Over the past couple years I’ve upgraded most of my rifles to 1:7 twist rate because it was better at stabilizing the heavier rounds that I shoot occasionally.
But a (non-mil, non-contractor) friend recently asked what was best for him for an all-around AR. I thought about what I shoot: 55gr surplus, 55gr Prvi, 55gr S&B, 55gr LC, and so forth. I do have some 75gr TAP (maybe 300 rounds) for self defense, and I reload 77gr Matchkings once in a while for competitions, but out of the thousands of rounds I’ve shot over the years, they’ve almost 99% been 55gr.
Even if he was interested in a SHTF scenario that the people on OTS like to talk about all the time, I was thinking that the vast majority of ammunition that you would find in stores, on the street, or at people’s homes would be 55gr also, right?
So am I wrong to tell him that for HIS purpose, a 1:9 is prob the more accurate option because it stabilizes the lighter bullets better? Honestly, with his shooting skills he prob won’t notice the difference in accuracy, but I thought this whole exercise made for interesting self-reflection on why I automatically choose the 1:7 whenever I look at a new upper.
I have all 1/7 and 1/8 and mostly shoot 55gr. For 55 and under 1/9 will not put him at any disadvantage. However the only reason I would go with 1/9 is if I planned on shooting lighter than 55 bullets for varmint shooting and such. I personally will not shoot anything less than 55gr so there is no reason to go with a 1/9.
Not in my opinion.
Since comparable barrels cost the same whether they are 1:7, 1:8, or 1:9, it’s not like there is a cost benefit associated with twist changes. Add to that the fact that if he ever does decide to up his game he will be held back by the 1:9.
It seems to me that the most versatile twist rate would be a 1:8.
But that’s just me.
what exactly is the benefit of shooting a higher grain to a lower grain? why would a lower grain be preferable or a higher grain be preferable to some?
Short answer- the heavier/longer bullets tend to provide better precision and superior terminal effect in human tissue.
Smaller, lightweight bullets tend to be oriented toward varmint sized terminal performance, though some options in the 55gr area can be cost-effective for high volume training/practice.
Look around the Reloading and Ammunition sub-forum as well as the Terminal Ballistics sub-forum for specifics and post there if you have further questions.
My 1 in 7 BCM has no problem at all getting center hits on a 3/4 scale steel silhouette at 300 yards with 55 or 62 grain ammunition. I have not seen any tendencies to key hole or tumble at any of the distances I have shot at with the 55 gr. in the 1 in 7 barrel.
The way I see it, if you want to shoot 62gr. and below, get a 1 in 9 twist. If you want to shoot 55 gr. and above, get a 1 in 7 twist. If somebody has any opposing views or experience on this matter I am certainly interested in hearing it. -
I was pleasantly surprised to shoot a couple of sub MOA groups using a Federal 50gr HP bullet and a 52gr Hornady Match HP out of a 7" twist rifle. I would certainly advocate the 7" twist for serious use rifles that will shoot rounds from 50-80grs.
The length of the bullet has a lot to do with the needed twist.
A long bullet needs a tight twist to stabilize. SS-109/M855 has the steel penetrator, which weighs less than an all lead core, so the bullets are long, which need at least a 1/9" twist.
An all copper and lead bullet that’s 60 gr. or so will typically be shorter and may stabilize decently in some 1/12" barrels. The old Winchester 64 gr. Power Point will usually do OK in a 1/12" twist.
Frangible needs the tighter twist because it’s such a light, long bullet.
Here’s the deal. You don’t loose anything on a fighting carbine using a 1/7" twist. You can use 77 gr. bullets all the way down to frangible. If you were building a varmint gun to shoot 40 gr. gopher grenades, you’d want a looser twist.
It’s not just you. 1:8 basically stabilizes anything, and won’t over-stabilize the lighter stuff. 1:7 is another one of those “the military has it, so I gotta have it too!” features. Same with the government profiled, M4-cut barrels. As a civilian, I shoot about as many tracers as I launch fucking grenades, so both of these “features” are not only worthless to me, they actually detract from a rifle’s functionality.
Not an opposing view, but just want clarification for myself in learning the twist rates. By what you said, would you suggest a 1:8 twist if a person were to only use 55gr. - 62gr. ?
I’ve only seen this on intenernet heresay and such but isn’t there supposed to be an optimal twist rate of 1:7.7, to which 1:8 is the closest and recommended as the best average?
I haven’t owned one, but I think that a 1 in 8 twist would probably be optimal. Kyle Lamb says so in “Green Eyes and Black Rifles”, and Failure2Stop (who is usually right on the money with his recommendations, so I listen when he makes a comment) suggested it as well.
I just wish more mainstream manufacturers would offer barreled uppers in that configuration.
