223 Bullet weights for 1:7 twist

[TonyAngel]

ugaarguy, I don't know that I can agree with you on the quality of M193 ball. From what I understand it is only mean to be a 2 MOA performer. I know that I had, at one time, pulled a bunch of bullets from some LC stuff that I had. I got variances in bullet weight, length (when measured from the ogive) and variances in powder charges. I don't know that I'd call them big, but if my handloads were put together like that they would have wound up in the reject bin.

All of that aside, I've NEVER been able to shoot consecutive MOA groups with M193 out of any of my rifles. I say consecutive because luck does strike once in a while and it does happen, but not with any consistency.

If you get a chance, try pulling some bullets and do a comparison and see what you think.

 

[FlyinBryan]

All of that aside, I've NEVER been able to shoot consecutive MOA groups with M193 out of any of my rifles. I say consecutive because luck does strike once in a while and it does happen, but not with any consistency.

i will need to be somewhat educated on the definition of m193, but if it is the same bullet as the standard hornady 55g fmjbt bullet, open based, or having visible lead on the base, with a cannelure, then i have been able to very consistently shoot less than m.o.a. with them.

i would say at the very least, testing was (has always been) ten consecutive 5-shot groups averaging apprx. o.80",,, with more than one rifle (2) all fired from a bench, on bipods and squeeze bags. (fairly rapidly, or at least without consideration being given to heat, but fired, from a magazine, slowly enough to obtain trigger control as precisely as i can)

i should add that these are being loaded with 22grains of hodgdons extreme h322 in l.c. brass trimmed to 1.755, c.o.a.l. of 2.245, with an avg velocity of 3075-3125fps.

maybe what ive described is not remotely close to true m193. im interested to hear.

 

[ugaarguy]

Once I get all my reloading stuff setup I may sacrifice a few and do that. I'm not saying M193 is match stuff by any stretch. I'm simply saying that, based on what's supposed to be rejected according to the M193 Technical Bulletin that XM193 is very likely better constructed than the really cheap imported 5.56 / .223 FMJ. I need to weigh powder charges, and measure & weigh bullets on both XM193 and something like Tula or Wolf to get a comparison.

I've also not seen any real performance difference from M193 whether fired from 1:12, 1:9, or 1:7 twist bbls. Much of that probably has to do with using factory match ammo, or hand loaded match bullets when actually engaged in precision (attempted precision at least ) shooting.

I also had a Colt SP1 (1:12 twist bbl) that really liked Remington 62 gr OTM. Go figure.

ETA:

i should add that these are being loaded with 22grains of hodgdons extreme h322 in l.c. brass trimmed to 1.755, c.o.a.l. of 2.245, with an avg velocity of 3075-3125fps. maybe what ive described is not remotely close to true m193. im interested to hear.

What barrel length are you firing them from? Going back to that technical bulletin above:

INSTRUMENTAL VELOCITY: 3165 +/- 40 FPS (78 feet from muzzle) using a 5.56 test barrel, 20” long

XM193 is also supposed to be rejected if it doesn't meet this accuracy standard:

ACCURACY: 3-10round groups not to exceed 2.00” mean radius maximum average at 200 yards

 

[ugaarguy]

After reading back over the past few posts by myself, and a few others, all I can think is: We're a bunch of THR ammo / ballistics nerds.

 

[FlyinBryan]

well is the bullet i describe above the same as a m193 bullet? (i honestly do not know)

i should also add that these are not given any special care as far as trying to load them for accuracy. they just happen to be a pretty accurate load that i stumbled upon.

when i try to wring out some top accuracy, i carefully seperate cases by weight, casemouth thickness (for consistent bullet case tension), headspace meaurements from shoulder to the base of each case, seating .008-.010" off the lands, individual charge weight, etc, etc, etc,,,,,

these are really thrown together, coming off a progressive press at a pretty brisk rate (takes about 8 minutes to load 100rds) automatic case feeder, automatic shellplate rotation, really flying through them.

when i do everything i can, as mentioned above, and using premium bullets like 69gotm nosler custom competition, or hornady 68g hpbt, with hodgdons varget or benchmark, i can shrink that by an avg of 0.20 m.o.a.

