1 in 12 Twist

[programmer]

Does anyone sell Ar-15 barrels with a 1 in 12 twist anymore? I want to build another and I want to use 55 grain ball ammo in it. The tight twist of any barrel I've found over stabilizes the bullet.

[k arga]

try white oak armament, they have what you need

[Johnny in Texas]

How can you tell your bullet is over stabalized?

[programmer]

The idea with the original M16 was to provide a bullet that was barely stabilized (1-in-14 twist). This "encouraged" the bullet to upset and tumble thus producing more tissue damage and a larger wound track. In the case of the 55 grain ball bullets the bullet also tends to break in two at the canalure after upsetting thereby producing two wound tracks and increasing lethality. The tight twist of the present M4 produces a stable bullet that has better penetration but doesn't upset as easily. There have been reports that this with the lower velocity from the shorter M4 barrel has reduced the "stopping power" of the 5.56 round. Small varmits can be killed with either one. It's the large 2 legged kind I'm more concerned with. I don't need 500 yard penetration with this round (my M14 will do that). I want the most stopping power inside 200 yards I can get. A 1-in-12 twist barrel is the ticket.

[Johnny in Texas]

I have heard the expression overstabalized bullet but I did not realize it had to do with lethality. I had that problem hog hunting with 55 FMJ's and a 1-7 twist barrel I put 2 shots into a running pig and it did not go down. One in the snout and one in the leg. I ended up chasing it down on an ATV and finishing it off. I use 69gr. HP for hogs now.

[joem]

Try SARCO or Numrich (gun parts Corp). Ohio ordnance had some M16 take off uppers for a while. I bought one of the 1-12 uppers and it was like new.

[togor]

There have been reports that this with the lower velocity from the shorter M4 barrel has reduced the "stopping power" of the 5.56 round. Small varmits can be killed with either one. It's the large 2 legged kind I'm more concerned with. I don't need 500 yard penetration with this round (my M14 will do that). I want the most stopping power inside 200 yards I can get. A 1-in-12 twist barrel is the ticket.

Suggest you leave the 2-legged kind to the authorities.

[leftyo]

1-12 is just about the perfect twist rate for a 55gr bullet, it wont tumble. also dont put too much into the overstabilization theory, i have a 1-9" that is spooky accurate with 45gr bullets. there is really no such thing as overstabilized, it either has a stabilized rotation, or it doesnt.

[bd1]

You just a 60's-70's SP1 or M16 barrel. Look for your best deal.

[programmer]

Suggest you leave the 2-legged kind to the authorities.

Yes, when seconds count, the police are only minutes away.

[programmer]

You just a 60's-70's SP1 or M16 barrel. Look for your best deal.
I have a '70s SP1 but would like one with a late lower and A2 sights. That's why I was going to build one, if I can find a barrel.

[togor]

Yes, when seconds count, the police are only minutes away.

Yes, when seconds count you might need to engage in a firefight at 100 yards with some bad guys while waiting for the police to show up, in which case you'll need that 1/12 twist barrel to keep those 55gr bullets marginally stable for maximum effect whereas a common 1/9 barrel would leave you a dead man for sure.

Talking about optimizing an AR build for maximum human lethality (on an open board, no less) as an ordinary civilian just gives the the anti-gunners another example to point to. You want to do a 1/12 build? Fine, go for it. It's nobody's business why, so try to keep it that way.

[Johnny in Texas]

Yes, when seconds count, the police are only minutes away.

I just renewed my CHL and the Police officer that gave the class must have said that 10 times during the class. I will call 911 with my left hand and call Glock 21 with my right.

[milsurpman]

Yes, when seconds count, the police are only minutes away.

Programmer keep an eye on gunbroker for surplus m16a1 upper assy's. They sometime go cheap. Also look on http://98.196.65.94/retroblackrifle/index.html forum and place a wtb add. Im talking about you getting a good barrel and you having it rebarreled on a a2 upper. The complete a1 would not be bad as you could sell and recoup cost with selling the upper. you should be able to find one in a hurry.
The other guy will find out in a hurry how wrong he is if he ever has a problem.

