Round jamming into feedramp

[Tim K]

This is a relatively new build, less than 100 rounds. When first assembled, the rifle worked perfectly. It's sat for months and been carried in a backpack, but not fired.

It will not chamber a round either with the bolt locked back and using the bolt release or just pulling the charging handle and letting it fly. The bullet gets jammed into the feedramps.

I've looked it over pretty thoroughly and can't find anything obviously wrong. The first inch of bolt travel feels good, then the bolt carrier does seem to drag a bit. Known good Pmags and new Pmags were tried, as was a variety of ammo.

Is there a list of common causes for FTFs?

Barrel is a Wilson, Aero Precision upper and lower.

[J]

Does the barrel extension have the cuts for the M4 feed ramps? If you use an upper with the M4 ramps and the extension is an old A1/A2 on the barrel it can cause jams.

[Tim K]

My bad, it's a White Oak, and it does have M4 feedramps.

[Delfuego]

I had this problem with an AR10 barrel recently. The round was coming up the feed-ramps and smacking the breach-face. The projectile was being crushed back into the case reducing the OAL. The breach-face was re-profiled (angled changed) and the problem disappeared. Not the same problem as your having, but maybe a place to start. I would also look into the angle and polish on the feed-ramps.

[cofi]

can you post a pic of it jammed up??

rifle lower or adjustable?

[cofi]

do you have another lower you can try just for kicks?

[Tim K]

do you have another lower you can try just for kicks?

The gun is in another state, and the owner will swap lowers and BCG tonight.

[cofi]

my thought way a rifle spring in a carbine lowere or the other way around

[Tim K]

Don't think so, but worth checking. I'm wondering if the feed ramps need a little polishing.

[Great-Kazoo]

Just because the mags are new and magpul does not mean they need a little tweaking. The last set i received (Pre airlift) sucked. Feed lips and rear of mag needed a tad of relief. However the biggest issue was the mag did not lock in at all. You think you felt it click in but the cut out for the mag catch was shallow. Cut the mag catch backing piece out [ now looks like an Al mag / see through] and no more issues.

Always check mags first, their the cheapest part of the equation.
My 0.02 dracma's

[bellavite1]

Just because the mags are new and magpul does not mean they need a little tweaking. The last set i received (Pre airlift) sucked. Feed lips and rear of mag needed a tad of relief. However the biggest issue was the mag did not lock in at all. You think you felt it click in but the cut out for the mag catch was shallow. Cut the mag catch backing piece out [ now looks like an Al mag / see through] and no more issues.

Always check mags first, their the cheapest part of the equation.
My 0.02 dracma's

+1.
Had the exact same issue with Thermolds.

[cofi]

+1.
Had the exact same issue with Thermolds.

those things are made of old pringles lids

[Tim K]

The owner did some light filing on the feed ramps, just de-burring. Problem apparently solved. Test fire tonight.