hypervelocity 22 lr research

[230RN]

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 [STRIKE]65,000[/STRIKE] 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]

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]

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]

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]

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/wikiped...px-Modern_bullet_vs_heeled_bullet_diagram.png

 

[fireman 9731]

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]

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]

See? This is why my wife refers to discussions like this as "gun porn".

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]

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]

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]

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]

67,500 RPM for the 1500 f/s cartridge, assuming 1:16 twist.

 

[tech30528]

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]

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....!

Terry, 230RN

 

[JohnBT]

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]

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]

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]

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....!

Terry, 230RN

Bookmarked it on the Kindle. Should be some good reading.

 

[C96]

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]

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]

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 [STRIKE]16 turns per inch[/STRIKE] one turn per 16" rifling twist will give you...."

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

Screwy, huh?

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

Terry, 230RN

 

[tryshoot]

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]

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]

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]

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.