New to AR's, Few Issues

[jdbell2004]

I bought a used Bushmaster M4 A3 16in barrel 1/9 twist. I'd been having trouble getting it to group well at 100 yards. Today I shot groups with Remington UMC Hollow Point 50gr and Winchester Supreme Silver tip 50gr. Both grouped about 1.5-2 inches at 100 yards. I was shooting from sitting unsupported with my drop down grip resting on the bench. I was able to keep it very steady. My foregrip is not free floated.

I noticed after unloading my rifle that the bullets are gouged after being chambered. I believe its the feed ramps that gouge the bullet. Could this be causing my loose groups or is 1.5-2 inches acceptable to most people?

Here is a picture of the gouged bullet, my fingernail would catch the gouges.

http://i33.photobucket.com/albums/d100/jdbell2004/100_0963.jpg

Jon

[Jay Cunningham]

A 1.5" group at 100 yards with an AR carbine is really good. I don't know what accuracy you were expecting but IMO you should be thrilled.

[geminidglocker]

What Katar said.

[matt86]

given a persons head is 5-7 inches wide, id feel comfortable with that.

[JonnyVain]

...especially with UMC.

[spamsammich]

...and those scratches are normal when you eject a live round from the chamber. I don't recommend doing this, but to prove a point to myself I dropped a fresh round in the chamber, moved the bcg to battery with the forward assist, then ejected the round and ended up with scratches just like those.

[Reddevil]

Perhaps shooting 56-62gr ammo might close up a bit more?

[jdbell2004]

...and those scratches are normal when you eject a live round from the chamber. I don't recommend doing this, but to prove a point to myself I dropped a fresh round in the chamber, moved the bcg to battery with the forward assist, then ejected the round and ended up with scratches just like those.


I tried that and yes I got scratches, but I also tried removing the extractor and firing pin from the bcg, loaded a round into a magazine, chambered the round, pulled the bolt back, let the round fall out and there were deep gouges in the bullet. Those were from being fed into the chamber and not ejected. Could you try this? Is it normal or ok for the ramps to chew the bullet up like this?

[Whootsinator]

From everything I've read here on M4C, your experiences are normal.

[spamsammich]

I tried that and yes I got scratches, but I also tried removing the extractor and firing pin from the bcg, loaded a round into a magazine, chambered the round, pulled the bolt back, let the round fall out and there were deep gouges in the bullet. Those were from being fed into the chamber and not ejected. Could you try this? Is it normal or ok for the ramps to chew the bullet up like this?

No, I'm not going to try it because it is normal and nothing to worry about.

[fatboyR6]

My Stag does the same thing it scratches the bullet. I do believe M4 feed ramps may help this. I dont have M4 feed ramps, but have never had a single problem with my Stag with over 1500 rounds threw it. Also I agree that 1.5-2" groups is awesome with no free float and a 16" barrel. Is that with Iron Sites? If yes, then you are the man!!!

[spamsammich]

My Stag does the same thing it scratches the bullet. I do believe M4 feed ramps may help this. I dont have M4 feed ramps, but have never had a single problem with my Stag with over 1500 rounds threw it. Also I agree that 1.5-2" groups is awesome with no free float and a 16" barrel. Is that with Iron Sites? If yes, then you are the man!!!

No, M4 feed ramps don't help. Every barrel extension I've used does this, from LMT to Noveske. Molon puts down VERY impressive groups with his Noveske barrels so I'm confident that the scratches do not influence accuracy enough to worry about.

[fatboyR6]

No, M4 feed ramps don't help. Every barrel extension I've used does this, from LMT to Noveske. Molon puts down VERY impressive groups with his Noveske barrels so I'm confident that the scratches do not influence accuracy enough to worry about.

I wasn't sure, so thanks for clearing that up.

[ca_fireman19]

Perhaps shooting 56-62gr ammo might close up a bit more?

Doesn't this require a 1:8 or a 1:7 twist rate?

[arizonaranchman]

Normal.

Here's something I did and it made a big differece on all 3 of my AR's. Mine all scratched the bullet the same way and sometimes even the brass casing a bit.

I used a super fine piece of emory paper and wrapped it around the last few inches of the handle of a thin modeling paintbrush.

Remove the upper reciever and remove the BCG. Using the emory paper BY HAND - NOT A DREMEL or power tool, I pressed the emory paper into the channel of the feed ramp and spun the paper left and right to just remove the burrs on the edges of the steel feed ramps. I carefully avoided the aluminum m4 portion of the feed ramp on the reciever as you don't want to remove that protective coating of black oxide finish.

It only takes a few minutes. You aren't trying to make it a mirror finish by any means at all. You're just taking the sharp edges off that cut steel is all you're trying to do.

Once I've done this my bullets/brass have almost no scratch at all and the guns feed slick as snot.

I reload so "why do you care if the casing is scratched" might be asked by some. Brass longevity I guess is the only reason for me and maybe a mild case of OCD, lol.

[Jabroni]

No, M4 feed ramps don't help. Every barrel extension I've used does this, from LMT to Noveske. Molon puts down VERY impressive groups with his Noveske barrels so I'm confident that the scratches do not influence accuracy enough to worry about.

I agree with spamsammich, that the scratches aren't a major factor in your accuracy. I personally think the majority would call the grouping good with the gun and ammo you used.

You could experiment with different ammunition to see if you can find one that groups more to your liking(perhaps a heavier bullet 55-62gr. such as Reddevil suggested). But, the improved accuracy(if any) might not be worth spending the money on some high end ammo. I guess it depends on whether you think it's worth it or not.

All-in-all, I think matt86 said it best,


given a persons head is 5-7 inches wide, id feel comfortable with that.

[Thomas M-4]

The scratches on the bullet are normal and should have no effect on accuracy.
There was a precision shooting magazine article I believe that showed damaged tips on bullets had almost no effect on accuracy now damaged bases would did have an effect on accuracy.

1.5'' Sound about right for a M-4A3.

[Jay Cunningham]

If it ain't broke, don't fix it.

1.5" out of your Bushy is more than getting it done. No reason to screw with it or "work" on it, IMHO.

[Lee Indy]

try some other ammo brands may get better.

[Iraqgunz]

Seriously? I am not trying to be an asshole, but as others have said 1.5" from a stock type carbine is very good. I seriously doubt that he can improve much on that at all.


try some other ammo brands may get better.

[NCHornet]

No issues at all and it sounds like you are getting good groups from a semi auto Carbine. You want tighter groups get a bolt action.

NCH

[CAVDOC]

1/9 twist should be good up to 69 gr bullets and depending on the barrel may still shoot 75gr ok too.

[thopkins22]

but I also tried removing the extractor and firing pin from the bcg, loaded a round into a magazine, chambered the round, pulled the bolt back, let the round fall out and there were deep gouges in the bullet.

Don't remove the firing pin and put the carrier in the upper again...you'll have a not so fun situation on your hands.;)

[jdbell2004]

Don't remove the firing pin and put the carrier in the upper again...you'll have a not so fun situation on your hands.;)

What happens?

[thopkins22]

What happens?

The firing pin hold the cam pin at the right angle. Without it, the cam pin can turn the wrong direction and lock your BCG up tight in the upper.

[jdbell2004]

Oh, ill not do that again. Thanks!