I have a M&P15 and was just wondering what is the heaviest grain bullet I can use in a 1/9 twist and what grain is most accurate in 1/9 twist? Thanks
Probably about 69 grains. Some people have said they can get 75 grains to fly straight.
Every rifle in the world is unique. The easiest thing to do is simply buy a box of heavy bullets. There are no flat rules that say it can’t work. The worst that can happen is that it’s not all that accurate at 200+ yards. My M&P15 is also a 1:9 twist.
I’m not into competition shooting or marksmanship events where the 75 grain match bullets are more common. I don’t live in a state where you are allowed to shoot deer or big game with a .223/5.56 (Our deer are too big). So; being I shoot basically 55g and 62g, I’ve never had a need to shoot heavier or worry about the barrel twist. But I did experiment with a couple of boxes of 75 grain Hornady TAP ammo through it. Just to see how it would perform in case 75 grain ammo was all I could get. I also shot some wolf 75 grain to compare. I didn’t try shooting 200+ yards. Why? Because that’s not what I would normally shoot, so why experiment with something I don’t do. I shot like I always do. 100-125 yards. Iron sights and red-dot 1x (Basically open sights). Total purpose: Would I hit a person if I was aiming at them? The answer is yes.
I had not problems getting all the rounds to land in a 4"x4" square area. Just like it does with the 55 and 62 grain I normally shoot. I will say that it “APPEARED” to be on the edge of keyhole impact. If I was shooting at 200-300 yards, it probably would have been much more noticeable.
So what does this tell me? I am not a Military sniper trying to shoot at 300+ yards. I am not into competition or marksmanship shooting. I plink for fun, and to be prepared to shoot people if necessary. Therefor, if a case of 75 grain wolf or bear ammo was on sale cheaper than 55 or 62 grain ammo, I definitely WOULD buy it. Too many people think that 75 grain ammo simply “WON’T WORK” in a 1:9 barrel. Like it’s going to blow up or something. The 75 grain bullet is longer. It’s heavier. It doesn’t have as quick of a chance to get up to full rotation of the bullet in a 1:9 twist as it can with a 1:7. But for the average shooter out there; or the dear hunter at 100-125 yards, the 75 grain bullet will work just fine. But again; each weapon is unique. You need to try it in your rifle.
From experience I believe it depends more on the pill and the reloader imho … at least up to a point.
There are some spitz soft point heavier pills out there that I cannot get to fly straight no matter what I do. I have to get down in the 62 - 55 weight class for those out of a 1:9 but they do major damage to yotes.
At the same time I can roll’em hot on top of 24 grs of H335 and CCI #41s with either the Nosler 53065 in 69 grs or the Hornady 2278 in 68 grs and they do well in both of my 1:9s.
I like heavier bullets. I really believe that you are pushing the limits of any M4 carbine with 1:9 twist rate when you go about a 69 grain pill. I am also pretty sure that you start to get into compressed charges with anything bigger on most of your common proppelents plus Hornady, Sierra, Nosler, all of them that offer-up the 75s, 77s, 80, etc., they all recommend 1:7 barrels for a reason.
These are my favorites, and the heaviest I’ll go in the carbines:
Thanks for the comments guys. I just wanted to get some opinions from people who have experimented with different grains in a 1/9 twist.
If anyone else has anymore comments I would appreciate it. Thanks
1/9 twist barrels are not as far as I know as consistent as 1/7 twist. So you will have to buy some of the others and test them.
I only shoot 1/7 and from all the shooting I have done they are across the board more consistent and will reliably shoot from 55gr.-77gr. w/o problems.