made even worse with the truncated cone. Also, I would not expect precision in the cone placement with those rounds, which would lead to a bullet that was not balanced around the center of the cone even when at rest. When it is fired, the uneven drag created by the off center cone as well as the instability of the unbalanced bullet rotating probably have that bullet really wobbling compared to a better shape.

tech30528
March 20, 2012, 07:59 PM
See? This is why my wife refers to discussions like this as "gun porn". :D

First, I did not know that there was a difference in 22lr and 22mag bullet shape. But that explains quite a lot. I had done some testing with the high speed Aguila stuff and was very pleased with the performance, so I ordered a buttload more of it. Like 5000 rounds.

Went out to shoot and it looked like a shotgun on paper. I looked skepticly at my rifle. I checked the scope mount. I took it apart and cleaned it. I shot another equally disappointing set. So I went and grabbed a box of the old stuff, and there were my <2MOA groups. Bad batch I suppose, an interesting variable that doesn't apply to a lot of other calibers I suppose. Luckily my Walther P22 likes hot loads and this wasn't an issue. It didn't make that big a difference at pistol range.

A friend of mine has recently offered me a Ruger 77/22 in 22mag at a pretty decent price, but I have hesitated because I didn't want to just go one more step in rimfire for my next toy. Thought I might just make the jump to centerfire. But this opens up some possibilities....

tech30528
March 20, 2012, 08:13 PM
Ok, truncated HV rounds.

The short answer is no. Aquila (sorry to keep bringing them up, but they are the fastest things out there and I've tested them extensively) is not truncated. I'm currently testing the three Stinger variants I'm aware of, the common hollow point, the segmented hollow point (an absolutely devastating varmint round) and the newer solid. None of these are truncated. I really REALLY want to test some truncated HV rounds if anybody knows or any, because my favorite multipurpose ammo (again after waaay to much testing and measurement to the point of obsession.. maybe) is a barely supersonic truncated round. But if someone knows of a truncated HV round that is available for a decent price let me know and I'll run them thru my testing and see how they do.

Those AR Tacticals, BTW (which I now have most of my Appleseed buddies hooked on) are a great deal thru Cabelas. You get 1500 rounds in a PLASTIC dry box (I know, the military metal ones are far cooler, but I find many uses for these boxes, and they are bigger than a 900 round .223 box) goes less than $100. Thing is, if you watch the sales you typically see free shipping on orders over $100, and one box falls short. So I pair up with my buddies and place bulk orders so we can split the shipping savings. We each end up with 1500 rounds and a box that will hold 3 5 pound bags of flour for $95. Not bad for really consistent ammo. I don't know what everybody else uses the boxes for, but I have a breadmaker at home and a big smoker at the shop so I buy supplies for them on sale when I can and these boxes are awfully handy.

230RN
March 20, 2012, 10:38 PM
fireman 9731 observed:

Hmmm, very interesting. I have a Norinco mini-mauser 22lr Training rifle that I have been trying to do some accuracy testing with. I have no idea what the twist rate is, but it will shoot 29 grain CCI 22 short target ammo(830 fps) just as well as the CCI Standard velocity 40 grain ammo at 1070 fps. All of this is at about 75 yards. It doesn't like any of the super-sonic stuff at all. I haven't tried the AR Tactical yet though. So am I lucky and my rifle just has two sweet spots or am I crazy?

No.

Look at it this way, in terms of the bullet RPM for the different weights of bullets (and hence their different velocities):

29 gr @ 830 ft/sec 16" twist

(830 / 1000) X (12 / 16) X 60,000 = 37350 RPM

40 gr @ 1070 ft/sec 16" twist

(1070 / 1000) X (12 / 16) X 60,000 = 48150 RPM

But assuming a supersonic velocity of, say, 1350 f/s with a lighter bullet:

(1350 / 1000) X (12 / 16) X 60,000 = 60,750 RPM

Note that the ultra-high-velocity bullet is being spun about 25% faster than the 40-grain bullet, which is "comfortable" at between 49,000 RPM and 54,000 rpm. That's not the rifle's sweet spot, that's the bullets' "sweet range."

And you may be referring to even higher-velocity bullets in the 29- grain range, which somebody mentioned, which will have an even higher velocity (and hence RPM) than my assumed velocity of 1350 f/s above. My opinion is that your hypervelocity bullets are being overspun in your rifle with my assumed 1 in 16" twist. (See below.)

I point out that over many many decades (like about ten of them) the best rifling twist for .22 cartridges has been 1 in 16", which has been confirmed empirically for the normal range of .22 cartridges (.22 Short, .22 Long, and .22 Long RIfle). It is in almost universal use, even though it's kind of a compromise for those three cartridges and bullet weights and normal .22 velocities.

Ah, but comes now the craze for even higher velocity, and someone decided that they could advertise even more velocity, whoop-de-doo, and we'll sell a billion of them.

