Shortchris1991 Posted April 18, 2020 Report Share Posted April 18, 2020 Hey guys Ive built a few ar15s in the past with no problems and decided to try a lr308 about a year ago and everything seemed to be correct at first, manually cycling the rifle doesn't seem to have any issues to me but at the range I found I have multiple (like nearly every single shot) failures to feed and failures to eject and it also seems to be really rough on the casings compared to my ar15s. I've tried looking for answers online with not much luck (maybe I just missed or overlooked what I needed so I apologise if this has been covered multiple times) but it does seem these builds are riddled with issues and most of them being an incorrect part here and there. So I'm going to start off giving measurements of different parts and hopefully something sticks out to someone. If I miss any vital info please let me know and I will try to get that to you ASAP I really want to get this functioning properly. bcg minus the bolt measures out to just a hair under 8 1/16 inches Buffer Is 2 18/32 inches and weighs about 3.7 oz Buffer spring is about 11 1/2 inches with 28 coils, I have also tried the sprinco extrapower 308 carbine dpms spring which is 11 1/16 Inches with the same 28 coils using the same buffer mentioned above with no success Buffer tube is 7 inches internally I purchased the upper, barrel, gas system already assembled so I don't know much about it other than its an aero precision upper with a 20 inch barrel and I BELIEVE a mid length gas tube (I purchased most of this stuff over a year ago and am a little fuzzy on all the specifics) I finished out a 308 80% lower receiver from Polymer80 (I know alot of people don't like those but I wanted to give it shot after doing a few 80% glocks, and I feel pretty confident that it's within spec but if the experts say that's the only thing that could be wrong I'll just have to swallow my pride and buy a legit lower) To my knowledge everything should be dpms standard and no armalite, from what I've been able to find online most of the issues with these seem to be mixing dpms and armalite parts, and also seems to be a wide range of buffer spring, buffer, buffer tube and possibly bcg(?) combinations that can cause issues. Again if there is any other info needed let me know and I will get you what I can. Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted April 18, 2020 Report Share Posted April 18, 2020 Can you post a picture of the the end of the gas tube looking straight down into the upper? Need to see the location in relation to the cam pin cut out in the receiver. Does it lock back after firing with one round? Is the catch is on the bolt face and not the carrier? Quote Link to comment Share on other sites More sharing options...
Shortchris1991 Posted April 18, 2020 Author Report Share Posted April 18, 2020 Yes it was locking back, but im not sure what it was catching on. I do believe my buffer is getting beat up by the retaining pin though. Quote Link to comment Share on other sites More sharing options...
shooterrex Posted April 18, 2020 Report Share Posted April 18, 2020 Your gas tube is way to short. It should come to the middle of the cam pin cutout. Quote Link to comment Share on other sites More sharing options...
Shortchris1991 Posted April 18, 2020 Author Report Share Posted April 18, 2020 Is there anything I can do to fix this? 5 minutes ago, shooterrex said: Your gas tube is way to short. It should come to the middle of the cam pin cutout. Quote Link to comment Share on other sites More sharing options...
shooterrex Posted April 18, 2020 Report Share Posted April 18, 2020 Just now, Shortchris1991 said: Is there anything I can do to fix this? Armalite carbine 308 gas tube should be a fix. White oak armament makes custom length gas tubes. Pull that one and measure it. Also your buffer with the 7" buffer tube should be 2.5" and weigh about 5.6 oz. But fix 1 thing at a time. Quote Link to comment Share on other sites More sharing options...
Shortchris1991 Posted April 18, 2020 Author Report Share Posted April 18, 2020 Awesome, thank you! Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted April 18, 2020 Report Share Posted April 18, 2020 Looks like your buffer could be hitting the buffer detent during cycling. Could be a slightly out of "spec" lower. An offset detent would solve that, maybe. https://gallowayprecision.com/offset-buffer-retainer-for-AR-15-rifles Might be something else out of whack, does the carrier push the buffer back a touch as you close up the receivers? Quote Link to comment Share on other sites More sharing options...
Shortchris1991 Posted April 18, 2020 Author Report Share Posted April 18, 2020 2 minutes ago, jtallen83 said: Looks like your buffer could be hitting the buffer detent during cycling. Could be a slightly out of "spec" lower. An offset detent would solve that, maybe. https://gallowayprecision.com/offset-buffer-retainer-for-AR-15-rifles Might be something else out of whack, does the carrier push the buffer back a touch as you close up the receivers? I will try that offset retainer too. It doesnt appear that the carrier is pushing the buffer back but it looks super close I think an offset retainer might let it out just enough, I didn't even know anyone made those, thank you. Quote Link to comment Share on other sites More sharing options...
Shortchris1991 Posted April 30, 2020 Author Report Share Posted April 30, 2020 OK so I am working on a few projects right now and have not bought the offset detent or heavier buffer yet but I will soon, I did get the 308 gas tube and installed it but then the tube was bottoming out in the gas key and not allowing the bolt to close all the way, the gas port was set back exactly where it was before I marked it before taking the old gas tube out. I lightly polished the end of the gas tube and now the bolt closes just fine, do yall think this will be ok/safe to try and fire it after I get the buffer and offset detent? Quote Link to comment Share on other sites More sharing options...
Shortchris1991 Posted April 30, 2020 Author Report Share Posted April 30, 2020 Gas *block* was set exactly where it was before, sorry I'm tired just got off work Quote Link to comment Share on other sites More sharing options...
shooterrex Posted May 1, 2020 Report Share Posted May 1, 2020 Looks good to me. Quote Link to comment Share on other sites More sharing options...
