kasen Posted January 14, 2018 Share Posted January 14, 2018 After 6 years of multigun my 18" Noveske Rogue Hunter upper is shot out. I decided to build an upper with a CMT billet upper, Ballistic Advantage 18" fluted barrel, Seekins adjustable gas block, and low mass RCA BCG, This is mated to the existing Noveske lower (which was very reliable with the 18" intermediate gas barrel) and has a Magpul UBR stock (carbine length), standard carbine buffer spring and Spikes ST-T2 buffer. During assembly I realized the old 18" Noveske barrel was an intermediate gas system, NOT rifle length. The new Ballistic Advantage barrel is a rifle length system and it is short stroking. I opened up the Seekins gas block all the way, swapped in an H buffer and eventually went down to a 3oz buffer. With relatively hot 77gr loads the rifle cycles, but with normal 55gr ammo it short strokes to the point where it rarely grabs the next round. I'd prefer to keep the UBR stock if possible. I read that the JP captured spring buffer system may be a solution, but before I invest that cash I am curious if there's a better solution. Although it is a dedicated competition gun reliability still matters. It seems opening up the gas port may be the other solution, besides converting a rifle length buffer tube. Is there anything else I should consider? Link to comment Share on other sites More sharing options...
TonytheTiger Posted January 14, 2018 Share Posted January 14, 2018 Did you check gas block alignment? Link to comment Share on other sites More sharing options...
kasen Posted January 14, 2018 Author Share Posted January 14, 2018 This is the first upper I've built, so Im not sure if it is correctly aligned. It appears to my eye to be centered. After 20 rounds I am seeing carbon on the gas tube near the upper receiver. Link to comment Share on other sites More sharing options...
TonytheTiger Posted January 14, 2018 Share Posted January 14, 2018 Pull the GB off and see if the carbon ring is roughly centered over the port hole. Link to comment Share on other sites More sharing options...
DesertTortoise Posted January 14, 2018 Share Posted January 14, 2018 It should run great with the parts you have. Alignment of the gas block over the port is probably the problem Link to comment Share on other sites More sharing options...
Vespid_Wasp Posted January 14, 2018 Share Posted January 14, 2018 2 hours ago, DesertTortoise said: It should run great with the parts you have. Alignment of the gas block over the port is probably the problem This. Link to comment Share on other sites More sharing options...
Vespid_Wasp Posted January 14, 2018 Share Posted January 14, 2018 11 hours ago, TonytheTiger said: Pull the GB off and see if the carbon ring is roughly centered over the port hole. And this. Link to comment Share on other sites More sharing options...
kasen Posted January 14, 2018 Author Share Posted January 14, 2018 13 hours ago, TonytheTiger said: Pull the GB off and see if the carbon ring is roughly centered over the port hole. Photo seems to indicate the hole was centered. I can't move the block further to center due to the shoulder on the barrel. Since I'm running a carbine buffer spring is it a bad idea to cut a couple coils? Link to comment Share on other sites More sharing options...
TonytheTiger Posted January 14, 2018 Share Posted January 14, 2018 That looks reasonable. Next I'd check the gas key for tightness. And how old are your gas rings? As stated above your parts combo should work great together without any spring cutting or exotic buffer arrangements. Link to comment Share on other sites More sharing options...
kasen Posted January 14, 2018 Author Share Posted January 14, 2018 52 minutes ago, TonytheTiger said: That looks reasonable. Next I'd check the gas key for tightness. And how old are your gas rings? As stated above your parts combo should work great together without any spring cutting or exotic buffer arrangements. The BC gas key is solid and the rings are brand new. The entire RCA BGC is brand new. I will swap in my old Noveske BGC just to make sure that's not the issue. Link to comment Share on other sites More sharing options...
Dan Sierpina Posted January 14, 2018 Share Posted January 14, 2018 Did you lube the gas rings too? Link to comment Share on other sites More sharing options...
DesertTortoise Posted January 15, 2018 Share Posted January 15, 2018 Could be leaking gas where the gas tube connects to the block? Or the adjustable gas isnt operating correctly Does it cycle smoothly by hand? Could be just a really rough action ? Link to comment Share on other sites More sharing options...
mpom Posted January 17, 2018 Share Posted January 17, 2018 Can you measure the gas port diameter of both barrels? If the BA gas port diameter is significantly smaller than the Noveske's, that is the answer. Would contact BA about it. If the diameters are within 5-7 thousands, then something else is causing the issue. Link to comment Share on other sites More sharing options...
kasen Posted February 25, 2018 Author Share Posted February 25, 2018 Issue resolved. After cutting coils off the spring with a 3oz buffer and still not getting PMC ammo to lock the bolt, I finally ditched the Seekins adjustable gas block. I could see carbon building up on the gas tube near the block, it was clearly leaking. With a non adjustable block everything cycles fine, back to a regular carbine buffer spring and the ST-T2 buffer, and everything cycles great. At this point I'm thinking of leaving it as is, unless others think I'm really missing something with an adjustable gas block. Link to comment Share on other sites More sharing options...
mpom Posted February 25, 2018 Share Posted February 25, 2018 Your call as to whether you need an adjustable gas block, kind of depends on the gas port of your barrel, but obviously not all gas blocks are created equal. JP and SLR are usually GTG. Link to comment Share on other sites More sharing options...
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