PMP brass not extracting from DM4

[JRX]

Hi folks. I'm having an issue with my DM4 (.223) not extracting factory PMP brass reliably. I'm using an 18inch semi weight barrel, manufactured by Musgrave, that comes standard with the rifle. The rifle shoots everything else I've tested, with no issues at all, (including my own reloads) except factory PMP .223 Remington, (the brown box). The spent cases stay stuck in the chamber even after the bolt has cycled backwards. This occurs once about every 3-4 rounds. The case extracts like normal, once I've allowed the bolt to shut close again, so it's not sitting unusually tight. I've had the smiths at Diplopoint check it out for me, but there was nothing to fix or replace, because it only has this issue with PMP ammo. Has any other DM4 owner out there experienced similar issues with PMP ammo? I'd really appreciate your input if you've come up with a fix. One fellow shooter suggested that the pressure in the chamber, might still be peaking, while the BCG is cycling rearwards and therefore would not extract the case. Any thought on this?

I've searching online for possible fixes for the exact same problem with the same rifle. Was the only change you made the o-ring?

[driepootx]

PMP FMJ in my 223 gives many pierced primers and I do not shoot them anymore. Speed is at 3340fps in a 24 inch barrel whereas other makes are in the 3140 to 3220fps range. Pressure is thus definitely higher than normal. The timing of extraction might just coincide with higher pressure still present and prevent extraction. I think if you anneal the cases and load to lower speeds you will find no problems.

[FNBROWNING]

Unlikely that PMP is the problem.

[Stevin]

Unlikely that PMP is the problem.

Agreed, PMP is no hotter than Winchester Whitebox 5.56 when I chronied it. Even the Yellowbox Norinco wasn't that much faster than Winchester.

[driepootx]

A check would be to pull the bullets on the PMP and reduce charge by 2gr and shoot again. I would think 10 shots should show up whether there is still a problem.

A quick check on QL suggests that pressure should drop by more than 10K psi for 2gr reduction. Speed down by 200fps.