which is more accurate,1:7 or 1:9 twist?
depends what ammo you want to use. 1:9 twist is ideal for 50gr-55gr ammo and 1:7 was design to shoot military type ammo of 62gr-69gr+.
You can shoot either or with either barrel but for optimal performance you would want to choose the right bbl for your desired ammo. I shoot 1:9 and mostly shoot 55gr JHP for varmit but I seem to shoot my 69gr powerpoints just fine. I think that shooting a 69gr through a 1:9 would just cause the bullet to start tumbling sooner which may effect your 300yd+ accuracy. I’m sure the gurus will chime in soon…
I’ve heard that it’s good to match twist to weights but then I’ve also heard anecdotal stories about 1x7’s that shoot 50-55 grain bullets better than 75-77 grainers.
I would put more faith in the manufacturer of the barrel rather than the actual twist.
Choosing the right ammo is more important than twist
There are many in depth articles on this.
Here is one source, with links to others.
http://anarchangel.blogspot.com/2007/01/stabilization-mythology.html
From Link:
"Of course the most common rifle chambered in 5.56, and the rifle which engendered this discussion, is the AR-15/M16.
The original AR15 specification used a 1:14 twist barrel, and 55gr bullets. It was this twist rate and loading which created the “M16 bullets tumble” myth, because the 55gr bullets were not fully stabilized with rifling that slow.
The rifling twist was shortened to 1:12 with the M16A1, then to 1:9 with the A2, and finally 1:7 with the A3 and A4; specifically to support longer bullets such as tracers (not to support the standard 62gr bullet, which will stabilize just fine at 1:9)."
M16A2’s had 1x9 twists?
I hadn’t known that. Berry berry interesting.
m16a2’s were/are 1/7 twist, the errornet strikes again.
my SP1 is 1/12 and is very accurate with 55 grain and 62 grain. and yet my 1/9 Colt 6724 loves 75 and 77 grain . check the AMMO Orical for the low down .
Another error from that stupid link is that 1/12 doesn’t stabilize a 55gr bullet. 1/12 stabilizes 55 grain just fine. In fact, as a general rule, 1/12 gives optimal accuracy for 55 grain projectiles.
that’s what I have observed,the 1/12 is perfect for XM193 or Q3131a.
One thing I am trying to get a better handle on is twist rate and bullet stabilization at long distances - practical experiences, not theorethical exercises. I had a similar post on another thread - so I’m repeating myself here a little. I’m not talking 100 yards, I’m talking a much longer range.
For example, with my 1/9 twist 16 in barrel, with 55gr M193, I can get sub MOA at 100 yards on paper and can hit 3ftx3ft and 2ftx2ft gongs out to 600 and 650 yards with no problem.
My 1/12 twist Browning bolt action (.223 chamber) w/22 in barrel does not handle ANY 55 gr .223 load that I have tried well at all. At 100 yards at best I get 1.5 inch groups with ANY load. I’ve tried 50 gr too and the improvement over 55 gr is marginal. But with 45 gr it becomes a tack driver (at least in my definition and my abilities) with consistent 3/8 in groups at 100 yards and 1 inch groups out to 300 yards on paper targets on a windless day. I have not put bullet to paper with this gun past 300 yards. I have not shot M193 thought this gun as it is chambered .223 and not 5.56, so I don’t want to get into a chamber pressure issue.
So - when people say that 1/12 stabilizes 55 gr, or 1/7 stabilizes 55 gr just fine … my question is: at what ranges and at what level of accuracy at those ranges? I am curious as I am about to pick up a 1/7 and am interested in people’s experiences with 193 at long ranges (ring the gong or put a hole in the paper is the only objective at those ranges).
Depends on a lot of variables: type of ammo, manufacturer of the barrel/weapon, whether it’s a match or stock barrel, skill of the shooter (the most important variable IMHO), ect… The 1:7 barrel will give you the largest range in types of bullet weights. 55-75 grain and higher. My 1:7 barrels shoot 55 grains pretty accurate. More accurate than some 62 and 75 grains. YMMV.
Pictures are worth many words and each rifle is unique.
Colt M4 Target, w/ 1-7 twist rate. 5 shots 100 yards with ACOG TA01-NSN 4x32
and 55 gr American Eagle. Make shift rest on range bag.
She’s a keeper.
Individual barrel quality and ammunition consistency will play a larger difference in applied accuracy than the difference between 1:7 and 1:9- as long as each is fed the appropriate ammunition.
no matter what anyone says it is all up to your gun… most 1/9 will shoot 75gr fine… mine does, if you are going to be shooting alot of 800m + stuff then a 1/7 is for you if you are only going to be shooting 800+ once in a while 1/9 will be fine… I have not found a 1/9 yet that will not shoot 75gr ammo and 1/9 twist will wear better. you can tell by shooting at 100 yards and if you keyhole then your gun will not shoot that ammo… I would not go past 77gr with a 1/9. and it really is only worth going with 1/7 if you are going to shoot 77gr ammo more then 50% of the time… and as for accuracy you will want a 1/8 match grade barrel… it is more about how well the barrel is made then the twist… I have seen 1/10 shoot better then 1/7
My HB Varmit with a 1:8 twist shoots better then my 1:7 or 1:9.
The 1:8 doesn’t like the lighter rounds but shoots the hell out of the 69 & 77’s
I have a 24-inch Bushy Varminter that has a 1:9 twist and likes the Black Hills (Blue box) 75-grain BTHP. I have shot this combination out to 926-yards with great effect (as long as I do my part).