AR platform rifling twist

[J Everett]

Hey guys, I know a couple of you are a lot more experienced in guns in general and ARs in particular. I'm currently building an AR; it's my second one I've owned but first I've built. I'm open to either building my upper or buying a complete upper if I can find exactly what I want, but I'm leaning toward building right now. My question is about the rifling twist. I've seen everything between 1 in 7 to 1 in 12. In your experience, what's best for firing a 55gr FMJ round in an 18" barrel. I'm not looking for ultimate range (if that were the case I'd be building a .308), but for solid consistent accuracy out to 250 meters or so.

 

[dhyde79]

if 55-62gr is all you're gonna shoot, go 1:9, it's what most off the shelf rifles come with now, 1:8 is a good versatile that handles down to the high 70's low 80's for grain weight but still doesn't overstabilize 55's, and 1:7 overstabilizes 55gr and will handle up to a 90gr. 1:12 I wouldn't use for anything other than something ultra-lightweight like a 35-40gr

 

[jmnielsen]

^^ What he said. I've been told that shooting out to 100 yds and it doesn't really have a noticeable difference, but out past that you will start to see decreased accuracy with a 1:7 twist barrel if shooting 55gr bullets. I primarily shoot 75gr bullets, so I've got a 1:7 that does the job great. I would definitely go 1:9 for your application, maybe 1:8 if you could find one.

 

[dhyde79]

^^ What he said. I've been told that shooting out to 100 yds and it doesn't really have a noticeable difference, but out past that you will start to see decreased accuracy with a 1:7 twist barrel if shooting 55gr bullets. I primarily shoot 75gr bullets, so I've got a 1:7 that does the job great. I would definitely go 1:9 for your application, maybe 1:8 if you could find one.

If you're going 18", just go find a 1:8, there's a company that makes 88gr ultra match ammo that recommends a 1:8.125 if memory serves. You'll be great

 

[J Everett]

Thanks guys. I was leaning toward 1:9 due to it being the most common available. But it never hurts to get some other opinions.