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View Full Version : AR-15 w/ an abnormal F to F problem


BMSMA
November 14, 2009, 04:24 PM
Today finished paying off a bushmaster ar-15, brought it home only to discover it had a failure-to-feed issue.

While hand-cycling rounds I discovered the rifle would extract and eject fine, but would jam upon taking up a new round.

I have tested various parts all with no luck...
> Brass and Steel ammo - failure to feed
> Bushmaster GI Mag with MAGPUL follower - failure to feed
> Standard MAGPUL mag - failure to feed
> Swapped lowers with a working AR-15 - failure to feed
> Swapped uppers with a working AR-15 - failure to feed

Here's the strange part.
The rounds appear to get tapered scratch marks on the bullet, were it appears the round is catching on the lugs as they make there way up the feed ramp. I am hesitant to just polish down the lugs b/c I want to make sure that the problems is addressed.

The rounds fail-to-feed but are not jamming. By pulling the charging handle again the round normally chambers completely.

I haven't had the opportunity to field test to see it it happens while firing, but if anyone any ideas. I'm all ears.


Thanks

zoomie
November 14, 2009, 04:25 PM
Do you have M4 feed ramps?

BMSMA
November 14, 2009, 04:30 PM
Do you have M4 feed ramps?

That's a negative.

Gun is a Bushmaster Mod XM15-E2S 5.56 Nato with 1/9 and H Bar

B. Lahey
November 14, 2009, 04:57 PM
Are those mags brand new?

When I took my newest AR to the range for the first time I had a problem like that for just the first few hundred rounds. I think it was a combination of brand new mags and a brand new rifle, the old beater GI mags I brought along functioned perfectly, but the new ones and Pmags seemed to hold onto the rounds with more force.

After a few hundred rounds the mags and the rifle "broke in" and everything has been malfunction-free for the last 5,300 rounds or so.

You may want to make sure that the upper has enough lube, particularly during break-in, and shoot it some more to see if it goes away.

A Wolff extra-power action spring may help overcome the extra friction of a new rifle and/or new mags as well:
http://www.gunsprings.com/index.cfm?page=items&cID=2&mID=1&dID=79

BMSMA
November 14, 2009, 05:07 PM
Are those mags brand new?

I tried both a used Bushmaster GI with MagPul follower and a New MAGPUL Mag both with steel HP and brass FMJ.

Could this be something that just has to work out over time. It is a used rifle and I am unsure how much it has been used.

The deep scratches on the bullet makes me worry a bit.

The gun appears to be in pretty good condition with little use though.

B. Lahey
November 14, 2009, 05:20 PM
ARs have a habit of scratching the projectile as it gets chambered. It's not something to worry about usually.

Lube it generously, take it out and shoot it. Doesn't have to be dripping, but you want lube anywhere there could be any contact, including the entirety of the bolt raceway (tube part of the upper), the little wear spots you will see on the bolt (eventually, anyway), a bit on the lugs, etc...

After you shoot it some, you can go lighter on the lube, but it's a good idea to be generous during break-in.

When the action is operated by firing it will be moving more forcefully than you can move it by hand. You may not have any problems, and the 1st-round chambering problem could go away as the parts learn to live together in peace.

Anyway, it would be a good idea to try it out before changing anything.

B. Lahey
November 14, 2009, 05:27 PM
Also, I would forget the steel-case ammo entirely until you know if the rifle is working properly. Some ARs don't like it and you don't want to mistake an ammo problem for a rifle problem.

Alleykat
November 14, 2009, 06:40 PM
Are you pulling the charging handle all the way to the rear and releasing it abruptly? I'd certainly recommend shooting the rifle, before getting too upset.

BMSMA
November 14, 2009, 06:45 PM
ARs have a habit of scratching the projectile as it gets chambered. It's not something to worry about usually.

That's good to find out. I was hoping to hear that.

I locked and dropped 6 mags worth with no failure to feeds. However it is still having problems with cycling by hand.

I don't have the ammo or the time today to field test it, but I think this avails my fears of having a bunk gun.

I'll be sure to note if I have any problems in firing it.

Thanks guys.

bcarver
November 14, 2009, 06:46 PM
Fire the gun and see what happens.
If it feeds you got no problem.

Bartholomew Roberts
November 14, 2009, 08:15 PM
What Alleykat said, you need to let the bolt slam home and not ride the charging handle as you chamber a round. The rifle can definitely take it.

I'd also second the recommendation to be generous with the lube.

10-96
November 15, 2009, 03:21 AM
+1 on using the bolt release to feed. Let 'er slam home like she was designed. I don't know if any of my 4 models would successfully hand feed- never tried it (I'd be skeered a ghost of a Drill Sgt would show up and start with the push-me-ups and extreme cursing!)

pistolerokid
November 15, 2009, 06:05 AM
I have built several Ar's over the past decade. I would also recommend shooting it for a few hundred rounds first. I had failure to feed with most of them for the first few times to the range. I was shooting PMC ammo. the only way I found to correct was to change ammo in the beginning to a little hotter brand of ammo.