1/7 barrels cause bullets to fragment?

[faithmyeyes]

I've been reading through Combative Fundamentals: An Unconventional Approach by Jeff Gonzales of Trident Concepts. In Chapter 23, he asserts that
The 1:7 twist is so rapid that certain types of bullet [...] will literally self-destruct from the high rotational rate upon exiting the barrel. The good news, the 1:9 is the best way to go as it can better deal with a variety of bullet weights across a larger spectrum of uses.

This seems to fly directly in the face of the conventional wisdom on this site, as well as the choices made by the top-tier manufacturers. What gives?

[jmart]

In carbines, 1 in 7" will not cause failure in anything you would typically shoot through a carbine, i.e., 55 grain ball or heavier.

1 in 7" can cause problems when shooting extremely lightweight, light-jacketed varmint bullets, especially when launched at higher velocities from longer barrels. The higher starting velocities translates to increased rpm's and that's what causes the bullets to self destruct in mid-flight.

But if shooting 55/62 ball, 60 grain TAP, 68-75 grain OTM's, 1 in 7" does not overstress these designs.

[ST911]

There are several threads on the topic.

[andre3k]

I have a Savage LRPV with a 26 in barrel 1-7 twist. About half of my 55gr hornady fmj loads dont even make it to the target at 200 yards. This is only one gun with one load though.

[JBnTX]

I have both barrel twists (1/7, 1/9).
Both 16" and 20" barrels.

I shoot out to 300 yds with 55gr, 62gr and
sometimes (rarely) 77gr bullets.

The only difference I've seen is that the heavier
bullets tend to be more accurate at longer ranges.

Other than that, I can't see any difference.

It's another one of those AR "things" not worth
worrying about.

[rat31465]

I have had bullets fragment out of a rifle barrel...but not with my LMT 1/7 twist bbls. The problems I had occured out of an Ackley Improved .22-250 driving 45 grain Sierra blitzkings above 4000fps. The lightweight constructed jackets just wouldnt handle the centrifical forces being placed upon them at such high velocity.
I have some handloads for my LMT that drive this same bullet over 3000 FPS and have never had a frag with them....admittedly though I haven't shot more than 50 rounds of this load yet.

[Failure2Stop]

Unless you intend on shooting very light varmint bullets you are fine.
Stick to proven bullets for the AR platform, which range from 55 gr FMJ to 77 gr SMKs.

[sinister]

Once you start getting substantial throat erosion and some free-bore jump if you shoot light-jacketed bullets pushed fast (like 40-50 grain varmint bullets and J4-jacket Noslers) you may find your bullets vaporizing between your muzzle and 200 yards.

It'll look like a grey puff of smoke and you won't get a hit.

[jar420]

I have seen M193 leave it's jacket in the cardboard backer at 25 meters when fired from an M16A2. Also seen the rounds keyhole more than once at the same distance. My personal opinion after seeing this several times is to keep M193 for a 1/12 twist. The 1/7 really needs 62 Grn +.

SO, there is some truth to what the guy is saying, seen it first hand. It's also possible we had a bad lot, but it was fresh Lake City ball. I kind of doubt that.

[sjc3081]

I've been reading through Combative Fundamentals: An Unconventional Approach by Jeff Gonzales of Trident Concepts. In Chapter 23, he asserts that

This seems to fly directly in the face of the conventional wisdom on this site, as well as the choices made by the top-tier manufacturers. What gives?

This is 100% correct. When I shoot 55 grain projectiles from my 1/7 barrels they always frag. When I look around the dirt piles and rocks that my bullets strike at the 100 yard line. I always find jacket core separation.:D

[faithmyeyes]

Is it fair to say that problems with 1/7 and 55gr ammo is probably limited to higher velocities/bbls longer than 16"?

[Failure2Stop]

Is it fair to say that problems with 1/7 and 55gr ammo is probably limited to higher velocities/bbls longer than 16"?

There is no problem.
Anomolies happen.
Hundreds of thousands of 55gr bullets get pushed into paper through 1:7 barrels in the US every year. The number of complaints related to bullet disintegration dwell somewhere between the number of people that have bad Aimpoints and have seen Bigfoot.

[Iraqgunz]

Bawahhahahhaaahhahahaha. :D My wife was looking at me once with my ACOG and she swore that she spotted Bigfoot as well.



There is no problem.
Anomolies happen.
Hundreds of thousands of 55gr bullets get pushed into paper through 1:7 barrels in the US every year. The number of complaints related to bullet disintegration dwell somewhere between the number of people that have bad Aimpoints and have seen Bigfoot.