I could use some diagnosis help, please.

[Robocop1051]

Proof that any problem you experience, we have already troubleshot, and can be referenced in our archives. 

[98Z5V]

6 minutes ago, Robocop1051 said:

Proof that any problem you experience, we have already troubleshot, and can be referenced in our archives. 

^^^  Truth.   I think the newest goldmine is the information on the AR15 Pistol Caliber Carbines, with buffer weights and springs, and the .40 chamberings above all else.  That shiit is gold. 

Edited June 15, 2019 by 98Z5V

[DustinIL]

10 hours ago, 98Z5V said:

We did a ton of BCG measurements in a thread here, and I can't find the damn thread to save my life right now.  You should use that thread for reference - if it can be found...  

EDIT - here's the thread with the BCG measurements, and a ton more info:

 

Thank you very much! I tried looking for the specs using the site search (I even read the thread on how to do it right, lol) and wasn't having any luck.

[DustinIL]

8 hours ago, Robocop1051 said:

Proof that any problem you experience, we have already troubleshot, and can be referenced in our archives. 

I totally believe it and am most appreciative of the wealth of knowledge and help you guys have given me.

[DustinIL]

On 6/14/2019 at 12:58 PM, Robocop1051 said:

I think your carrier is out of spec. The carrier is contacting the charging handle just enough to keep the CH in line with it while cycling. 

This could be from upward pressure, or out of spec area around the circumference of the carrier. 

Try a borrowed BCG, or at least a carrier. 

Also try single loading one round, and firing with no magazine in the rifle. 

Both of these are rare, but we need to eliminate everything. 

Update:  Just got back from the range. I started with 5 rounds loaded without magazine inserted and using a buddy's DPMS BCG. Near as I can tell the charging handle didn't move back (was by myself so no way I could possibly record on phone and try to slowmo); had it braced against my bicep so I could keep my head back to watch.

Second 5 rounds I used a magazine... charging handle for sure moved back. Magazine was not resting on table during shots. Moved during all 5 shots. For last 10 rounds in box I fired without magazine inserted. No movement as far as I can tell. Even shouldered normally and put a finger in front of CH to check for movement, none noticed.

Magazine used was a 20 round pmag (few years old, but barely used). So I'm guessing either mag lips too tall for the DPMS lower? Or not enough space in upper where BCG and charging handle are on top of mag while I'm battery?

What's my next move?

Oh yeah, almost forgot. I had also put some white touch up paint on underside of CH and so no signs of rubbing or other contact.

 

[Robocop1051]

Let’s try to do this on the cheap as possible route. Have you ever bought an Accu-Wedge before?

https://www.brownells.com/rifle-parts/receiver-parts/receiver-hardware/accu-wedges/brownells-accu-wedge-sku080000663-27507-53257.aspx?rrec=true

It’s obvious that your carrier is grabbing the CH somehow. The upward pressure from the wedge might be able to separate the receivers just enough to eliminate that.  It’s a $5 experiment. The wedge has to be cut to fit. I used a loose razor blade to shave off very thin layers till my receiver squeezed together tightly  

I “polish” (for lack of a better term) all my charging handles with 0000 steel wool. I hate the course anodized finish, so I put a thin layer of lube and then I rub the CH down till it’s smooth. This added bit of attention might assist with your carrier too. Especially if you’re using a phosphate carrier. 

[DustinIL]

1 hour ago, Robocop1051 said:

Let’s try to do this on the cheap as possible route. Have you ever bought an Accu-Wedge before?

https://www.brownells.com/rifle-parts/receiver-parts/receiver-hardware/accu-wedges/brownells-accu-wedge-sku080000663-27507-53257.aspx?rrec=true

It’s obvious that your carrier is grabbing the CH somehow. The upward pressure from the wedge might be able to separate the receivers just enough to eliminate that.  It’s a $5 experiment. The wedge has to be cut to fit. I used a loose razor blade to shave off very thin layers till my receiver squeezed together tightly  

I “polish” (for lack of a better term) all my charging handles with 0000 steel wool. I hate the course anodized finish, so I put a thin layer of lube and then I rub the CH down till it’s smooth. This added bit of attention might assist with your carrier too. Especially if you’re using a phosphate carrier. 

I've never used an Accuwedge, but $5 is a lot cheaper than what the heavier buffet and spring cost. The BCG I used today is phosphated. I used it to compare with my nickel boron one. Taking off some anodizing from the CH can't hurt at this point.

[DustinIL]

Latest Update:

Went to the range real quick yesterday to try out an Accuwedge and three other types of magazines (25 rd Pmag GenM3, DPMS, and CPD)...........No change. Charging handle keeps coming back. Even worse, things actually regressed, i.e. I even tried single loads again without a magazine inserted and the charging handle came back. FWIW I was using Austrian milsurp.

I was still using the BCM charging handle. There's still enough of a ledge on the latch side that when I pull on the opposite side (non-ambi) that it won't release. At this point I don't know what the nuts to do besides take it to a gunsmith and see what can be done, if anything.

The kicker is I even emailed the maker of the upper to see if they could give me the inside dimensions of their upper so I could try some measurements...just crickets, and no one answered their damn phone.

So......yeah.