1:6 and, faster twist 556 bbls

[Raffica762]

Thoughts on these 1:5 and, 1:6 bbl twist M4 (ar) bbls from Green Mountain? Anyone even own one? I’ll bet the heavy pills love this twist.

http://www.gmriflebarrel.com/gm-m45-14-25-long-5-56-nato-experimental-1-6-twist-limited-quantity/

http://www.gmriflebarrel.com/gm-m43-10-5-5-56-nato-caliber-barrel-1-5-twist/

 

[Zatoichi66]

A couple guys I shot with had one & swore it was the most accurate AR barrel they had with 62grain. The manufacturer also said they shot great ( we occasionally shot together in NH, but I never got to shoot the 1/6) so the hearsay of the manufacturer & a couple other shooters is all I know.

Wish I had more.

 

[Raffica762]

A couple guys I shot with had one & swore it was the most accurate AR barrel they had with 62grain. The manufacturer also said they shot great ( we occasionally shot together in NH, but I never got to shoot the 1/6) so the hearsay of the manufacturer & a couple other shooters is all I know.

Wish I had more.

Thank you..I’ll bet those Lehigh Defense pills will love those bbls. Not, a bad price..I may pick one up

 

[Potss]

I know highpower guys were doing gain twists that ended in 1:6 or similar.

 

[Raffica762]

I know highpower guys were doing gain twists that ended in 1:6 or similar.

GM only has the 1:5 in 10.5” ..the 1:6 is a 14.25” hmm..thank you

 

[Raffica762]

Thank you for all the input

 

[Rstrick0352]

You can get a 1-6 through X-Caliber for no more than you’ll pay for any other semi-premium barrel. I have several of their .30cal barrels and they’re awesome.

 

[supercorndogs]

62g bullets do not need a 1 in 6 and would not be more accurate because they were shot in that twist rate. 1 in 6 is for super long bullets, most of which are too long to work at AR mag length.

 

[XLR308]

For the twist rate and length they are listing it seems they are focusing on SBR and M4 length rifles running 69-75 grain bullets.
For a 10-14" barreled SBR it would probably be useful but if you don't plan on going that short or using a cartridge that can utilize the long heavies and still fit in an AR mag the standard 1-7 or 1-8 would do just fine.

 

[Raffica762]

You can get a 1-6 through X-Caliber for no more than you’ll pay for any other semi-premium barrel. I have several of their .30cal barrels and they’re awesome.

I have a few Xcaiber bbls very nice

 

[Raffica762]

I take it these fast twist was for the .224 V ..I have heard of 100+ grains bullets

 

[GRIFFIN_ARMAMENT]

I take it these fast twist was for the .224 V ..I have heard of 100+ grains bullets

I have some interest in this. I believe there may be a relationship between the length of a barrel and the ideal rifling for that barrel.

I think more based on a number of rotations to achieve stability than on velocity alone. Granted the green mountain barrels are employing what would appear to be a strategy for short barrel accuracy in conjunction with a .556 chamber which is a conflicting design element.

 

[Yondering]

I have some interest in this. I believe there may be a relationship between the length of a barrel and the ideal rifling for that barrel.

I think more based on a number of rotations to achieve stability than on velocity alone.

That's not how stability works though.

The twist rate is what matters for a given velocity range and bullet; the number of rotations before the bullet leaves the barrel has nothign to do with it. As long as the bullet is following the rifling (which normally happens by the time the full bearing surface is engaged in the rifling), then the bullet spins at that rate, i.e. inches per revolution or however you want to measure it.

Consider spinning a child's toy top. A quick spin with a minimal number of (partial) revolutions is adequate to stabilize it, if the spin is quick enough. On the other hand, wrapping it with string to get a lot of revolutions doesn't make it stabilized if you don't spin it fast enough.

 

[RyanScott]

There is a reason the Soviets put 6 twist barrels on Krinkovs.

 

[Ledzep]

300k-350k rpm in a short barrel with 75's. 350-400+k rpm in a 16-20" barrel.

Too much if you ask me. 300k rpm is where things start turning south. Get a little bit of throat wear, a carbon ring, whatever, and bullets start ripping apart.