boostless Posted January 18, 2015 Report Share Posted January 18, 2015 I posted this in my "build thread" but want to bring it out to clear some things up. My bolt will not go back far enough to have the bolt catch engage the face of the bolt. The rifle will fire and cycle with out a problem it just won't lock open on an empty mag. Test firing was with a 20 round magpul mag loaded with 5 rds. Parts are as follows: Aero upper/lower set Aero BCG DPMS stock set: http://www.buckeyetactical.com/dpms-buttstock-assembly-6-position-collapsible-lr-308-ar-15-carbine-synthetic-black.html Magpul mags Charging handle is just a standard one: http://www.surplusammo.com/ar-10-lr-308-charging-handle-complete/ The measurements on the buffer stuff: Spring measures 10.5 inches just sitting on the table and has 38 coils Buffer measures 2.5 inches including the rubber end piece Tube depth is 7 inches Any help would be appreciated since the buffer system is what really confuses me on these rifle systems. Quote Link to comment Share on other sites More sharing options...
edgecrusher Posted January 18, 2015 Report Share Posted January 18, 2015 I don't think it's your buffer. It sounds like the right one, at least part wise. The only thing there (and I'm not sure it's your issue) is maybe a heavier buffer to slow the cyclic rate (will also greatly reduce recoil). What parts kit did you use when building? Wondering what bolt catch you used. Armalite makes the best one for this platform, by far it's beefier than others, but may need to be fitted. Also, and maybe most telling and cheapest, what's the round count and what was your lube situation? The larger frame rifle can take up to and/or over a couple hundred rounds to break in, preferably running sloppy wet. Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 round count is at 10. LPK was a CMMG. I'm not gonna jump into the AR-10 bolt catch yet. The bolt has another half inch to move back before it's even capable of being engaged by the bolt catch when pulled back with the charging handle. It cycles just fine when firing the only problem I had with the cycling is getting the first round chambered after that it runs fine. I would say that the bolt was pretty wet, I had oil seeping out between the receivers. Quote Link to comment Share on other sites More sharing options...
edgecrusher Posted January 18, 2015 Report Share Posted January 18, 2015 round count is at 10. LPK was a CMMG. I'd start here. Too low of a round count and CMMG bolt catch is a known issue. I'll let others chime in, but.... Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 I'll wait to hear from others because I don't think it's gonna break in to allow the bolt to move back another half inch and the bolt catch will lock the BCG back on the carrier body. Quote Link to comment Share on other sites More sharing options...
Zebra644 Posted January 18, 2015 Report Share Posted January 18, 2015 (edited) Did you try another P-mag to ensure that it by some chance was a bad one? If you are running a DPMS carbine length tube are you you running a carbine length 308 buffer and spring? If all the answers to this is yes, than its the CMMG Bolt catch. Easy and cheap fix. Edited January 18, 2015 by Zebra644 Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 If you can't give me a reason that it's the bolt catch then please don't mention it. It is not causing the bolt to stop it's rearward travel. Yes, I have tried multiple pmags. I ordered a 308 buffer tube kit so all the parts should be for a 308 and I gave what measurements I have. The bolt does not travel far back enough to get to the point where the bolt catch can even engage the bolt face. Quote Link to comment Share on other sites More sharing options...
guruofhotrod Posted January 18, 2015 Report Share Posted January 18, 2015 (edited) I'd have to check but, if it's not the CMMG catch (CMMG stuff has a questionable reputation around here) it might be the action spring it is possible you may have received an AR15 spring by mistake - that spring would reach coil bind and could cause the problem you are experiencing, I'll try to find a minute to check the # of coils on one of my DPMS carbine length springs and report back later. Edited January 18, 2015 by guruofhotrod Quote Link to comment Share on other sites More sharing options...
98Z5V Posted January 18, 2015 Report Share Posted January 18, 2015 Wrong spring? You running a rifle spring? Measure the relaxed length of the spring. Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 Thank you Guru, I know it's not a great brand which is why I'm annoyed that's what everyone keeps pointing to. 98, how do I relax the spring? When I got that measurement the spring was just sitting on the table. Quote Link to comment Share on other sites More sharing options...