 

[FlyinBryan]

After reading back over the past few posts by myself, and a few others, all I can think is: We're a bunch of THR ammo / ballistics nerds.

i would like to disagree with that statement,,,,,,,,,,,,,,,


but i cant do it truthfully

 

[ugaarguy]

well is the bullet i describe above the same as a m193 bullet? (i honestly do not know)

Forgot to address that, but yes. http://cmmginc.secure-mall.com/item/55-Grain-FMJ-M193-Projectiles-1728

 

[benzy2]

BTW, the twist needed to stabilize a bullet is NOT dictated by the bullet's weight, but its length. There are longer bullets out there that are lower in weight, but require the faster twist rates due to their length. A good point of comparison is the Sierra 77gr SMK and the Hornady 75gr A-Max. I've had 1:9 barrels that would shoot the SMK pretty well, but wouldn't shoot the A-Max at all. The A-Max is a long bullet and cannot be loaded to mag length. I've never been able to get the A-Max to shoot in anything slower than a 1:7.

This is what I have found as well. The 77gr SMK is fairly short for it's weight and is stabilized by a 1:9". Same thing for the 75gr Hornady BTHP. The 75gr Amax wouldn't stabilize but it is a longer design than the BTHP and SMK. 62gr Steel core M855 bullets aren't much shorter than 75gr BTHP or 77gr SMKs and I have a feeling the military built in a bit of a buffer on twist rate when they chose 1:9" for standard use with the M855.

 

[ugaarguy]

62gr Steel core M855 bullets aren't much shorter than 75gr BTHP or 77gr SMKs and I have a feeling the military built in a bit of a buffer on twist rate when they chose 1:9" for standard use with the M855.

I'm guessing you meant 1:7 (M16A2 & all subsequent 5.56 US Military firearms are 1:7). IIRC the 1:7 twist was chosen to ensure the really long 64 grain tracer would stabilize in arctic temps.

 

[benzy2]

For some reason I was thinking we went from 1:12 to 1:9 then 1:7. Either way, 62gr M855 is accepted to stabilize out of a 1:9". It's length is similar to some of the 73gr lead core rounds, and M855 isn't considered on the edge of what a 1:9" can handle.

 

[ziegler44]

I generally just stick with your standard 55gr. But I just went to this new gun shop and found a good price on some PMC X-Tac 62gr. Taking it to the range next week to see how it does. But yeah, you should be good with ≥55gr.

 

[Robert]

And they call this the high road. Assumptions. Insults.

No one insulted you directly. No one said Jeff56 is x,y, or z. They may disagree with what you say in a terse manner but no one attacked you.

But this stuff of calling what I said "BS" is over the line.

Just because they don't agree with you? My experience with 55gr bullets is vastly different than what you have described. My 1:7 barrel likes them just fine and I have never had one come apart on me. So which one of us is right? And if you disagree with me I will take it as a personal attack...

 

[helotaxi]

Jeff, what 55gn load in particular were you having issues with? Actual scientific analysis of light bullets with twist rates in excess of the minimum required to stabilize them reveals that there is no relationship between twist and accuracy so long as the twist is fast enough to stabilize the bullet in question.

Benchrest rifles are very specialized pieces of kit and essentially nothing from that discipline transitions to a practical rifle. Benchrest shooters build a rifle around a very narrow set of performance parameters and tune every part from the rifle to the load to their technique around the game that they are playing. At 100 yds, BC simply doesn't matter. As such, short, flat-based bullets are perfectly acceptable. Short bullets only require a slow twist and benchrest shooters go with the slowest twist that they can not because it makes any difference in how the bullet flies after it leaves the barrel but because the slow twist applies less torque to the rifle and upsets it less in the bags. That leads to repeatability. The difference is only on the order of tenths of an inch. Me personally, I'd rather have a rifle that can shoot a variety of bullets and loads in the 0.5-0.75" range than one that shoots one that shoots one load in the 0.1-0.2" range at 100yds only.

