AR-15 Bolt Stop Problem Between Mags

[Cosmoline]

I thought I had this problem figured out but it's apparently more complex than I realized. Or maybe not. I don't know. It's a DPMS upper on a Yankee Hill lower and the bolt stop between magazines only engages as shown in the photo. So when I press the button there's no round stripped off and I have to slingshot it. Not really a serious issue since this is a fun gun, but with AR's sometimes little problems are indicative of bigger ones.

My brass is hitting about where it's supposed to according to those charts for buffer tube strength. And there's no other sign of trouble other than some slight abrasions/chittering marks under the bolt carrier that could be just regular wear.

Any ideas?

 

[paintballdude902]

did you look at the condition of your bolt carrier to see if it has any damage?

 

[Cosmoline]

It's new except for some marks along the bottom.

 

[madcratebuilder]

From the photo it appears the bolt catch is catching the face of the carrier and not the face of the bolt. Short stroking.

What buffer, spring and ammo are you using.

Damaged or defective bolt catch?

Odd to see the catch grab the face of the carrier, the carriers I have are bevel cut at that location so it could not happen.

 

[Bartholomew Roberts]

Are you having any other signs of short stroking or failures to feed? How old are the magazines (and magazine springs) in question?

 

[holdencm9]

If it is short-stroking, wouldn't it be having jams nonstop? If this problem only occurs on the last round of the magazine, maybe it is a lug on the bolt that is rounded off, or the bolt catch itself is defective...either way, it seems the bolt catch slips under the bolt, but is somehow able to grab hold of the BCG.

 

[Cosmoline]

The buffer and spring are what came with the DPMS upper.

Mags are new and there have been no jams at all in about 500 rounds so far. Ejection is to my right and towards the rear about 4-5 feet.

I think what I'll do is swap out the bolt catch and see if that fixes it. That was my initial thought but on close inspection the thing seems fine and works fine when I manually move the bolt. So maybe the bolt is simply going so fast the catch can't grab it in time?

Odd to see the catch grab the face of the carrier, the carriers I have are bevel cut at that location so it could not happen.

That's an interesting point. But I suppose even if I stuck a new BC in there with the bevel cut it would still not be holding open properly between mags. The fact that the bevel is cut in the mil spec carriers makes me suspect this problem has come up before. And they didn't want soldiers to assume they had a round in when they didn't.

 

[Bartholomew Roberts]

The fact that it is shooting normally makes me think the carrier is coming all the way back (i.e. No short stroke). So the two options are that the follower is not engaging the bolt catch fast enough (weak mag spring) or the bolt catch itself is not engagng fast enough.

If you are seeing the problem with different mags, then I'd probably try swapping the bolt catch out.

 

[Cosmoline]

There's no difference between mags so I'll try out the bolt catch swap. That's an easy one to do, anyway.

 

[Bartholomew Roberts]

Hey, you ever work this out?

 

[Cosmoline]

I've stuck a new and better quality BCG in there so we'll see if that helps. I should be able to get out to test it next month at some point. I'm sure a dozen people will offer to buy the rifle from me while I'm there so if it still doesn't work right that's always an option ;-)

 

[animator]

I'm wondering if the wrong spring/plunger was installed for the BHO lever, thus not forcing it up high enough to catch the bolt face, but still high enough to catch the bolt carrier.