Except that with the "standard" twist of 1:16, accuracy falls off at the higher resulting RPM of the higher velocity lighter-weight bullets.

Hey, velocity isn't everything, folks.

Terry, 230RN

P.S. You may determine your rifle's twist by running a tight patch down the bore with a mark on the upper part of the rod so you can tell when it's made one rotation as it passes through. Place another mark right at the muzzle. Push the rod down until it has made one rotation. Mark the rod again and withdraw it. Measure the distance between the two marks you made at the muzzle, and that's your twist.

tech30528
March 21, 2012, 03:36 PM
Found truncated hypervelocity rounds. There are two, both by Remington. There is a 33 grain hollow point (Yellow Jacket) listed at 1500 FPS and a 36 grain solid (Viper) listed at 1410.

230RN
March 21, 2012, 03:40 PM
67,500 RPM for the 1500 f/s cartridge, assuming 1:16 twist.

tech30528
March 21, 2012, 04:28 PM
Aguila makes a round called the Interceptor that is on my next order list for testing anyway. It is a 40 grain solid round listed at 1470 FPS. I'm interested in this one for a couple of reasons. First, it is the same weight as the ones that group really well out of my 1:16 rifle. But now that we've been talking twist RPM as opposed to twist rate, it will be interesting to see what it does out of the 1:20 barrel. The twist RPM or the AR Tactical out of the 1:16 barrel would be almost exactly the same as the twist RPM of the Interceptor out of the 1:20 barrel with the same weight bullet. Can't wait to look at those groups side by side. Because if they are close, we may be looking at twist RPM as a stability marker instead of twist rate, which means finding a distance stretching round that groups well could be a matter of just picking a ratio of grain to speed for each twist rate.

230RN
March 21, 2012, 05:02 PM
First, it is the same weight as the ones that group really well out of my 1:16 rifle. But now that we've been talking twist RPM as opposed to twist rate, it will be interesting to see what it does out of the 1:20 barrel. The twist RPM or the AR Tactical out of the 1:16 barrel would be almost exactly the same as the twist RPM of the Interceptor out of the 1:20 barrel with the same weight bullet. Can't wait to look at those groups side by side. Because if they are close, we may be looking at twist RPM as a stability marker instead of twist rate, which means finding a distance stretching round that groups well could be a matter of just picking a ratio of grain to speed for each twist rate.

You have a .22LR rifle with a 1:20 twist rate? What brand, model, etc?

Re bolding in quote: That's what i"ve been saying. It's RPM versus length of bullet (i.e., "weight," among other profile parameters -boattail, hollowpoint, materials, etc.) which is important.

If you're math oriented as you say, you might find this interesting:

http://www.nennstiel-ruprecht.de/bullfly/

I've long had a problem understanding the concept of bullet "over"-stabilization. Intuitively, it seems that "if a little spin/twist is good, a lotta spin/twist must be better," but that's contrary to long-term practical experience and advice. (I am given to understand that some Bench Rest shooters will even change barrels to different twists for summer versus winter shooting.)

This thread got me interested in that again, but I haven't reviewed the above-cited article in depth yet... don't have time right now.

Maybe if you look it over, you can explain it to me....! :D

Terry, 230RN

JohnBT
March 21, 2012, 06:03 PM
Think about a perfectly thrown football pass, a long one. The spinning ball is pointed up as it rises and then noses over so the nose leads on the way down.

Then think about one that gets to the top but doesn't nose over; the front end stays up and it comes down side first and spinning just fine, but it sails because the fat side of the ball is leading the way. Sort of like a stalled plane.

Hmmm, off to google. Here...

"An overstabilized bullet flies with its point elevated or the way it left the bore. While an adequately stabilized one will fly with it's point following the trajectory curve. "

- www.angelfire.com/ma/ZERMEL/twist2.html

230RN
March 21, 2012, 07:10 PM
Unless I missed it, that article does not seem to address the velocity / twist / spin problem, and as I mentioned, the Greenhill "Formula" is only an approximation and also does not have a term in it for velocity. I would assume, therefore, that Greenhill was only addressing twist or spin in more or less "standard" velocity loadings available to him.

It's kind of frustrating that nobody seems to address the velocity /spin / rifling twist problem. Everyone seems to assume a velocity and let it go at that. Yet, here we have OP's problem-statement with modern-day hypervelocity cartridges in .22 rimfire which have come out only recently, relatively speaking.

Here's an interesting blog about it. Some good back-and-forth on the problem:

http://yarchive.net/gun/ammo/bullet_helical_path.html

It's apparent from my cursory scan of the material available on "over"-stabilization, that it does indeed has negative effects on accuracy due to wobble of the bullet noses (due to nutation and precession) changing with its velocity through its trajectory.

