Vwporschegt3 Posted March 6, 2020 Report Share Posted March 6, 2020 First off I just have to say there is such a great wealth of knowledge here and I appreciate everything that's been posted in here. Dad bought this upper and I have spent the last year dicking with it trying to make it right. Having done some aggressive research I came across the gas tube length and have determined, among some others , what the problem seems to be with this gun... and I believe it directly kings to the length of the gas tube. Currently the tube does not project into the cutout with for the bolt retainer , so an armalite gas tube will be on order.... secondly the gas port on the 20" barrel was only .069".... port was opened to .095" by me and it started cycling to what I would say is 80% of the time. I'm a reloader and have been shooting my own reloads as well as about 2 boxes worth of winchester through it. Same results . My loads are 25.5grns of 4320 with sierra 150gr. Bullets. These are all hand metered loads so I know they are extremely consistent. This was a "budget build" so the recoil system is what came out of the utg ar308 a2 stock box. I have been reading that I may need to adjust the buffer weight to 5.4ounces? And what spring would be ideal? The rest of the lower is dpms parts on a 80% lower. I have a second lower configured exactly the same and get the same issues across the board. Any and all advice is welcome. I understand from the get go this is a hodgepodge . Thanks guys Quote Link to comment Share on other sites More sharing options...
Vwporschegt3 Posted March 6, 2020 Author Report Share Posted March 6, 2020 Btw the issue is short stroking Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted March 6, 2020 Report Share Posted March 6, 2020 Can you give a parts list of what you have in the rifle? Please be as specific as possible. A picture of the gas tube and where it ends would be helpful as well. Can you weigh your buffer, measure your spring and measure the inside depth of you buffer tube? I am not the best at diagnosing these, but this info would be helpful for those who are. Quote Link to comment Share on other sites More sharing options...
Vwporschegt3 Posted March 6, 2020 Author Report Share Posted March 6, 2020 Will do I'll get the info in a few hours Quote Link to comment Share on other sites More sharing options...
Vwporschegt3 Posted March 7, 2020 Author Report Share Posted March 7, 2020 (edited) Here is the gas tube. I dont have a scale to weigh the buffer. But again this is a thunderguns.com upper 20". I'm going to replace the gas block with an adjustable and the gas tube with the armalite that is .325" longer. The stock on my lower is the leapers utg ar308 stock it came with the "308" spring and buffer The lower is a gen 1 dpms pattern 80 percent with dpms lower parts kit. I'm using magpul sr25 20 round mags , I dont think I'm having a mag problem since the problem seems to be with short stroking. I also modified the ejector since it was the flat type, I rounded the edges and have yet to test it. I will weigh the buffer on monday and will be able to tell you the weight then Edited March 7, 2020 by Vwporschegt3 Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted March 7, 2020 Report Share Posted March 7, 2020 Your gas tube is extremely short. It should extend to the middle of the cutout. I think you are on the right track by replacing it. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted March 7, 2020 Report Share Posted March 7, 2020 Read this thread, and look at the detail on parts that this guy posted, and look at the responses he got - this is the level of detail needed here, in order to figure out what's REALLY going on with your gun. Quote Link to comment Share on other sites More sharing options...
Vwporschegt3 Posted April 18, 2020 Author Report Share Posted April 18, 2020 Just to round this one out.. armalite tube and adjustable gas block brought this gun in to harmony... after tuning the block it cycles a locks open on last round with just about anything I can throw in it.. it has become extremely reliable . If anyone ever buys a thunderguns 20" rifle.length gas upper and decides to run a utg 308a2 stock... check your gas port size for one, the buy a gas tube and adjustable block... this is just as reliable as any ar15 I've owned now Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted April 18, 2020 Report Share Posted April 18, 2020 13 minutes ago, Vwporschegt3 said: Just to round this one out.. armalite tube and adjustable gas block brought this gun in to harmony... after tuning the block it cycles a locks open on last round with just about anything I can throw in it.. it has become extremely reliable . If anyone ever buys a thunderguns 20" rifle.length gas upper and decides to run a utg 308a2 stock... check your gas port size for one, the buy a gas tube and adjustable block... this is just as reliable as any ar15 I've owned now Great to hear that. 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.