223 Bullet weights for 1:7 twist

[dalepres]

I have a new, unfired so far, AR-15, home built. It has an 18-in 1:7 twist barrel. I know it can handle heavier weight bullets but what is the best, safest, and reliable weights for the lower weight bullets? Should I expect it to shoot 52 to 55 grain ammunition reliably?

Thanks,

Dale

 

[FlyinBryan]

you should have no problems with any bullets from around 50 grains and up.

i think a pretty good rule of thumb is 1/7 for bullets of 50 grains and up, and for 1/9 70 grains or less.

 

[midtennpawnstar]

I have a Bravo company/spikes tactical ar i put together and i went with the 1:7 primarily because i have a ton of 62gr pmc lap, from what i know thats the primary grain in mind with the 1:7 but like FlyinBryan says 50 grains and up your good....dont really want to go lower because your varmint loads like 45gr and lower could tear up with a tight twist.......happy shooting!

 

[Tape]

1:7 Twist 62-77 grain range

 

[ugaarguy]

1:7 twist will shoot any .223 / 5.56 bullet up to 77 grains. You can't over stabilize a bullet. If you decide to shoot very thinly jacketed bullets (typically marketed as varmint bullets) weighing less than 55 grains in a 1:7 twist bbl. keep velocity under 2800 fps to prevent tearing the jacket.

http://www.ar15.com/content/manuals/FM23-9.pdf p.210
Figure F-15B shows two 25.4-cm shot groups fired by the same skilled marksman at a distance of 274.2 meters, using an M16A2 rifle. The shot group on the left was fired (and zeroed) with M855 ammunition. The shot group
on the right was fired after substituting M193 ammunition.

M855 is 62 grain FMJ with a steel penetrater core. M193 is standard 55 grain FMJ. The M16A2 has a 1:7 twist barrel.

 

[Tape]

weighing less than 55 grains in a 1:7 twist bbl. keep velocity under 2800 fps to prevent tearing the jacket.

#of fps; glad you brought that up because many I have told say I'm full of it, that is the reason I didn't mention it, don't feel like bickering. I tell people that if spun to fast it can fall apart before it gets to the target.

 

[Red State]

What uagaarguy said.

55gr will be fine all day long, but 62gr will probably be better.

 

[ugaarguy]

#of fps; glad you brought that up because many I have told say I'm full of it, that is the reason I didn't mention it, don't feel like bickering. I tell people that if spun to fast it can fall apart before it gets to the target.

Yep, it's right there in the Speer Reloading Manual (and probably others). I'm sure they just made it up .

 

[helotaxi]

It depends on the particular bullet. The Speer TNT and Hornady SPSX are particularly fragile and run the risk of gyroscopic failure. The Sierra Blitzkings and Hornady V-Max can have the crap driven out of them without issue. I've also loaded some screaming Varmint Grenades (36gn) from my 1:7 and they held together fine and were fairly accurate.

 

[mshootnit]

Are there any weight 22 cal projectiles that 1/8 won't stabilize?

 

[supercalvin56]

I have a 7 twist 223 that shoots anything....even the 40 grainers. Try it, I'll bet you never have a problem, I haven't

 

[FlyinBryan]

weighing less than 55 grains in a 1:7 twist bbl. keep velocity under 2800 fps to prevent tearing the jacket.

i used to doubt people that said this until i lost a support rod and a sunshield on my chronograph because one poofed right between the chrony eyes.

it was last thanksgiving and we were shooting 45g bullets out of a 1/7. i was loading them @3500+ with varget.

i thought my chrony shorted out because it looked like sparks shooting out of it.
(shooting chrony has great customer service because i called them much later, like 6 months, and told them what happened, the truth, and they sent me new stuff for free.)

