Gas port off center questions

[darkfader]

Hey guys, I’ve got a few questions for the more experienced AR builders.
I decided I wanted a MK12-ish clone so started collecting parts. Aero receivers, BCG and associated parts kits. A2 stock, rifle buffer and spring, lo-pro gas block and chrome tube, Knights rifle RIS, Allen engineering brake and collar to accept the AEM5 form 1 clone I had also planned. And finished with the problem child, a Ballistic Advantage 18” SPR Ops Inc. contour barrel
I used feeler gauges to determine gas block distance off the shoulder of the gas block journal and carefully lined up the gas block to top dead center and tightened the set screws. The rifle never cycled properly. Sometimes it would strip a second round off the mag, it would never lock back on an empty mag.
Wasted a lot of time messing with buffer weights and every different ammo I could get my hands on. Just wouldn’t work.
Unbelievably frustrated, I decided to put an AGB with a new tube on it. This time I used my dimple jig to be sure the gas block was properly aligned. This is when I finally notice that the gas port is not top dead center. It’s closer to 11 o’clock when looking down the barrel. I went ahead and installed the new AGB and headed to the range for testing. It is now truly semi-auto and locks back with all different ammo from tulammo, to PMC, win, etc and grains from 55-77gr. The BCG seems to move in the upper with no drag.
My questions are, do I need to be concerned with the canted gas block and associated angle of the gas tube where it enters the gas key? Who else makes an SPR contour barrel that I can depend on ports and index pins being in the same plane?
I sent a support ticket to BA, so I’m hoping to hear back from them. I know some folks don’t care for BA, but I have many AR builds using aero and BA and they all work just fine. I’m just curious of the groups thoughts on this.
Sorry for the mini-novel, but was hoping to get some guidance. Thanks for any tips and insights.

 

[TonyTheTiger]

My questions are, do I need to be concerned with the canted gas block and associated angle of the gas tube where it enters the gas key? Who else makes an SPR contour barrel that I can depend on ports and index pins being in the same plane?

Depends on how extreme the angle is where the tube enters the key. If it functions fine now and your life doesn't depend on this rifle I'd just run it and see if the tube starts wearing excessively on one side. If you're OCD and it'll always bug you just get BA to make it right now.
Any barrel company should be trusted to properly center things, even BA as long as it's a Tuesday-Thursday barrel.

 

[BCP]

Post up some pics of how offcenter it is. If it's that bad it should be easy to see in relation to your handguards. The barrel extension is all lined up right? No feed ramps clocked funny?

 

[Snuby642]

I have a pile of bargan barrels that I have used. So far none have been misaligned enough to spot on a visual inspection.

I bet tripple T is right and they would take it back.
I would hate to have a failure even if only precious range time.

 

[darkfader]

Yea it’s definitely just a range toy, but I like things to be right. Here are a few pics and I probably made it sound worse than it is. It’s filthy from testing yesterday, but clearly canted at the port:

The tube appears pretty straight once in the receiver, and like I said, I don’t notice any drag or hang ups when the carrier is slid back and forth by hand

Feed ramps aren’t too bad I guess, but not amazing IMHO

This is their “performance series” and of course they’re out of stock on the site. Lol. I always use a reaction rod to tighten barrel nuts so I can’t imagine I did any harm to the extension on install. Indexing pin slot of the receiver looks new as of yesterday when I took the thing apart.

 

[mtrmn]

It may be my imagination but the feed ramps do appear to be rotated slightly counterclockwise. Is it possible that the slot in the upper receiver for the alignment pin is off slightly?

 

[6.5SH]

"Who else makes an SPR contour barrel that I can depend on ports and index pins being in the same plane?"

PRI sells the Douglas barrels used in the real Mk12's, Compass Lake and White Oak also offer that profile.

 

[whatsupdoc]

Without disassembling the upper and checking each individual component it would be difficult to
determine what part or combination of parts is the cause.

If the problem is the BA barrel they will replace it, may take a few months as did mine but nothing
you can really do if they dont have any.

 

[Hobo Hilton]

Loosen the gas block. Plug one end of the barrel. Blow through the other end while moving the gas block around. When you find the sweet spot with the least amount of resistance (back pressure).... Where is the gas block located ? If it's anywhere close to where it needs to be. Lock it down and go fire the weapon.

You guys just go ahead and laugh or criticize.

 

[darkfader]

I’ll wait to see what BA has to say about it, but I’ll probably look into a Douglas, compass lake or white oak in the meantime. The photo of the feed ramps is a little deceiving compared to looking at it in person. The left edge of the left ramp doesn’t match the ramp in the receiver very well, like there’s a little extra material, but the other three corners line up pretty well. I’d imagine a little massaging of the ramps would clean that right up, but I don’t see a need to mess with that since there’s never been a feed issue with many different types of ammo, just the undergassed non-cycling. The indexing pin is a snug fit in the receiver slot so it doesn’t appear to be damaged. Just putting a straight edge along the stamp on the top of the barrel shows the gas port closer to 11 o’clock which I just didn’t notice during the initial assembly. I can live with a canted block I suppose as long as everything is safe and works as it should. The suppressor will be done this week so there’s another round of adjustments it’ll need I assume. Im tempted to put the original gas block on it using the dimple and see how it acts suppressed.

 

[TonyTheTiger]

White Oak has an awesome sale going right now.

 

[darkfader]

White Oak has an awesome sale going right now.

I see their barrel is even cheaper than BA with that sale price. Looks like 16 weeks lead time which wouldn’t matter to me. Anything I need to know about the Wylde chambering? I don’t own any barrels in Wylde

 

[TonyTheTiger]

Anything I need to know about the Wylde chambering? I don’t own any barrels in Wylde

Nope. The chamber difference is insignificant for 99% of shooters.

 

[darkfader]

Thanks man. If you guys like the White Oak, I’ll just back order one today. That’s easy enough. Shoot with a canted block until then.

 

[TonyTheTiger]

I don't personally own a White Oak, but years of membership on various forums tell me they've got a great reputation.

Edit to add, I do own the exact same BA barrel. It shoots pretty well and must not be a Monday morning or Friday afternoon barrel, everything is how it should be.

 

[BCP]

I've had several of those 18" barrels and never had one all fucky like that. Something is off either your index pin or gas port or your upper? Unless the gas block has an offcenter hole lol.

 

[Dino11]

Gas tube was probably rubbing the gas key.