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Posted: 12/10/2003 7:29:05 PM EDT
I have a 16" DPMS upper with a bull barrel that I purchased used this year and put on my EA lower.  The bolt I am using is out of the EA upper.

The problem is that I can put in 5-20 rounds of 55gr. UMC ammo and it works fine 99% of the time. If I put in Norinco or my reloads it will leave a stuck case in the chamber and the extractor will tear part of the rim off the case 50% of the time. Once in a while it will do this with the UMC ammo.  All of this ammo shoots fine in my VSS Rem 700 and my Eagle with a match upper. My reloads are checked in a case gauge.  I have even tried my Eagle bolt in the EA. Do you think this is a tight chamber issue?  The guy I bought it from said he shot 100 rounds of .223 and 250 round of .22LR. I have cleaned this gun 5 times using Hoppes, Sweets, and MPro7 thinking that I had a dirty bore or chamber.

Any suggestions are appreciated.
Link Posted: 12/10/2003 9:57:51 PM EDT
We've had a lot of reports of tight and/or rough chambers in DPMS barrels. That's what your problem sounds like. Contact DPMS for a return and repair.
Link Posted: 12/11/2003 11:03:36 AM EDT
You say you are using the bolt from your EA in the DPMS barrel. Did you check the headspace?

Tweak, could this be a possible issue?

Link Posted: 12/11/2003 7:38:18 PM EDT
It could be if the HS is short or it could be combination of minus chamber dimensions and short headspace.
Link Posted: 12/12/2003 11:44:49 AM EDT
If it is headspace, can I check it without gauges?
Link Posted: 12/12/2003 1:35:30 PM EDT
You can use a depth mic and ball gauges instead. [;)]
Link Posted: 12/13/2003 10:00:55 AM EDT
I noticed in my old DPMS A2 that softer brass or longer cases tended to get stuck.  SA battlepack would occasionally do this also.  Compare the length of a previously stuck case to an empty of some ammo that does not get stuck.  I think the chamber needs a little more length in the neck area.  Compare em and even when manually chambered the spent cases would do the same.  (short one would pop right out, the longer one would be sticky)
Link Posted: 12/26/2003 8:13:36 PM EDT
Had the same problem on 3 different DPMS 16" bull barreled uppers. Had heard about the DPMS rough chambers so returned them and the problem was not as prevelent but still there intermittionly. The problem is described in Chapter 15 of Derrick Martins book "The complete guide to AR15 accuracy". It is inherent to carbine or short barreled ARs and it is essentially getting to much gas to fast before the case cools for extraction. I sent mine to Derrick at Accurracy Speaks in Arizona and he installed the vented set screw in the gas tube and haven't had a problem since. I also wasted a lot of time and money trying to get acceptable accurracy out the Wilson barrels DPMS uses.  
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