Shortchris1991 Posted May 1, 2020 Author Report Share Posted May 1, 2020 Thank you sir. Have you heard of people having to sand or polish the end to the gas tube to seat in the key properly? I've never had that issue with ar15s but I guess 308 parts are kinda all over the place spec wise I just hope I don't get gas leaking out and losing pressure still. Also I was thinking and reading more on other peoples problems with these rifles and I've seen a few people say that their gas tube was like my previous one and the rifle worked fine, is it possible that it could have been only a recoil issue due to my light buffer, or is there likely another factor that made theirs more reliable even with the shorter tube? I'm still going to get the heavier buffer just in case, probably will be awhile until I can take it out to test anyhow. Just thinking, trying to soak up as much info as possible. Man I wish they would just get specs set on these like the ar15, seems alot of people right from the get go are reluctant to try what I believe could be a great rifle all because of completely avoidable problems, if manufacturers would just work together instead trying to go down their own road. Thank you all for your help, hopefully I'm on the road to a fully functional rifle. I will definitely keep yall posted on results. Side note I was rereading my original post and I may have fudged up one detail, the failure to feed properly happened nearly every shot I would either get a round jammed mid feed or no feed at all just a closed bolt with no round in the chamber, failures to eject were much less common, idk if that changes things. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted May 1, 2020 Report Share Posted May 1, 2020 2 hours ago, Shortchris1991 said: Side note I was rereading my original post and I may have fudged up one detail, the failure to feed properly happened nearly every shot I would either get a round jammed mid feed or no feed at all just a closed bolt with no round in the chamber, failures to eject were much less common, idk if that changes things. Go back over the numbers on your recoil system again. On 4/18/2020 at 12:17 PM, Shortchris1991 said: bcg minus the bolt measures out to just a hair under 8 1/16 inches Buffer Is 2 18/32 inches and weighs about 3.7 oz That buffer is long-ish, should be 2.500" and no longer, and it's light. It should be 5.4oz or damn close, to run the Spring Orange spring. You didn't state the exact Sprinco spring that you used - they code them by color. What was the color code on the Sprinco spring that you used - should have been the Orange spring... Buffer spring is about 11 1/2 inches with 28 coils, I have also tried the sprinco extrapower 308 carbine dpms spring which is 11 1/16 Inches with the same 28 coils using the same buffer mentioned above with no success Buffer tube is 7 inches internally Plus, your gas tube was WAY short. You solved that part. Look at your recoil system parts again, re-measure. Check it all over again. The buffer is definitely light, and needs to be heavier. What you had to start with was one hell of a "compromise-system" that didn't get it right. Short gas tube, light buffer that's a tad too long, whatever-spring... Next up is your gas port diameter. Have you measured it? Solve what you can solve first, fix what needs to be fixed. Quote Link to comment Share on other sites More sharing options...
Shortchris1991 Posted May 1, 2020 Author Report Share Posted May 1, 2020 37 minutes ago, 98Z5V said: Go back over the numbers on your recoil system again. Plus, your gas tube was WAY short. You solved that part. Look at your recoil system parts again, re-measure. Check it all over again. The buffer is definitely light, and needs to be heavier. What you had to start with was one hell of a "compromise-system" that didn't get it right. Short gas tube, light buffer that's a tad too long, whatever-spring... Next up is your gas port diameter. Have you measured it? Solve what you can solve first, fix what needs to be fixed. I will check number again tomorrow after work I'm about to hit the sack, I'm sure my measurements aren't the best, I'll see what I can do about getting a gas port measurement, I have the orange sprinco, I'm going to get the a heavier buffer I don't remember which one I was looking at but it was like 5.4 or 5.6oz. I tried to get most of it in sets, complete upper, and the recoil stuff other than the sprinco all came together "for lr308" I guess that's what I get for not doing more research beforehand. Thank you for your time and wisdom. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted May 1, 2020 Report Share Posted May 1, 2020 I'm here for this project, man, all the way through it - fully invested. This gun will run. It's mechanical, so it can't out-think us. It will be beaten. Quote Link to comment Share on other sites More sharing options...
thossoma@pm.me Posted August 23, 2021 Report Share Posted August 23, 2021 Wondering if this got solved. I'm having a similar issue where my bolt won't lock back after firing the last round from a mag, also it will eject the round only 5% of the time. If I cycle the bolt manually, it will eject and feed with no problems and lock back the bolt on the last round without issue. Quote Link to comment Share on other sites More sharing options...
thossoma@pm.me Posted August 23, 2021 Report Share Posted August 23, 2021 Here is some pictures Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted August 23, 2021 Report Share Posted August 23, 2021 14 minutes ago, thossoma@pm.me said: Wondering if this got solved. I'm having a similar issue where my bolt won't lock back after firing the last round from a mag, also it will eject the round only 5% of the time. If I cycle the bolt manually, it will eject and feed with no problems and lock back the bolt on the last round without issue. I will recommend that you start a thread dedicated to your rifle. It makes sure that we are only talking about your rifle. There will be questions about your rifle and its configuration. Please read this thread to see what kind of info will be asked. https://forum.308ar.com/topic/19170-waterboarding/?tab=comments#comment-302006 Quote Link to comment Share on other sites More sharing options...
thossoma@pm.me Posted August 23, 2021 Report Share Posted August 23, 2021 On it! Thanks! Quote Link to comment Share on other sites More sharing options...
98Z5V Posted August 23, 2021 Report Share Posted August 23, 2021 1 hour ago, Armed Eye Doc said: I will recommend that you start a thread dedicated to your rifle. It makes sure that we are only talking about your rifle. There will be questions about your rifle and its configuration. Please read this thread to see what kind of info will be asked. https://forum.308ar.com/topic/19170-waterboarding/?tab=comments#comment-302006 He didn't read it, Doc... Not before starting that new thread. If read, not understood. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.