teedge77 Posted March 10, 2012 Report Share Posted March 10, 2012 New(ish) to the forums, so hello to everyone.I've been reading a while and, to be frank, I was hoping I could finish my build using all the advice and examples in here without having to post a question. I really wanted to say "hey guys, look at this. I built it using all the info in here and there's so much I never even had to ask anything." Unfortunately, I think I am trying to move outside the norm a little. What I mean is, I am turning into a picky little bastard. What I really want is a 20-22 inch barrel that has a mid-length gas system. However, I can't seem to find a gas system on the 20+ barrels that isn't rifle-length. I have the MA-TEN rifle length monolithic upper and really want the gas block hidden under the rail. I have seen instances where people say the company making their barrel needs a length specified for the build. Does anyone have any ideas on where I can find what I am looking for, or can someone recommend a place that will cater to my somewhat odd needs (wants)?Thanks for any help anyone can give and glad you are all here for questions like this. Quote Link to comment Share on other sites More sharing options...
imschur Posted March 10, 2012 Report Share Posted March 10, 2012 Did you get your Mega hardware from Dave here at the site? I believe he is also working with a custom barrel manufacturer. Quote Link to comment Share on other sites More sharing options...
teedge77 Posted March 10, 2012 Author Report Share Posted March 10, 2012 No, got an upper lower set from MidwestPX. Lower is finished and BCG is on backorder. Just need to get the barrel, gas block, and tube. Then it'll at least be shootable. (Although still needing a lot more, I'll feel good about it being "shootable".) Quote Link to comment Share on other sites More sharing options...
imschur Posted March 10, 2012 Report Share Posted March 10, 2012 Contact Branson1369 (Dave). You can find his info in the for sale board. Dave supplied most members here withthe Mega stuff. I believe he also has access to custom barrels. Quote Link to comment Share on other sites More sharing options...
teedge77 Posted March 10, 2012 Author Report Share Posted March 10, 2012 Thanks for the help; I sent him a PM. I am going nuts looking for a barrel and I hope he (or someone else reading this) has some good news for me. Quote Link to comment Share on other sites More sharing options...
robtmc Posted March 11, 2012 Report Share Posted March 11, 2012 Just to be contrary, and out of curiosity, why do you want a mid-length gas system with a longer barrel?From what I have read, there is an optimum length of barrel beyond the gas port for optimum dwell time, and a 20"+ barrel may be out of bounds here. Quote Link to comment Share on other sites More sharing options...
unforgiven Posted March 11, 2012 Report Share Posted March 11, 2012 Welcome from Indiana brother teedge. Quote Link to comment Share on other sites More sharing options...
teedge77 Posted March 11, 2012 Author Report Share Posted March 11, 2012 A 20 inch barrel is my sweet spot for accuracy/aesthetics. The mid-length gas system is aesthetically important to me as it will hide the gas block under the handguards.As far as dwell time, I think you may have it slightly reversed. In the case of a rifle-length gas system and a 16.5 inch barrel, you would then not have enough dwell time. Lengthening the barrel a couple inches will increase the dwell time and then you can pretty easily adjust the gas block/pressure back some (decreasing it) as/if needed. Even a 26 inch barrel and a mid-length gas system wouldn't suffer terribly from dwell-time issues. The length of time that gas is coming back through the gas tube will not outlast the cycling of the bolt. (You won't have gas coming out of the tube still when the bolt returns.)Please, if this is incorrect...someone set me straight. Thanks.Also, thanks for the welcome unforgiven. Quote Link to comment Share on other sites More sharing options...
teedge77 Posted March 11, 2012 Author Report Share Posted March 11, 2012 Hmmm... to better qualify this, think of it this way instead "there is an optimum length of barrel beyond the gas port for minimum dwell time" Quote Link to comment Share on other sites More sharing options...
robtmc Posted March 11, 2012 Report Share Posted March 11, 2012 I got to reading about this, being someone with a carbine length system and feeding issues. My take was rule of thumb is around 6-7" of barrel past the port for reliable dwell and operation. Gas port size is also a variable, which may have been my problem with a 16" barrel and small .063" port. What I read is that other dwell times can be tuned for with gas restriction or opening if it comes to that, with a limitation on orther loads that cycle well. Very short barrels were the prime culprit. Can be tuned for one load, but others are in the twilight zone for reliability. Read about someone wanting to cut down a 24" with rifle length gas and asking about problems. YMMV, that was the take home for me about barrels and gas port/size location. Sounded like more art than science.Hmmm... to better qualify this, think of it this way instead "there is an optimum length of barrel beyond the gas port for minimum dwell time" Quote Link to comment Share on other sites More sharing options...
teedge77 Posted March 11, 2012 Author Report Share Posted March 11, 2012 I probably should have said "to meet the minimum dwell time." It sounds like we are on the same page though. Too short of a barrel and/or too small of a gas opening can be a problem. Quote Link to comment Share on other sites More sharing options...
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