Matt.Cross Posted January 18, 2015 Report Share Posted January 18, 2015 98, how do I relax the spring? When I got that measurement the spring was just sitting on the table. By relaxed he just means uncompressed, if you measured it that way you have the relaxed measurement. CMMG is rightly another four-letter word around here, their products are preferred by Satan worshipers and sadists everywhere. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted January 18, 2015 Report Share Posted January 18, 2015 That measurement you gave in the first post - 10.5". That's about 3" too short, and 4 coils too many. That's why I asked. Sitting it on the table is the relaxed length - not compressed. Wrong spring for a .308 AR, for certain. Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 Okay, I thought that was the relaxed measurement but when you said to get the relaxed measurement I wasn't 100% sure. The buffer is good to go right? at least with the length? Quote Link to comment Share on other sites More sharing options...
98Z5V Posted January 18, 2015 Report Share Posted January 18, 2015 (edited) The buffer is good to go right? at least with the length? Yes, 2.5" buffer for a 7" internal depth carbine receiver extension. I think you're hitting coil bind on that weirdass spring - whatever that thing is meant for. It doesn't match any .308 AR or AR-15 published lengths or coil count, at all. EDIT - That might be a spring for some RRA .308 Carbine design - have to hit up the RRA owners. Edited January 18, 2015 by 98Z5V Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 I'll wait to hear back from guru with the info on his spring before I start looking into new springs as I'm a little tapped out on money right now. Quote Link to comment Share on other sites More sharing options...
shibiwan Posted January 18, 2015 Report Share Posted January 18, 2015 (edited) Can you lock the bolt if you pull it all the way back by hand? Does it catch on the bolt face? Edited January 18, 2015 by shibiwan Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 There is nothing I can do to get the bolt back far enough to have the bolt catch engage the bolt face with the buffer and spring installed. I can get it to lock back with the bolt catch on the carrier body, where the bolt inserts, but not on the bolt face. Quote Link to comment Share on other sites More sharing options...
shibiwan Posted January 18, 2015 Report Share Posted January 18, 2015 Likely spring bind. To confirm put a small dot of grease on the rubber end of the buffer, carefully reassamble without messing up the dot of grease. Pull the thing all the way back, and release, then disassemble and inspect. If the rubber tip hit the end of the buffer tube, the grease dot will end up being smeared. If the spring is binding on the coils, the rubber tip won't make it to the back of the tube and the dot will be somewhat intact. Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 I'll give that a check when I get back home, gotta go pick up the wife from the airport. Quote Link to comment Share on other sites More sharing options...
shibiwan Posted January 18, 2015 Report Share Posted January 18, 2015 (edited) Screw that. Let her find her own way back. <lmao> <laughs> Edited January 18, 2015 by shibiwan Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 So it's not going all the way back. I had my wife stick an allen wrench in the little hole on the buffer tube and it went in about 1 3/8 in. so I think with the thickness of the end of the buffer tube it still has about 1/2 to 3/4 of an inch to compress. I didn't have actual grease but I used some engine assembly lube to test and it wasn't compressed/squished/spread out at all. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted January 18, 2015 Report Share Posted January 18, 2015 Action spring coil bind. $hitcan that spring. Quote Link to comment Share on other sites More sharing options...
boostless Posted January 18, 2015 Author Report Share Posted January 18, 2015 any recommendations as I start looking around? Quote Link to comment Share on other sites More sharing options...
FaRKle! Posted January 18, 2015 Report Share Posted January 18, 2015 any recommendations as I start looking around? Heavy Buffers' LR-308 carbine action spring (modified AR-10 spring) is about the best spring you can get. If you do purchase through Brownell's, please use our affiliate link! Quote Link to comment Share on other sites More sharing options...
survivalshop Posted January 19, 2015 Report Share Posted January 19, 2015 This is my DPMS Carbine spring & the long one is a Superior Spring ( Tubb's ) I think you have the wrong spring also, count the coils & look at the length . Quote Link to comment Share on other sites More sharing options...
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