New AR- FTF

[Newbomb92]

Have a new build I never got out to shoot, Wilson Combat lower, PSA M4 upper, all quality parts. Using Pmags and Steel mags. Cycling ammo through this rifle, it fails to feed. The round will start up the ramp, then stop unless I hold it back and let it slam the round in. My other PSA/BCM/etc builds don't do this. I can ride the charging handle all the way home and it still completely closes. The BCG is well oiled. Here is a pic...the M4 ramps don't look right to me.

 

[cwillour]

What gas length and buffer? Barrel length? Ammo?

You mentioned it has no problem if you manually bring back the bolt and let it drop home? If that is the case, I wonder if you could be marginal on the cycle and just not enough force to bring the round home?

 

[Newbomb92]

Yea it starts to chamber the round then gets hung up. Locking the bolt back on a full mag, hit the bolt release and it goes fine. It's a PSA upper, 16'' carbine length, any ammo, standard buffer.

 

[cwillour]

What happens on a last round in the mag? Does the bolt hold open or does it drop close?

Also, any sign of carbon near the gas block? (I doubt there would be, but just in case ...)

 

[phylodog]

Locking the bolt back on a full mag, hit the bolt release and it goes fine. It's a PSA upper, 16'' carbine length, any ammo, standard buffer.

Then it is working just fine. You aren't supposed to ride the charging handle forward.

 

[Newbomb92]

I understand that. It's the first build I've done that won't feed while riding the charging handle home.

 

[Newbomb92]

What happens on a last round in the mag? Does the bolt hold open or does it drop close?

Also, any sign of carbon near the gas block? (I doubt there would be, but just in case ...)

It's never been fired. While manually cycling it, the bolt does hold open on an empty mag.

 

[indyjohn]

I don't think the ramps look right either. I'm curious what the bullet looks like after you've chambered it in the way you described "let it slam the round home". Seems to me if it has a gouge in it, I would wager there's a manufacturing fail. But I'm not the sharpest tool in this shed.

 

[phylodog]

I understand that. It's the first build I've done that won't feed while riding the charging handle home.

Some surface(s) is creating enough parasitic drag that it won't allow the BCG to push the round into the chamber unless it receives the force designed for this purpose from the spring. I guess I don't understand the concern, the rifle is functioning as designed.

 

[Newbomb92]

I don't think the ramps look right either. I'm curious what the bullet looks like after you've chambered it in the way you described "let it slam the round home". Seems to me if it has a gouge in it, I would wager there's a manufacturing fail. But I'm not the sharpest tool in this shed.

I did notice a scratch in the bullets. I'm going to run a few mags through it tomorrow and see if maybe it's just tolerances needing to be "broken in".

 

[cwillour]

I'm with Phylodog, I would not expect it to run smoothly riding the charging handle. It may be that the feed ramps could use some break-in, but unless it give short-stroking or FTF issues in use I would not be concerned.

The ramps look pretty normal to me, although I cannot tell if it is just lighting & reflections in the picture or if they are a little rougher than I normally see. Either way, a good break-in should go a long way towards sorting the issue out.

 

[j706]

I have had quite a few different firearms that while manually working them fail to function properly. I believe they need to be worked like they are designed to work. IE: don't baby the things. They gotta have that bolt speed ect.

 

[indyjohn]

I did notice a scratch in the bullets. I'm going to run a few mags through it tomorrow and see if maybe it's just tolerances needing to be "broken in".

phylo knows what he's talking about. Rereading you OP and his replies, you may want to do a bit of filing of the ramps (youtube video) to achieve what you're trying to do.

None of the ARs I've owned would chamber a round in "slow motion" by riding the charging handle.

Edit: scratch doesn't count, you'll get that just from exiting the mag. I'm talking deep gouge into the jacket from tip to the end of the ogive.

 

[Newbomb92]

Here's a couple more pics...It seems like the bullets are getting tore up when feeding...

 

[Newbomb92]

I understand but it doesn't feel right, I'll have to test fire it in the morning.

 

[mvician]

STOP hand cycling live ammo. Load the rifle the way it is meant to be.

 

[evsnova74]

STOP hand cycling live ammo. Load the rifle the way it is meant to be.

Yeah I was gonna say, aren't you getting little dimples in the center of the primers, OP? My heart sunk the first time I saw that...

 

[churchmouse]

I had one do this as I cycled it through the mag. The ramps looked just like that. The nose of the round would catch in the ramp and not feed.
I polished the feed ramps with a Craytex stone in a dremel. Not removing a lot of material but putting a nice finish on them. Bingo....off to the races.

 

[indyjohn]

I had one do this as I cycled it through the mag. The ramps looked just like that. The nose of the round would catch in the ramp and not feed.
I polished the feed ramps with a Craytex stone in a dremel. Not removing a lot of material but putting a nice finish on them. Bingo....off to the races.

This is what I was thinking too. Wonder if he got to fire it.

 

[Colt556]

The rifle seems to be functioning the way it was designed to function. Plus it's a new and unfired rifle so it needs to be shot some so everything starts to work in. Let us know what happens during and after shooting a couple hundred rounds. Are those metal shavings in the picture or lint or something else?