Hatcher (Hatcher's Notebook) has an interesting photograph of two shots through oak at close versus distant ranges (50 feet versus 200 yards), and it is clear that the bullets penetrated more, and in a nice straight line, at the longer ranges than at the shorter ranges. (See Pp. 405-408 op cit.) He says, in the caption to the long-range penetration photograph, "The range was long enough so that the bullet was sufficiently stabilized to continue point first and thus give good penetration." However, he does not go into details on this "sufficiently stabilized" remark.

I'm sure they did a lot of testing on this "thing" called "overstabilization" at the Aberdeen Proving Grounds, and I'm sure they have thoroughly nailed it down, but I haven't seen anything in that respect. Yet.

As Yul Brynner said in The King and I, " 'Tis a puzzlement."

<retires to man-cave to noodle some of this out in seclusion>

Terry, 230RN

tech30528
March 21, 2012, 08:30 PM
The 1:20 twist is a custom build. It's 16 1/2 inches, fluted and threaded aluminum and is on a 10 22 that is currently wearing a Dragunov style stock and a BSA 6x24 scope. The builder used an insert that has the "correct" twist for 22 short, which is about a 29 grain bullet. The Aguila SuperMax rounds I had it built for are 30 grain listed at 1750 FPS that were scattering like buckshot with a 1:16 and keyholing at 100 yards.

tech30528
March 21, 2012, 08:49 PM
You have a .22LR rifle with a 1:20 twist rate? What brand, model, etc?

Re bolding in quote: That's what i"ve been saying. It's RPM versus length of bullet (i.e., "weight," among other profile parameters -boattail, hollowpoint, materials, etc.) which is important.

If you're math oriented as you say, you might find this interesting:

http://www.nennstiel-ruprecht.de/bullfly/

I've long had a problem understanding the concept of bullet "over"-stabilization. Intuitively, it seems that "if a little spin/twist is good, a lotta spin/twist must be better," but that's contrary to long-term practical experience and advice. (I am given to understand that some Bench Rest shooters will even change barrels to different twists for summer versus winter shooting.)

This thread got me interested in that again, but I haven't reviewed the above-cited article in depth yet... don't have time right now.

Maybe if you look it over, you can explain it to me....! :D

Terry, 230RN
Bookmarked it on the Kindle. Should be some good reading.

C96
March 22, 2012, 01:13 AM
Terry back in post #25 you mention "with about 16 turns per inch rifling twist". I think you mean 16 inches per turn. I have never seen any firearm with 16 turns per inch. I did not check out your math to see if this was a consistent error or just a typo.

Allan

brickeyee
March 22, 2012, 01:09 PM
If the bullet is perfect there is no effect from spinning it faster than required for stability.

The problem is that bullets are rarely perfect, and spinning them faster than need exaggerates any defects in symmetry about ht rotational axis.

230RN
March 26, 2012, 01:33 AM
Thanks for pointing that out, brickeyee.


C96 corrected me:

Terry back in post #25 you mention "with about 16 turns per inch rifling twist". I think you mean 16 inches per turn. I have never seen any firearm with 16 turns per inch. I did not check out your math to see if this was a consistent error or just a typo.

Allan


C96, thanks for pointing out that error. It's past the editing window time, so I can't correct it. Should read as follows:

"Just for general reference, in your thinking about all this, the "usual" .22 round / rifle combination with about 16 turns per inch one turn per 16" rifling twist will give you...."

Yeah, that's like a 3/8-16 national coarse threaded bolt! :o

Screwy, huh?

I ain't perfect, despite what my mother used to tell everyone.

Terry, 230RN

tryshoot
March 26, 2012, 02:27 AM
6 22lr's I own or have shot better with standard vel. Diffrent rifles shot better groups with hyper. One remington 581 my neighbor had really made me mad. He bought another 1 for his son and I could outshoot it by far. We used to let others shoot our gun to see if gun or shooter. Firesky101 you are right. Aguila 60gr. sss will not shoot out of any 22 rifle I've got, BUTT my 22 conversion for my Bushmaster W/ 1 in 9 in twist is the only thing that groups at all! (I did mean ar-15 with drop in .22lr conv)

firesky101
March 26, 2012, 03:10 AM
I must clarify, since I have posted an great range day with my 10/22 on another thread. My houge target barrel stabilizes the 60gr pills "most" of the time. Every once in a while I get an odd flyer, so I am saving up for that voquartsen barrel. Plus it is shiny, so I can convince the wife.

tryshoot
March 26, 2012, 03:30 AM
60 gr was develapt for 10-22 custom barrel. Just works wonderfull in conv kit devel. 30 years before. When army devel. m16 had 1:12 twist for 55gr bullits. Had to up twist to 1:10 and then 1:9 for 62 gr. bullits. Happend to make m-261 22lr kit work wonderfull. Developed kit to make training cheaper, save ammo money.