 

[rori]

Why have a 7 barrel if you don't want to shoot heavy bullets. My minis are 9's and I wish one of them was a 7 so I could run heavier bullets than the 65's I run now. Frank

 

[Robert]

I shoot 55gr bullets, both factory and hand loads of unknown velocity, in my 1:7 rifle with 0 problems. I have never had a 55gr bullet come apart before reaching the target. Ever.

55gr though 77gr should be fine in any reliable AR. I have a bunch of 62gr waiting to be loaded up. But I shoot at ranges up to 600m and like the heavier bullet.

 

[TonyAngel]

In answer to your question regarding 52 and 55gr projectiles, you won't have any problems with those. Actually, I'll say that you shouldn't have any problems with those. I really like the 52gr projectiles from Sierra and the 55s from Hornady and have had good results with them for ranges out to around 300 yards or so.

 

[UKWildcats]

Here is some good information on maximum bullet weights versus barrel twist -- http://www.6mmbr.com/223rem.html

Just be carefule shooting light bullets fast -- the jackets can be too thin to handle the spin rate and will fall apart in flight.

UK

 

[wingman]

I've owned 4 or 5 223's they all preferred 52gr match @100 yards. Honestly while it may be a 1/7 or 1/9 twist never know what it will shoot best until trying, but the 52 Berger match or 52 sierra has always been the most accurate for me.

 

[helotaxi]

I've heard it from so called experts that a 55 gr. bullet won't work well in a fast twist rifle. Even in a 1:9 twist barrel 55 gr. is too light. I know it isn't accurate at all in my 1:9 compared to heavier rounds. Bullets will spin themselves out of round which means accuracy goes out the window and the jackets can even rip right off the bullets. Yes you can overcome the problems if you load your own ammo and keep the speed down 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. They mentioned keeping the speed down but they didn't say what it takes to keep the speed down. It requires you loading your own ammo AFAIK. Maybe some off the shelf ammo is rated at those speeds but I don't know of any.

You can file all that in the BS department. Accuracy is a factor of barrel quality and matching a load to barrel harmonics. Unless you've tried to tune a load with a quality bullet to your rifle, you can't say that 55gn bullets won't shoot from your rifle. All you can say is that the loads you tried were not accurate. If you're talking about mil-type 55gn loads, the bullet itself was the cause of the poor accuracy, not the weight but the consistency (or lack thereof). I've shot from 36gn to 75gn bullets from my ARs (with both 1:9 and 1:7 twist) with acceptable accuracy and no bullet failures with modern style varmint bullets (not Speer TNT or Hornady SPSX). I've never made an effort to keep the velocity down either.

 

[dc.fireman]

Dalepres - I shoot Hornady 68 gr. BTHP's, and Sierra 69 gr. HPBT's, loaded over Varget powder. I'm currently working on a load for Nosler 77 gr. BTHP's. You'll be fine in the twist rate department for the heavier weight bullets. I think where you may run into a problem, is if you attempt to go with something which requires a longer-than-magazine length load (which for an AR-15, is slightly over the 2.260" mark). I forget if it's the A-Max, or V-Max - but one of the Hornady 75 gr. bullets may cause you problems if you decide to load it for the AR. The long bullet ogive, doesn't go well with the magazine length requirement. You can load them, and shoot them in single - fire fashion, just not from the magazine (easily, at least).

 

[Hocka Louis]

Flyin Bryan has it backwards. Tape is right.

1:7 is NATO for heavy heads about 62 up to and including 77 gr. tracer rounds. Those who have them get defensive about it and claim they'll do everything. OK Sure. Colt pushed them on the civilian market. If you have 1:7 forget buying less 62 gr. bullet ammo -- it isn't for you.

Someone mentioned a BSM -- my stainless target carbine is 1:8. They know better shooters are going heavy but never 77 gr. heavy! I could also make do with 55 in a pinch.

1:9 is kinda univesal 55 - 62.

Wanna shoot 55, and/or 55 or less!? 1:9 or SLOWER twist if you can. The original was 1:14, then 1:12. 1:11 you'll sometimes see for 55 and lighter as well. Even 1:10.

