TheFinalGeneration Posted April 30, 2013 Report Share Posted April 30, 2013 hey guys, Ive put about 350 rnds through my DPMS MK12 without a malfunction of any kind. The rifle shoots MOA and appears to operate flawlessly. But after shooting the other day i noticed this so maybe the receiver extension is too long? buffer too short? BCG too short? is this worth sending it back to DPMS to have them look at it? Also, what could this type of damage do to the life span of the lower receiver? I assume (provided the problem is corrected) the damage is purely cosmetic and wont effect the operation of the rifle. Is that correct? Let me know what you guys think Quote Link to comment Share on other sites More sharing options...
EasyEJL Posted April 30, 2013 Report Share Posted April 30, 2013 are there marks on the bcg too? Quote Link to comment Share on other sites More sharing options...
TheFinalGeneration Posted April 30, 2013 Author Report Share Posted April 30, 2013 Yea, its not deformed, it just has some extra wear at the bottom corners where the carrier increases diameter Quote Link to comment Share on other sites More sharing options...
survivalshop Posted May 1, 2013 Report Share Posted May 1, 2013 Sounds like you have excessive BCG travel. Wrong spring or buffer ? Pull the spring & buffer , weigh the buffer & count the coils of the spring. Looks like a rifle receiver extension , is that what stock you have on the rifle ? Quote Link to comment Share on other sites More sharing options...
98Z5V Posted May 2, 2013 Report Share Posted May 2, 2013 ^^^ Definitely the first things to look at. When you can, get the details of those two inspections in here. Buffer info, spring info, receiver extension info. Quote Link to comment Share on other sites More sharing options...
StainTrain Posted May 3, 2013 Report Share Posted May 3, 2013 (edited) Had the same problem with my TM-10 and a PSA 6 position receiver extension. I measured how much over travel and a removed the excess material from the thread end until the BCG no longer bottomed out. There should a little extra meat on the extension before you get to the threads. Since discovering the marks and fixing it, I have sent a lot of bullet to their death with no issues. Edited May 3, 2013 by StainTrain Quote Link to comment Share on other sites More sharing options...
TheFinalGeneration Posted May 7, 2013 Author Report Share Posted May 7, 2013 Hey guys, here are several pictures showing the length of various parts of the rifle. It is a completely stock MK12 308 dressed the same way it was the day i completed the transfer, if that helps anyone. Ive been wondering if this problem could have started recently because the receiver gouges don't look like 350 rounds worth damage, is it possible that this due to over-pressured ammunition? On the other hand, this.. ...makes me wonder if the receiver extension is 1 rotation shy of being in the correct position, it looks like i might be able to get the extension a little closer to the buffer retainer, but i don't know. Opinions? survivalshop- honestly i don't know if the RE is rifle length or not, it came with the B5 SOPMOD stock on a 6 position tube. Here is a pic showing the tubes length. I am not at all familiar with the correct dimensions of these items, if anyone notices anything out of spec please lemme know. Quote Link to comment Share on other sites More sharing options...
StainTrain Posted May 7, 2013 Report Share Posted May 7, 2013 (edited) If you are handy with a bastard file, you can repair this jewel in under 20 mins. There is some excess metal (almost like a lip) at the bottom of the receiver extension that contacts the detent. You can take that off and it will give you a turn or two. That is all you need. If you still need help, pm me and we can set up some visuals over Skype or YouTube or email or something. Edited May 7, 2013 by StainTrain Quote Link to comment Share on other sites More sharing options...
stdriver Posted May 7, 2013 Report Share Posted May 7, 2013 (edited) TFG can you show the contact points on the bcg that you think are hitting the lower extension tower. I see wear on the threads of the tower, but no damage to the buffer tube that is visible in the picture. If the corners of the bcg are working on the threads of the tower you can grind down the threads as they are not being used or as a last resort you can radius the corners of the bcg to eliminate the wear on the threads.,. just giving options stdriver Edited May 7, 2013 by stdriver Quote Link to comment Share on other sites More sharing options...
unforgiven Posted May 7, 2013 Report Share Posted May 7, 2013 Welcome from Indiana brother stdriver.Is it the white marks on the extention tube you are refering to?? <dontknow> Quote Link to comment Share on other sites More sharing options...
