Rifle length gun, some issues

[jwfuhrman]

Trying to diagnose some issues with my buddies 3gun rifle. 18in BCM SS410 barrel, BCM BCG, Rifle buffer system, PMags.

He is a cheap son of a b and uses what ammo he can get (usually UMC 55's). But this last weekend he used Hornady steel match ammo and was still getting double feeds, over rides, and failure to lock back.

I took his gun home with me, and after numerous different mags and ammo I had 0 issues with my hand loaded 55gr(nato replicated), American eagle 55's and wolf 75gr(had failure to lock back but no other issues).

I'm wondering if all of his mags combine with the shit UMC ammo are just junk. Or if possible the gas port is slightly undersized(what should correct size be so I can check?)

[KrampusArms]

The gas port in BCM rifles is of a diameter to work best with 5.56 Nato ammunition. Thats my guess, and most likely the problem as evidenced by your nato replicated ammo working in his rifle.

[Robb Jensen]

I use a CAR buffer with a standard strength CAR buffer spring with my 18" SS410 rifle gas barrel and have no issues with 75gr Steel Match Hornady ammo in my 3 gun rifle. I'm also using a JP LMOS 6 oz carrier.

[constructor]

The gas port in BCM rifles is of a diameter to work best with 5.56 Nato ammunition. Thats my guess, and most likely the problem as evidenced by your nato replicated ammo working in his rifle.

Agree,
port on a rifle system to shoot weaker ammo may need to be .093 or even .096.
make sure the gas block port is aligned over the barrel port then check the ammo he wants to shoot 1 at a time to see if it locks back.

[jwfuhrman]

The gas port in BCM rifles is of a diameter to work best with 5.56 Nato ammunition. Thats my guess, and most likely the problem as evidenced by your nato replicated ammo working in his rifle.

Thats what I was thinking as well. I'm taking the upper into work with me tomorrow so I can check the gas port size. If need be I will enlarge it one size at a time until it functions with the crap he shoots.

[Tweak]

When you say Double Feed are you talking about two live rounds trying to feed or one fired round and one live round?

Always short stroke test malfunctioning rifles.