[milsurpman]

togor when you build a rifle its always for the bullet weight used. The op wants to be in the 52-55 range he needs a 1-12. Most sporting rifles in 223 use this twist for use of light weight bullets. He does not want to use 62 or heavier slugs so 1-9 is out. He will get better rifle results in all performance with 1-12. The 55 is quite stable with 1-12. It was the 1-14 what was unstable in cold temps by gov testing in the very early m16.

[programmer]

Thanks for the info milsurpman and every one else. Togor, blow it out your buttplate. If I want to discuss how effective a rifle or bullet is at killing a criminal I will. Don't you EVER lecture me again on what I can and can't write here. That's not up to you. If you don't like it then leave. I hope and pray I never have to use lethal force to defend myself or family but if I do I want to be sure I use the most effective tool possible. I pity you if you are so scared of what a bunch of anti-gunners think that you want to shush anyone who has the guts to openly discuss things such as this. Now, why don't you go back and hide in the closet and let the adults talk for awhile.

[jmoore]

FWIW: I've been killing deer quite reliably w/ a 20" 1-12 LW barreled AR for a few years now. Its actually quite spectacular w/ 55gr Sierra soft points, esp. under 100yds. Penetration is good, OBLITERATES the lungs, and usually exits. Breaks ribs too. 60gr Nosler partitions work well also, if you are more conservative about possible bullet failures, but I haven't had any yet.

No trick shots, just keeping ranges less than 200yds. Std fwd chest cavity aim.

[Rodd Knox]

Yes, when seconds count you might need to engage in a firefight at 100 yards with some bad guys while waiting for the police to show up, in which case you'll need that 1/12 twist barrel to keep those 55gr bullets marginally stable for maximum effect whereas a common 1/9 barrel would leave you a dead man for sure.

Talking about optimizing an AR build for maximum human lethality (on an open board, no less) as an ordinary civilian just gives the the anti-gunners another example to point to. You want to do a 1/12 build? Fine, go for it. It's nobody's business why, so try to keep it that way.

Really reaching for something. Neither you or I know what the OPs situation is or why he wants this information. I fail to see how he is in the wrong for posting his question unless by doing so he is breaking the law or forum rules.

[snipey8541]

...there is really no such thing as overstabilized, it either has a stabilized rotation, or it doesnt.

I believe the term overstabilized refers to projectiles that are not heavy enough for the barrel twist. Lighter grain ammo has been known to explode when shot through tight barrel twists (1-8" and 1-7"). When your talking about a projectile spinning at around 300,000 rpm, you need to have a heavier mass to keep the projectile stabile. Not saying that this happens all of the time but it has happened.

[rider]

I've had no problems shooting 55gr FMJs through 1-7" barrels. Light, frangible varmint bullets might be another story but I haven't tried them in a 1-7" barrel.

[joem]

I tried 55 gr FMJ in a 1-7 twist and accuracy was some what below my expectations. Next was a 1-9 twist, much better but the 62 gr FMJ really shined. I got a 1-12 20 " upper A1 and it like the 55 gr. The 1-7 twist did really well with 69 gr bullets but cost was a factor, I'm cheap!

[starmetal]

I idea the military wanted a 14 twist to barely stabilize the bullet and eventually cause it to tumble is a myth. Also the stories of smooth bore M 16's in Nam is also a myth. There were very very few 14 twist early M 16's made and they are quite collectible if you can find one.

There's nothing wrong with a 9 twist for a 55 grains bullet. For that matter I have a 7 twist and have found it to shoot just about all weights quite accurately, but the 12 twist would be the preferred twist. It may give you a tad more velocity with equal or less pressure. The benchrest crowds prefer the slower twist.

[Tom in N.J.]

Del-Tron, Elizabethtown, NC stated on one of the forums that they were going to produce a 20", pencil thin, 1::12 twist AR barrel as soon as the blanks came in. These would be perfect for the "retro build" guys.

[rcnixon]

Thanks for the info milsurpman and every one else. Togor, blow it out your buttplate. If I want to discuss how effective a rifle or bullet is at killing a criminal I will. Don't you EVER lecture me again on what I can and can't write here. That's not up to you. If you don't like it then leave. I hope and pray I never have to use lethal force to defend myself or family but if I do I want to be sure I use the most effective tool possible. I pity you if you are so scared of what a bunch of anti-gunners think that you want to shush anyone who has the guts to openly discuss things such as this. Now, why don't you go back and hide in the closet and let the adults talk for awhile.

Programmer for the win!

Russ