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Frankenstein has gas issues

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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?

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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. 

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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.

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11 hours ago, TonytheTiger said:

Pull the GB off and see if the carbon ring is roughly centered over the port hole.

 

 

And this.

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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?

20180114_111307.jpg

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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.

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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.

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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 ?

 

 

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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.

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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. 

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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.

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