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20-04-2017, 18:13 #31
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20-04-2017, 18:16 #32
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20-04-2017, 19:24 #33
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Re: PMP brass not extracting from DM4
Surely if the bolt requires something as critical as a mere oring for reliable extraction, it would fall under some kind of warranty?
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20-04-2017, 20:19 #34
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Re: PMP brass not extracting from DM4
Perhaps that would explain some of the problems with PMP factory ammo?. Normally a carbine length gas system is fed gas for the 7.5 inches of barrel in front of the gas port (on a 14,5 inch barrel), and then pressure drops off. An 18 inch barrel with a carbine gas system has 11 inches of barrel time providing gas to the system. Paul mentioned over-gassing could be an issue, I am inclined to agree with this possibility.
Normally the gas system on an AR is timed to allow the bolt to start moving back as soon as pressure drops below a certain safe level. The extra 4 inches of barrel on a 18 inch barrel with a 7 inch gas system is going to cause pressure to build up and stay high for a much longer time.
I don't build AR's for a living but I believe Colt, FN, or any of the major manufacturers do not put carbine gas systems on 18 inch or longer barrels, for good reason.
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20-04-2017, 20:21 #35
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- Sep 2013
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If your rifle has an extraction issue due to a rough chamber ,polishing might help,
But if the chamber hasn't been well cut by the factory , re-cutting the chamber with any other 223/5.56 reamer in the same chamber would definitely change the headspace.
One of our club members bought a brand new Ruger AR15 DI rifle.
It failed to extract on all ammo.
Examining the fired cases it revealed a constant protrusion in the brass body. ( bore scope confirmed a faulty chamber. )
In the USA factories would just replace the barrel.
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28-04-2017, 00:10 #36
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- Dec 2013
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- 54
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Re: PMP brass not extracting from DM4
Hey guys. I trust you're well. Just to let you know that I resolved the issue with my DM4 not extracting PMP brass. I fitted the O ring as suggested by SafeAction and it works excellently. A quick cheap fix and I'm waxed. Thanx SafeAction for you help and thank you all for you replies.
God bless
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30-04-2017, 06:47 #37
Re: PMP brass not extracting from DM4
Mozzy any idea what age / date of manufacture the PMP ammunition is?
http://www.gunsite.co.za/forums/show...mp-round-firedQuemadmodum gladius neminem occidit: occidentis telum est.
Seneca (4 BC - 65 AD)
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01-05-2017, 20:45 #38
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Re: PMP brass not extracting from DM4
No idea Wonderin'. There's no indication on the packaging of batch/lot date of manufacture etc.
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30-08-2018, 13:15 #39
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30-08-2018, 14:45 #40
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Re: PMP brass not extracting from DM4
TRG has a valid point. As you mention there are variations between different reamers. All of which alters chamber specs. Then there are potential alignment issues when it comes to cutting and or polishing. Apparently it is not uncommon for cut chambers to not be totally aligned with the bore, more so I would imagine in one off variations. In this regard and especially for machine guns (for info purposes) bore chamber centricity is paramount and hence ideal is hammer forging both at the same time.
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