 

[P-32]

I might be comming to the party a little late but.....A 1 in 7 should shoot about any bullet you can load up to at least 80 gr. SMK's. I have some Berger 90 gr. bullets I have not tried yet.

I have a AR with a 1 to 6 1/2 twist, (dreamed of shooting 90 gr bullets out to 1k but the 80's will make it.) I have shot all SMK weights out of the 6 1/2 with no ill effect. I like the 52 gr SMK's for reduced matches. This set up has won me money and matches. I also have a 7 to 1 twist that has only seen 77 and 80 gr. SMK's.

For those who care both uppers were built by White Oak Precision.

I have seen bullets fragment on their way to the target but these were all 168 SMK's coming out of a 1in 10 twist rifle.

I have never seen any weight of GI ball shoot tight groups compaired to tailored reloads. I've shot a bit of both. Special Ball might be close in some cases but it's 30 cal.

 

[Robert]

It's also beyond the rules of this board.

If you feel that anyone has broken the rules of THR you best bet is to hit the report button and have the mods take a look at it.

I just don't like vulgar and arrogant comments directed at me.

It was directed at your assertation that 55gr bullets will fail in a 1:7 barrel. I am paraphrasing.

I take everything I read on the internet with a large grain of salt. 6mmbr is a great site and I have used information I have learned there. But it, like here, is a web site contributed to by people. Just because they, you, or anyone else says something does not mean I will take it to heart as gospel. I rely on my own experience first. And as I have said my experience is vastly different than yours and the source that you mention. Am I wrong since my experience differs with your venerable source? Or is there an allowance that in the firearms world we often find enough variable that there is no hard and fast answer? And that the shooter is best advised to try several different loads with different bullet weights to see what works best in their individual rifle.

The problem is, that all rifles will shoot a little bit different. My 1:7 AR mutt will shoot different than a bench rest rifle will shoot different than a JP CTR 02. Take 10 of the same rifle and they will all shoot slightly different. My rifle will shoot 55gr bullets all day long and make hits with ease. Boringly so. But that does not mean that every rifle will do the same. I do not shoot Bench Rest, if I am honest it bores me to tears. So I do not go to that level of expectation out of my rifle or my ammo. I can ring steel at 425y all day long with my AR using hand loads and .gov ammo and that is good enough for me.

 

[Bartholomew Roberts]

So when the people at 6mmbr said a 55 gr. bullet could spin apart in a fast twist rifle they were what, lying?

Well, they damn sure weren't talking about any rifle shooting .223 Remington SAAMI ammunition - or even 5.56 NATO ammunition. Short of specifically designing such a bullet, there is no way you will ever push a 55gr bullet out of a 1:7 barrel fast enough to spin it apart using .223 or 5.56 pressures.

Maybe in the benchrest world where someone necks down a .30-06 cartridge and loads a .223 round in it that might happen; but for 99.9% of the people discussing .223 in 1:7 twist this is a non-issue.

My own personal experience has been that my 1:9 and 1:7 twist barrels shoot 55gr ammo equally well; but then again I do very little shooting where increments of 0.1" are an important difference. I also have a military test somewhere they compared 55gr ammout out of a 1:12 barrel and a 1:7 barrel at 300yds. The group size was identical. You can find the actual document in past posts of mine on this subject if you feel like searching.

Again this serves to show that over spinning a bullet can cause accuracy problems according to science (despite what you said).

It doesn't cause practical accuracy problems for most people however.

 

[wingman]

Difficult to rely on stats to say that a given twist will shoot well, really just guide lines it's nothing more. I've fired a lot of 223 however most at 100 yards in 1/9 twist barrels both bolt and automatics all preferred the 52 gr match for consistent accuracy that includes my stag AR, none of my 223's are that consistent with 68, 69,74 gr bullets but again remember at 100yards. I've only found one bullet in 55gr(Berger match) that will come close to the 52gr.

Best to consider what distance you want to shoot before working up a new load, if I have the opportunity to shoot at 300 I will go back to the larger bullets.



I consider it all part of the hobby of shooting/reloading you just never know what you got until you crack open a new box of bullets and crank out new loads.

