Trouble Adjusting Superlative Arms Gas Block

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Peirsonb

Inactive
This seems like a silly problem to have given that we're not talking about rocket surgery, but here I am....

The rifle is a Bushmaster ORC. I changed out the furniture for Magpul, but other than that the rifle is stock. My ammo of choice is American Eagle 55gr .223.

I got a Superlative Arms gas block for Christmas. I heard nothing but good things when they were produced under Syrac, so that's what I asked for. Yesterday was my first chance to tune it and I'm running into issues.

Their included instructions are reverse from most of what I see in online circles. Rather than work up from full closed they recommend working down from full open. So that's the procedure I followed.

I fired my shot, bolt locked, so I closed it half a turn (two clicks) per the directions. I repeated until the bolt didn't lock back. Normal.

I opened it two clicks from there, to the last "bolt lock" position and it didn't lock back. I opened it another two, and it didn't lock back. I was almost full open before I got out to lock again. When it locked I repeated and started to close it. The bolt continued to lock PAST where I was when it failed to lock the first time.

When it failed to lock I started to open it. Two clicks, still no lock. Two more clicks, still no lock. And another two....

When I got back to a lock position I started to close it again. Two clicks and it locked. Two clicks and it locked. Again, I ended up PAST where I was before it failed to lock.

I just can't seem to get repeatable results. I know there will be pressure differences between rounds, but I would think it should be pretty repeatable, within a half turn, of locking and not locking.

I stripped the upper and I'm not feeling any interference between the bolt carrier and gas tube. I pulled the charging handle and the bolt does lock on an empty mag that way.

At ALL positions (i never got to full closed), whether the bolt locked or not, the rifle ejected the casing. I can tell the gas block is doing something because the ejection pattern changed throughout.

Almost a full box of ammo in and I just can't seem to get it tuned for minimum gas AND get that bolt to lock.

Is there something simple I'm missing?
 
I don't know. I'm not familiar with what you are working with...however,

As a machinist,I am in the habit of stopping while going clockwise every chance I get.(Or,Counterclockwise if your situation requires.Just always the same)

You might want to be sure its clear of grease,chips,burr,etc.And that the gas port in the barrel is aligned with the gas block port.

Adapt to your needs,but suppose I'm "out" (CCW) 12 clicks.I'm adjusting "In" (CW) 2 clicks at a time. At 8 clicks "IN",it fails to catch the bolt stop. So,you want to go "OUT" 2 clicks(CCW) Instead of just going OUT 2 clicks,(CCW),go "Out " 6 clicks,(CCW),then come back 4 clicks "IN" (CW)

That way the screw and the slack are always stopping in the same direction.

That's how its done in a mill or lathe.

I have no idea if that will help with your gasblock.
 
I'll give it a try. I get taking the backlash out of the screw, I'm not sure it'll help in this case. The adjustment screw is detented every quarter turn. The most it "should" move on its own is whatever slop is in the detent slot (I can feel some).

But it's better than any ideas I've got. I'll give it a shot.

As far as alignment with the gas port, I'm not sure how to do that any better than I did. The hole is the gas block itself its MASSIVE compared to the port in the barrel. I'd say about 0.100" in the block compared to 0.040" ish in the barrel (I didn't gage either). That, visually sighting it square with the upper, and making sure there's no bind on the bolt carrier group are about all I can think to check.
 
@Mobuck

That's part of the problem. I'm not working from full closed, I'm working from full open. When I get the bolt to NOT lock back I have to open it some. Way PAST where I was when it failed in the first place.
 
Perhaps you might want to try stripping it down, removing the gas block, scrupulously cleaning and degreasing everything, then CAREFULLY reassembling to whole thing. Yes, it can be a pain but I've found this basic method to be best when working on things such as a new build computer. Although they are far from the same animals, the same logic still applies; work slowly and methodically in a 'scientific' way. You might even want to keep notes or a log of what you are doing on a step by step basis and the results thereof. I've found this helps when it comes time to figure out what isn't working properly.
 
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