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Posted: 4/21/2012 11:58:05 PM EDT
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I just bought a DPMS stripped lower and used a daniel defense lower parts kit to complete it. I then fit a DPMS m4 upper to it and when i cycled the bolt everything was ok Then showing it to a buddy the bolt jamed going forward into battery. Turns out That DPMS may have bored the retainer hole too close to the hammer well. The separaton between the two or web that is left is only a hair thick. I never saw anything like this on my other receivers (bushmaster) My buffer retainer pin got pretty worked in the process so i replaced it along with a new spring which also got wasted.
Here is where things get really frustrating. Since the hole appears to be set forward (im no expert ) in order for the buffer tube to properly retain the pin in the hole, it actually interferes with proper mating of the upper & lower beacuse it protrudes just a bit too far into the lower interfering with lockup or mating of the upper/lower If I back out the tube a full turn so my Magpul butstock indexes properly. The retainer pin appears to be held down. That is untill you cycle the bolt, the retainer squirts out and the whole mess starts over again. The wall or web thats left between the hole and the lower looks way too thin. and it looks like it may even fail I did not cause this condition. But I didnt catch it when I bought the lower. If I tried to have a gunsmith build up the wall of the retainer hole and re bore it, im thinking it likley would cost more than the price of a new lower. And of course since we are talking about the registered part of the weapon. Exchange seems way complicated. Especially here in Kalifonia 
Does DPMS have a moderator here? Has anybody seen this type of problem? I even thought of letting the buffer tube extend in to retain the pin at the bottom, and file the rest to allow for a flush fit that would not interfere with the upper/lower but that still leaves that really thin wall that looks scary. I would appreciate any help on this Thanks Grjrecon |
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The retainer pin hole needs to be forward to allow the carrier to push the buffer off the pin when you close the upper.
The problem of having to screw the stock tube so far to retain the pin that it interfered with the upper closing is not too unusual. Used to happen more often when stock tubes were cut straight on the end and did not have the protrusion at the bottom to catch the buffer detent. I used to correct the problem by filing the tube down and leaving a lip at the bottom like new style tubes have or ordering a new tube from someone. If you try relocating the detent hole rearward there is a chance you will get the buffer battering into the detent when the gun cycles. I always adjust the cheapest part which is the stock tube. |
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Try contacting DPMS. I'm sure they will exchange it for you if it is out of spec. You can also run without the retainer, it isn't needed for operation, you will just need to take the upper off using both takedown pins instead of pivoting it open on the front pin. |
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Quoted:
I just bought a DPMS stripped lower and used a daniel defense lower parts kit to complete it. I then fit a DPMS m4 upper to it and when i cycled the bolt everything was ok Then showing it to a buddy the bolt jamed going forward into battery. Turns out That DPMS may have bored the retainer hole too close to the hammer well. The separaton between the two or web that is left is only a hair thick. I never saw anything like this on my other receivers (bushmaster) My buffer retainer pin got pretty worked in the process so i replaced it along with a new spring which also got wasted. Here is where things get really frustrating. Since the hole appears to be set forward (im no expert ) in order for the buffer tube to properly retain the pin in the hole, it actually interferes with proper mating of the upper & lower beacuse it protrudes just a bit too far into the lower interfering with lockup or mating of the upper/lower If I back out the tube a full turn so my Magpul butstock indexes properly. The retainer pin appears to be held down. That is untill you cycle the bolt, the retainer squirts out and the whole mess starts over again. The wall or web thats left between the hole and the lower looks way too thin. and it looks like it may even fail I did not cause this condition. But I didnt catch it when I bought the lower. If I tried to have a gunsmith build up the wall of the retainer hole and re bore it, im thinking it likley would cost more than the price of a new lower. And of course since we are talking about the registered part of the weapon. Exchange seems way complicated. Especially here in Kalifonia
Does DPMS have a moderator here? Has anybody seen this type of problem? I even thought of letting the buffer tube extend in to retain the pin at the bottom, and file the rest to allow for a flush fit that would not interfere with the upper/lower but that still leaves that really thin wall that looks scary. I would appreciate any help on this Thanks Grjrecon 1. Whoever mills DPMS' lower receiver forgings is cutting the FCG void space 1.5mm further back than other lowers - this comparing my DPMS to my Spike's lower. Retainer pin holes are located same. Shouldn't be a problem, as there's no side load on the pin during operation. 2. I've had the exact problem you describe, and determined the true cause to be a dimensionally-incorrect receiver extension tube. Replaced it with a name brand, problem over. Hope this is helpful. GMS . |
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