 

[ugaarguy]

1:7 is NATO for heavy heads about 62 up to and including 77 gr. tracer rounds. Those who have them get defensive about it and claim they'll do everything. OK Sure. Colt pushed them on the civilian market. If you have 1:7 forget buying less 62 gr. bullet ammo -- it isn't for you.

I guess US Army FM 23-9 is lying. The M16A2 (1:7) shoots M193 (55 grain) as well it shoots M855 (long 62 gr steel core), and as well as the M16A1 (1:12) shoots M193.

Someone mentioned a BSM -- my stainless target carbine is 1:8. They know better shooters are going heavy but never 77 gr. heavy! I could also make do with 55 in a pinch.

Never 77 gr? That's a bold statement. Black Hills sold so much Mk 262 Mod 1 (77 gr SMK w/ cannelure) overrun ammo that they started offering it as a standard item being sold 5.56 77 gr OTM.

1:9 is kinda univesal 55 - 62.

Or you could say 1:9 is too fast for really thinly jacketed light bullets, and too slow for the really long (aka heavy) stuff. (Unless you have an exceptional 1:9 twist bbl. like one member here which will stabilize the 77gr stuff).

Wanna shoot 55, and/or 55 or less!? 1:9 or SLOWER twist if you can. The original was 1:14, then 1:12. 1:11 you'll sometimes see for 55 and lighter as well. Even 1:10.

Again, 1:7 twist is just as accurate as 1:12 with 55 gr. FMJ, or other moderate to thick jacket ammo.

 

[Robert]

If you have 1:7 forget buying less 62 gr. bullet ammo -- it isn't for you.

So the over 500 rounds of 55gr I have shot at steel, and hit for the most part, out to ranges of 400+m are just all a fluke? Cool! I like it when I defy the laws of the universe.

 

[TonyAngel]

Man, lots of bad information flying around in here. I wonder how many of the guys posting that you can't shoot a 55gr and under bullet out of a 1:7 twist rifle are speaking from experience. If they are speaking from experience, what did they miss when experience was speaking. If they had a rifle that tore a varmint bullet apart, what brand/type of bullet was it? If they had a rifle that wouldn't shoot 55gr bullets accurately, again, what brand and type of bullet was it; and was it true of one rifle or more than one rifle.

The fact of the matter is that you won't know if a particular bullet will shoot in your rifle until you work up a load for it and see. I've had several 1:7 twist barrels that showed a real preference for 52gr HPs at shorter distances.

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.

I do, however, have to admit that I have a theory and have speculated that a 1:9 twist barrel would shoot crappy 55gr bullets better than a 1:7 will. This is only based on the fact that cheap bullets aren't always perfectly round or balanced like good/expensive match bullets and will have a wobble to them, which is exacerbated by the increased rotational speed of the faster twist. It's just a theory and haven't given anything more than thought to it because I usually shoot match bullets when I'm looking for accuracy.

 

[FlyinBryan]

Flyin Bryan has it backwards.

lol @ hocka

 

[ugaarguy]

I do, however, have to admit that I have a theory and have speculated that a 1:9 twist barrel would shoot crappy 55gr bullets better than a 1:7 will. This is only based on the fact that cheap bullets aren't always perfectly round or balanced like good/expensive match bullets and will have a wobble to them, which is exacerbated by the increased rotational speed of the faster twist. It's just a theory and haven't given anything more than thought to it because I usually shoot match bullets when I'm looking for accuracy.

THR member rsilvers alluded to that in a recent .22 LR bbl. twist thread. He does something with weapons development at AAC (based on his posts in the 300 Blackout Threads), and he seems to know his stuff. I think your theory is sound, and probably has been proven. Based ATK's technical bulletens, and the documentation in FM 23-9 I'd wager that US M193 ball is near perfectly round, and well balanced.