tech30528
March 26, 2012, 11:02 AM
Ordered a brick of the Aguila Interceptors. 40 grain, 1470 FPS. Order should be in on Wednesday, I'll try to get a few hundred downrange this weekend and see what it does.

tech30528
March 31, 2012, 07:11 PM
Ok so the order finally arrived. Got 500 rounds. I'm in the process of weighing them now. This is something I do with with all the ammo I test (except for the match grade stuff because of price I didn't buy enough of each for statistical measurement) I'm about half done with the brick and it is looking pretty good. The median is 51.7 grains (total weight of case, primer, bullet and powder) . Here is the theory here. These rounds are Eley primed, so we are going to assume the primer loads and brass are consistent. If the bullets are consistent than the weigh difference from one to another would be powder which would translate to speed differences. It's as close an estimation as I can make and still fire the bullets.

So far the spread on these rounds is from 51.3 grains to 52.1 grains (and so far only one of those) . The vast majority are running from 51.6 grains to 51.8 grains which is fairly typical. For my favorive AR Tacticals the median is 51.3 grains with most of them running 51.2 to 51.5 grains. For shooting purposes what I normally do is shoot the more common weights as they are separated and use the less common weights on either end as pistol rounds.

I'll finish weighing these out tonight and weather permitting get some downrange tomorrow after church.

Orion8472
April 1, 2012, 10:49 AM
Coming into this discussion, late, and slightly out of my league. :o

I'm a novice .2lr shooter, so bear that in mind. I have a 10/22 with a Clerke 16" bull barrel with the Bentz chamber. It will not accept Stinger length casing rounds. I went with what I considered to be "the next best thing" when looking for a faster round. I use CCI Velositors and have gotten fairly impressive groupings with them at 100 yards. ~ 1 1/2 inches roughly. I haven't been out with it in a while and am having a bit of custom work done and plan on retesting it after the work is done. Just my 2 cents.

230RN
April 1, 2012, 11:22 AM
Hm. One index of the value of a thread is how many times I have to look up something someone mentioned because I didn't know it before. Never heard of a Benze chamber, so I looked it up:

http://www.riflebarrels.com/products/chamber_info.htm

From that site,


1.The drop-in barrels we manufacture for the Ruger 10/22 are chambered with a "Bentz" semi-auto match reamer and it is not as short as the other match reamers we use. Unfired ammo can be extracted from this chamber. We do not recommend using CCI Velocitor or Stinger ammo in the 10/22 barrel. Also see this FAQ on the subject - Click Here. (URL of that "Click Here" is http://www.riflebarrels.com/faq_lilja_rifle_barrels.htm#stinger



So from that link to their FAQ section, I find:



Q. Why do you recommend not using Stinger and Velocitor ammo in 10/22 barrels?

A. We chamber our 10/22 drop-in barrels with a Bentz semi-auto match type reamer. This type chamber is shorter and tighter than a standard sporting type chamber. As a result higher pressures are developed when the longer Stinger and Velocitor type ammo is fired in a shorter match type chamber. The end result can be a blown extractor slot in a 10/22 barrel with a match chamber. The following is from CCI:

"Where the problem resides is that the Stinger case is 0.100" longer than
a Long Rifle case, their chamber is not made to ANSI Sporting Chamber
dimensions, it's shorter, the Stinger case is then engraved by the
rifling and increases pressure. See the Warning on the back of the
Stinger packaging, ensure you know which chamber your rifle has. If not
an ANSI Sporting Chamber, do not use Stinger."



(I note the variations in speling of "Benze" and assume they all mean the same thing.)

So I am confused, Orion8472. Why are you using Velocitor ammunition?

Terry, 230RN

Orion8472
April 1, 2012, 12:53 PM
I spelled it wrong, but fixed it in my post. After your post I did another look into what I have [was told by someone else it was a Bentz chamber]. My barrel isn't a Lilja and I may have mispoke on it having the Bentz chamber, but just don't know at this point. Any information on Clerke barrels doesn't mention "Bentz". It definitely doesn't take the Stinger casing.

The Velocitor has a standard length casing, so am not sure why it would be included on that Lilja information page. I've had no issues when using Velocitors.

If true, I was comletely unaware of that information and will look into it further with my [excellent] gunsmith. But again, I don't see how the Velocitor can have the issues that the Stingers have with the Velocitor's standard length casing.

tech30528
April 1, 2012, 04:08 PM
Got a few rounds downrange today and ended up with a loose scope mount. Dammit. So today's results are inconclusive. Not even going to try to fix that here, I'll take it in to the shop this week and take care of it. Very strange. I have the same mounts on both rifles I was using today. Never had a problem with one, the other has given me problems on several occasions. Same rifles, same rails, same rings, same bottle of Loctite.:banghead:

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