AR-10 suddenly stops feeding, even first shot from magazine

[The Dumb Gun Collector]

Hey

I was zeroing a buddies' Wilson AR-10 when it suddenly stopped feeding. I mean every damn shot was getting jammed at the base of the ramp. It was feeding absolutely fine for the first 10-12 shots. I swapped out ammo and not a single shot Ould get up the ramp...even FMJ. We swapped mags and same issue. Clues? Speculation? Again, this isn't the gas system, it won't feed the first shot out of the mag whether you cycle it manually or drop bolt for bolt release.

[uffdaphil]

Could something be causing the mag to be slightly canted even though it locks into place? Debris or a burr knocking the round to one side a bit as it is stripped? You did ask for speculation.

[Send it...]

Is the mag seated higher than it should be? Insert firmly, then pulldown on mag, then shoot it.

Or where you using it for a monopod?

Sometimes pressure up on the mag can cause rounds to rub on bcg. Also, any way the hammer is rubbing on bottom of bcg for some reason?

[The Dumb Gun Collector]

I was using it for a monopod at first. After it started malfunctioning I stopped. Also remember, this was happening on a locked back bolt. I literally couldn't get any ammo to feed from a mag.

[Send it...]

I was using it for a monopod at first. After it started malfunctioning I stopped. Also remember, this was happening on a locked back bolt. I literally couldn't get any ammo to feed from a mag.

No gun plumber here, but I would separate the upper and lower and try inserting the mag into the lower and push up mag like it might be when using it as a mono pod. If the mag goes in deeper than the normal notch, I'd try putting another twist or two on mag release. If that does not work, I'd try another mag release. I have a bunch in a bin. When you look at many side by side you will notice that they have some variation from part to part. Look for one with a lil longer hook to hold mag in place if that makes sense. I might also try another mag release spring....

[B Cart]

Do you have other mags to test? Are other mags having the same issue? I would start there and rule out the mags first.

[DwayneZ]

Did you happen to save the brass from the 1st 12 that did feed ok? Any odd marks on them?
What about jammed cases, what do case markings look like? Look closely all around the case from bottom to top.

Also take bore scope (any scope) and inspect the throat and chamber area for any odd things.

[bfoosh006]

What specific brand mags did you try ?

What specific brand ammo ?

How many rounds fired thru the problem rifle ? Lubed well ?

And any marks on the brass ? That will help us figuring it out.