M4 Group Size

[LTUME1978]

I have a new LMT M4. I have shot it with 2 different scopes to test accuracy and have been disappointed. I am shooting Lake City 55 grain ammo (the barrel has a 1 in 7 twist and I know that is for 77 grain bullets). I am getting 3 1/4 inch to 4 inch groups at 100 yards off the bench. I emailed LMT and their answer was to try some 77 grain bullets. I plan to do that soon. My question is, what should I expect from a rifle such as this with the 55 grain bullets and what should I expect with the 77 grain bullets? LMT would give no expectations for the 55 grain bullets but said I should be able to get 2 inch groups at 100 yards with the 77 grain bullets.

Thanks

[TDDude]

I have a new LMT M4. I have shot it with 2 different scopes to test accuracy and have been disappointed. I am shooting Lake City 55 grain ammo (the barrel has a 1 in 7 twist and I know that is for 77 grain bullets). I am getting 3 1/4 inch to 4 inch groups at 100 yards off the bench. I emailed LMT and their answer was to try some 77 grain bullets. I plan to do that soon. My question is, what should I expect from a rifle such as this with the 55 grain bullets and what should I expect with the 77 grain bullets? LMT would give no expectations for the 55 grain bullets but said I should be able to get 2 inch groups at 100 yards with the 77 grain bullets.

Thanks

I was just talking about this on another thread. Assuming that the rifle is set up correctly, the bullet weight probably is what's getting you.

The bullet is spinning too fast and that makes it unstable. In extreme cases, bullets can fly apart or at least become distorted due to the centrifigal forces in play; at least that's what I've read.

55gr bullets will shoot much better with a 1:9 or 1:12 barrel.

[The Annoyed Man]

You will definitely notice an improvement with the heavier bullet. But with the M4 profile barrel, I would say that you should be satisfied with 2 MOA. Swap it out to an HBAR with a tight twist like that and your groups will get smaller yet. My son shot 5 rounds into .25" at 100 yards once using an RRA varmint rifle with a 24" bull barrel shooting Black Hills Match 77 grain HPBTs. He carries the cut out piece the target around in his wallet to show off.

Also, try some 65-68 grain loads. With that twist, they likely won't be quite as stable as the 77 grain bullets, but they will shoot better than the 55 grain bullets. To shoot 55 grains, you really need more like a 1:9 twist.

[foo.c]

I've shot a lot of 55 gr factory ammo out of my 1/7 twist M4 clone. I never shot them for groups, but I didn't notice anything unusual either. I do recall the first 3 shots (Black Hills blue box) I fired out of it made a nice cloverleaf at 25 yards.

With handloads (69 gr Sierra Match King, 24.2 Varget, WSR, mixed brass), I can get 3 shot groups @ 100 yards I can almost cover with a quarter.

[RECIT]

Heavier rounds like everyone else has stated will help your situation. I personally can't afford the match type ammo...in any quantity anyway. Is there a reason you chose that rate of twist, or was that just what LMT offered?

[LTUME1978]

1 in 7 is all LMT offers. I agree about the cost of match ammo and will be handloading some heavy bullets. Will update when I get the components and have time to load up and test.

Thanks

[MoJo]

Try some M855/SS109 (green tip) ammo. That's the ammo the M4 was designed for. It's a 62 gr bullet that is long for it's weight because of the steel penetrator that is inside it. The ammo can be found a lot of places online I bought some recently from Ammunition to go.

[Syntax360]

...and M855 is still military surplus ammo - The OPs group sizes may go from 3-4 MOA to 2-3 MOA. Don't run your Ferrari on 87 octane if you expect premium performance - get some premium ammo and I'll bet anything those groups sizes will shrink dramatically. The groups described by the OP sound perfectly reasonable for M193 or M855 military surplus ammo - don't be bummed if you aren't shooting 1 MOA with the stuff. Everyone's gun shoots better on the internet, especially with milsurp ammo.

[RECIT]

... Everyone's gun shoots better on the internet, especially with milsurp ammo.