EasyEJL Posted May 7, 2013 Report Share Posted May 7, 2013 It is a completely stock MK12 308 dressed the same way it was the day i completed the transfer, if that helps anyone. survivalshop- honestly i don't know if the RE is rifle length or not, it came with the B5 SOPMOD stock on a 6 position tube. Here is a pic showing the tubes length. Ok, just wondering, how its a stock MK12, and has a replaced tube + stock? Is the buffer spring + buffer the ones that came with the rifle or came with the SOPMOD? Quote Link to comment Share on other sites More sharing options...
TheFinalGeneration Posted May 7, 2013 Author Report Share Posted May 7, 2013 Thanks stdriver and staintrain, I agree that will solve the problem, but I'm still left wondering which part is out of spec. I guess if it functions reliably, it doesn't really matter but I'd still like to know. Easy- the current line of DPMS MK12 308s come with the SOPMOD from the factory http://www.dpmsinc.com/308-MK-12_ep_96-1.html I think I have seen them with the A2 tho. The tube/buffer/spring are all original. Quote Link to comment Share on other sites More sharing options...
EasyEJL Posted May 7, 2013 Report Share Posted May 7, 2013 Ah ok, just the way you worded it sounded like you replaced the original with the sopmod. Thats a pretty nice factory setup. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted May 8, 2013 Report Share Posted May 8, 2013 The wear you show is not normal, some thing is going on . At no time should your BC contact the threads of the receiver or its extension. The receiver extension is a guide for the BCG. I see there is a collapsable stock configuration. If its factory stock rifle , I would think an AR 10 buffer spring & one of Slash's buffers would stop the excessive BCG travel, but as said before ,measure the length of the spring & how many coils it has ? Also weigh the buffer. Also check for alignment issues , are the pivot & disassembly pins tight & how much play between the upper & lower ? Quote Link to comment Share on other sites More sharing options...
StainTrain Posted May 8, 2013 Report Share Posted May 8, 2013 Thanks stdriver and staintrain, I agree that will solve the problem, but I'm still left wondering which part is out of spec. I guess if it functions reliably, it doesn't really matter but I'd still like to know. Easy- the current line of DPMS MK12 308s come with the SOPMOD from the factoryhttp://www.dpmsinc.com/308-MK-12_ep_96-1.html I think I have seen them with the A2 tho. The tube/buffer/spring are all original. Out of spec??? Brother, you are in 308 country now. There ain't no "in spec." More like in the neighborhood. :-) Knowing what the rifle is supposed to do, what it is doing, what it ain't doing, will help you get your rifle in its own proper spec. I have seen your dilemma about a half a dozen times and experienced once for myself. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted May 8, 2013 Report Share Posted May 8, 2013 (edited) First, that's no rifle receiver extension, at all. It's a carbine extension, and it's not an Armalite .308 AR-10 carbine extension - those have an internal depth of 7 5/8", and they run buffers that are the exact same length as a carbine buffer from an AR15 - hence, the different internal depth. AR15 carbine receiver extensions are standard, at 7" internal depth. We run those, most of the time, on DPMS-based .308 ARs, with short buffers - which you have, at 2.5" long. You have the right buffer. You appear to have the right receiver extension - but you need to measure it's internal depth to be certain. You can save some time on the cutting of threads or filing the end of the extension, by making that measurement first. That way, you'll know what the problem is, and how much you need to take of. <thumbsup> EDIT - If my math works right, your buffer might be 1/8" too short... Edited May 8, 2013 by 98Z5V Quote Link to comment Share on other sites More sharing options...
survivalshop Posted May 9, 2013 Report Share Posted May 9, 2013 Another option would be to get a Superior springs ( Tubb's ), buffer spring. Quote Link to comment Share on other sites More sharing options...
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