 

[benzy2]

So has anyone actually seen a 55gr bullet come apart from a .223rem or 5.56 nato chamber or is it all internet hype?

 

[FlyinBryan]

So has anyone actually seen a 55gr bullet come apart from a .223rem or 5.56 nato chamber or is it all internet hype?

ive never seen it, and to be honest ive never even heard of it. i seriously doubt its ever happened unless there was a major defect in the bullet.

So when the people at 6mmbr said a 55 gr. bullet could spin apart in a fast twist rifle they were what, lying?

i think the key word here is could

in my opinion, even shooting very light bullets at very fast speeds, 1/7 twists that have problems are going to be about as common as 1/9's having problems with 68-69's

rare air

 

[benzy2]

Again, Jeff, have you seen a single instance, in person or online, where a .223Rem or 5.56 has spun a 55gr apart? Theory aside, as I don't care to argue it from either side, certainly many people have shot 55gr rounds through a 1:7 twist so if there was a problem of 55gr bullets coming apart it should be easily found, right? I'm not interested in if people think the twist "can" pull apart a 55gr bullet, I'm interested in if people have seen it happen in real life. If so, clearly your views are correct. If not, maybe it isn't an issue, regardless of what a few people on another board think "could" happen. Bullets have been shot so theory should have been tested by now, right?

As for why not to put an ultra fast twist barrel on every rifle, I've heard it more to do with heat, friction, and wear than anything else. Seems the faster you spin the bullet, the faster you wear a barrel out.

 

[TonyAngel]

FlyinBryan, M193 is the military designation for a 55gr FMJ projectile loaded to their specs. I really don't know what it is supposed to apply to because the designation is used pretty loosely by many manufacturers, but it usually applies to military surplus or spec ammunition.

When I buy M193, I try to get the Lake City stuff and those projectiles are NOT the same as the Hornady 55gr FMJ projectiles. In fact, the Hornady stuff that you are referring to is usually what I use when loading bulk ammo because it does shoot a lot better than the mispec stuff.

 

[FlyinBryan]

In fact, the Hornady stuff that you are referring to is usually what I use when loading bulk ammo because it does shoot a lot better than the mispec stuff.

well, it does shoot very well for sure, and they are cheap too. ive been getting 500pcs at a local reloading supply for 38 dollars. its really hard to beat.

i also dont load them to any specs other than what i have found to be the best out of our barrels, which is most likely somewhat slower than whatever mil-spec calls for.

 

[AR-15 Rep]

OK... There are many factors to consider when choosing barrel twist rates.
1. Length of barrel
2. type of barrel steel ie 4140, 4150
3. chrome moly vs chrome lined
4. type of ammo .223 ( 55k chamber pressure ) 5.56mm ( 62k chamber pressure )
5. projectile weight
6. propellant used ( projectile velocity rates )
7. Flash hider, muzzle brake, target crown etc affect accuracy
8. Type of barrel Rifling ( button grooved, Polygonal, etc )
9. Barrel harmonics

In short, there are many factors to consider. These are just some off the top to think about.

 

[Bartholomew Roberts]

I've presented multiple sources about the possibility of lighter bullets spinning apart and all based on science.

Jeff, you said... and I quote:

but if you're buying off the shelf ammo those 55 gr. bullets are liable to rip themselves apart before they reach the target just as others have said.

Not one of the "sources" you've presented says anything about 55gr bullets from a .223 SAAMI chamber or 5.56x45 NATO chamber spinning apart - and for good reason - it doesn't happen.

You aren't going to spin any off-the-shelf 55gr bullet apart in a 1:7 barrel with a .223 chamber or 5.56 NATO chamber. It won't happen. This isn't a matter of opinion, it is a matter of cold hard fact.

 

[451 Detonics]

Even in a one in 10 twist I have to get a 55gr up to over 4200 fps to get one to blow up occasionally and them only a couple brands of bullets. With the 53 grain V-Max even over 4300 it has never happened...can't see it happening at .223 velocities unless the bullet is damaged.

I shoot a 1/7 twist in a Colt upper, it loves the BVAC 62 grain bulk ammo, doesn't do as well with 68 grain match...every barrel is different.