Ranger58SN Posted October 2, 2012 Report Share Posted October 2, 2012 Hi guys,I'm brand new to the forum so if I do something stupid please forgive me. I just recently built a JD 308 with dpms bolt, buffer, spring, and SASS barrel. I took it out to break it in with a couple of 20lr pmags but it FTF about every other round and after searching around I read the pmags were a no-go for the JD. Mine was showing extreme wobbling and would work by holding the mags like others, I was disappointed but I decided to try a dpms mag. It did the exact same thing, so I took out the calipers and measured the magwell of mine as well as another that was ordered at the same time, both measured out at 2.965. So my question is, before I send it back to JD: are these receivers that out of spec or am I having a buffer/timing problem? Any measurements of properly functioning dpms magwells would be helpful to me to properly troubleshoot this issue!Thanks Drew L. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted October 2, 2012 Report Share Posted October 2, 2012 I'll bring home the calipers tomorrow and measure my DPMS receiver. <thumbsup> Quote Link to comment Share on other sites More sharing options...
NoFail Posted October 2, 2012 Report Share Posted October 2, 2012 My JD magwell measures out to 2.9630. For your reference I took measurement from the top of magwell, not the bottom where mag inserts into. It's difficult to get accurate reading from bottom of well. And I had the calipers slid all the way to to side wall. Both sides are pretty equal. I use Pmags exclusively and they have been error free in my JD lower. Quote Link to comment Share on other sites More sharing options...
Robocop1051 Posted October 2, 2012 Report Share Posted October 2, 2012 The way I understand it, JD has an unofficial gen1 and gen2 lower receiver. They changed their process about 12-18 months ago. I heard rumor that JD used CMMG magazines on their first lowers. They assumed all magazines were the same. I'll reserve my opinion of CMMG for the sake of those who own their products. You have a few options.1. Contact JD and see if they have a remedy. 2. T&E more magazines till you find one that works. 3. Try to shim the magwell to accept the PMAG. 4. Do what I did.... Sell it... Then buy a MA-10! Or an AR10A!! Quote Link to comment Share on other sites More sharing options...
Ranger58SN Posted October 2, 2012 Author Report Share Posted October 2, 2012 Thanks for all the responses! Currently my plan of action is:try another buffer then send it back to jd, they said that if dpms mags didn't work then to send themthese are brand new receivers that they just got in a couple of months ago so I just want to make sure that buffer isn't the issue before I do send it. The mags have a pretty good wobble but I wouldn't think that could be the only reason. You guys with properly functioning JDs with pmags, do yall have a significant wobble? How's the fit? Quote Link to comment Share on other sites More sharing options...
NoFail Posted October 2, 2012 Report Share Posted October 2, 2012 At bottom of LR-20 Pmag it rocks back & forth a good 1/8" maybe 3/16" in my JD lower. Quote Link to comment Share on other sites More sharing options...
Dusty44 Posted October 2, 2012 Report Share Posted October 2, 2012 My DPMS LR-308, factory rifle, vintage spring 2010, magwell measures 2.955 on the bottom and maybe 2.947+ on the top. I also got 2.953 and some other measurements in that ballpark on the top. Things keep moving.PMags and factory steel mags fit with just enough clearances for easy extraction; lock solidly in place. What little wiggle there is seems to be a pivot around the retaining lug. This is with the upper and lower separated.With the rifle assembled and an empty PMag inserted, pushing against the mag, the spring tension in the mag pressing against the follower can be felt as the mag body moves relative to the follower which is pressed against the BCG. Movement is very slight. Quote Link to comment Share on other sites More sharing options...
unforgiven Posted October 3, 2012 Report Share Posted October 3, 2012 Welcome frome Idiana brother Ranger58SN,You came to the right place.Lost's of sharp guys. <thumbsup> Quote Link to comment Share on other sites More sharing options...
Ranger58SN Posted October 4, 2012 Author Report Share Posted October 4, 2012 Hey Guys,Thanks for all the help and warm welcomes. I have tried a different buffer and some higher quality ammo and it seems to be running perfectly so far. Let's hope it keeps up! Quote Link to comment Share on other sites More sharing options...
NoFail Posted October 4, 2012 Report Share Posted October 4, 2012 Ranger, that's great news, good for you! Which buffer? Yeah, I never shot cheap ammo in mine, but they say it can be a bad thing. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted October 6, 2012 Report Share Posted October 6, 2012 Hey Guys,Thanks for all the help and warm welcomes. I have tried a different buffer and some higher quality ammo and it seems to be running perfectly so far. Let's hope it keeps up!Run her wet with good lube for the break in period & don't forget the buffer & spring . I also use a little grease on the backs of the bolt locking lugs & cam pin .Sounds like the action was short stroking , what that does is ,instead of the bolt face striping the cartridge from the mag, the bolt carrier tries to & thats a bad angle & the bolt also is above the cartridge , then it gets ugly ,can leave some good dents . Yes, what buffer did you go with , interesting , that just the buffer solved this issue , seems there should be more to it , unless the wrong buffer was in there to begin with ? Quote Link to comment Share on other sites More sharing options...
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