how about 50 grain?
how about 50 grain?
Not at all. Our military has used Colts (1 in 7) twist with 55 gr. ammo since about 1963.
Another great thing about the 1 in 7 twist rate is that those barrels will shoot any ammo you put through them-- from 55 gr. to 75 gr.
Coltman is correct. the faster twist rate is typically used to stabilize heavier rounds, but it isnt "too much" for ligher rounds. its a great all-around barrel for whatever you may want to feed it.
The twist rate for the first few decades of the AR15/M16 rifles' existance was not 1 in 7 but rather 1 in 12. When the 55 grain loadings began to be dropped in favor of various loads using heavier bullets then the twist rate was tightened up.
My stock 1974 Colt SP-1 AR15 has a 1 in 12 barrel. It is fine with handloads using bullets up to 62 grains in weight. I've not attempted to load anything heavier.
The quicker 1 in 7 twist might shoot the 55 grain loadings such as the M193 very well or even shoot lighter weight bullets than that. One would need to experiment. The handloader could probably devise a load that would shoot most any bullet weight down to 40 grains in a 1 in 7-inch barrel but might not get really fine accuracy with the lighter weights due to the fact that the bullets could be said to be over-stabilized.
My 1-in-12 Rem 788 works fine with 55 grains, but I've never fired anything heavier to see what happens. For what I was shooting the 55'ers were heavy enough.
I love the 1 in 7 twist in my Colt. So far I've only shot 55 grain but it shoots it very accurately. I also like the fact that I can shoot up to 77 grain bullets. I plan on getting some heavier rounds for defensive purposes.
OP, 55gr is about the lightest weight bullet I would use in a 1:7. And it doesn't really have anything to do with power, it has to do with the amount of spin put on the bullet for its flight. Lighter bullets have can be de-stabilized with a faster twist.
Love the notion of the Remington Model 788 rifle, OldVet. It's one of those happy accidents where a rifle made to an economy design gave a performance all out of proportion to it's cost. The excellent action design is said to have the very fastest lock time of any bolt action rifle ever made. Remington barrels of the era seemed to be uniformly good, producing really nice accuracy. I think Remington ultimately killed the Model 788 because it was cutting into sales of their bread-and-butter Model 700 too much.
We used to hold informal bench rest competitions in a gun club to which I belonged for many years. The boys who had trick Model 788s came in for more than their share of trophies. Other than the occasional barrel change-out to something stiffer, they mostly installed more usable trigger units. Great rifles!
I want one now.
My Colt SP6920 likes the 55 gr M193 rounds just fine, and I've never heard of anyone having problems with 55 gr out of such a barrel. I may use a 1/9 or something if I wanted to go any lighter than that though. I suspect with the lightest bullets it would still be alright, just not ideal.
I have tested the accuracy of 50gr, 55gr, and 62gr bullets through my Colt LE with a 1:7 twist rate and cannot tell a noticeable difference at all. The only time I notice a difference is when I use Tula ammo as opposed to a higher quality round. The Tula opens up my groups by about an inch at 100 yards.
Choosing an AR15 Barrel Twist Rate
Valhalla Tactical Supply
I had the same question several years ago when I built my AR. I used a White Oak Arms 1:7 barrel. It took a few rounds for the stainless barrel to break in, but I'm now delighted by the way this barrel handles 55gr. bullets. Heavier, bullets too, of course. :)
i'll test the 50s this weekend