How serious are you about aligning your gas block?

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Posted: 1/6/2019 10:42:08 PM EDT

Put together an upper today. It's not my first, but I watched a video on gas block alignment and seating. It got me thinking. Usually what I do is fit the gas block on the barrel before anything else is installed, and plug the bore with my thumb and blow into the chamber. I'll move the block back and forth and rotate it to get a feel of where it blows through the best. Almost always there is such a huge range of rotation where it feels fine that I don't worry about making any sort of serious markings or anything. When I put them on almost always once the gas tube is installed and inserted into the upper, it is within the acceptable blow test rotation and I just screw the gas block down.

I've done a ton of uppers like that and never had any sort of issue. However I read a ton of people go through crazy procedures to ensure it is aligned absolutely perfectly. Seems like a waste of effort to me. What about you?

Posted: 1/6/2019 10:46:34 PM EDT

[#1]

I'm fussy enough about it to have purchased a Lyman Borescope.

It's a useful tool if you like to know what's going on inside your bore, although I could wish the resolution was a little higher.

Posted: 1/6/2019 10:48:00 PM EDT

[#2]

I eyeball it. No issues yet.

Posted: 1/6/2019 10:49:03 PM EDT

[#3]

Quote History

Quoted:

I'm fussy enough about it to have purchased a Lyman Borescope.

It's a useful tool if you like to know what's going on inside your bore, although I could wish the resolution was a little higher.

View Quote

I have one of those! I never thought about using it. That's genius.

Posted: 1/6/2019 11:01:26 PM EDT

[#4]

Quote History

Quoted:

I'm fussy enough about it to have purchased a Lyman Borescope.

It's a useful tool if you like to know what's going on inside your bore, although I could wish the resolution was a little higher.

View Quote

This right here no doubt things are lined up .

Posted: 1/6/2019 11:04:04 PM EDT

[#5]

Based on KAC and from what I can tell Q's focus on it, it's an important point if you're trying to get that je need see quoi smoothness. That said we'll never get tapered and cinched proprietary fitting like they do even with perfect alignment and some sort of sealant.

So meh.

Posted: 1/6/2019 11:05:39 PM EDT

[#6]

I am pretty OCD. Including the gas tube match up with the BCG. I usually end up making tiny adjustments on both to get that buttery smooth hook up.

Posted: 1/6/2019 11:05:47 PM EDT

[#7]

I don't put much thought or effort into it. Never had any issues.

Posted: 1/6/2019 11:07:57 PM EDT

[#8]

Very serious

Posted: 1/6/2019 11:08:36 PM EDT

[#9]

For set screw blocks I use BRD engineering dimpling jig. It works. For clamp on blocks I use a soda straw to blow in from the chamber end and a plug in the muzzle to gauge alignment.

Posted: 1/6/2019 11:17:38 PM EDT

[#10]

Quote History

Quoted:
Based on KAC and from what I can tell Q's focus on it, it's an important point if you're trying to get that je need see quoi smoothness. That said we'll never get tapered and cinched proprietary fitting like they do even with perfect alignment and some sort of sealant.

So meh.

View Quote

If a guy wanted, he could add a pin to any gas block then slot the barrel's shoulder to accept.

I drill my dimples or taper pins in the mill, pretty easy to get it aligned very closely.

Posted: 1/6/2019 11:21:49 PM EDT

[#11]

I play around with it until the tube is as aligned with the gas key on the BCG as possible, based on how much it moves when pushing the BCG forward (obviously very little movement).

Posted: 1/6/2019 11:22:08 PM EDT

[#12]

I am very serious about it. I own all four sizes of SLR alignment jigs. I have over 200 installs documented on the 0.750" jig.

Does perfect alignment matter? Not really on a carbine length 5.56 gas system. Plenty of room for error. However, when you build uppers for a living you shoot for 110% on 100% of what you do.

Posted: 1/6/2019 11:23:11 PM EDT

[#13]

Eyeball close, works every time.

Posted: 1/6/2019 11:25:32 PM EDT

[#14]

I mark the mid-line on the block, mark the mid-line on the barrel, line up the marks. Easy peasy.

Posted: 1/6/2019 11:27:39 PM EDT

[#15]

i bought a $30 jig so i can dimple the barrel and never have to worry about it

Posted: 1/6/2019 11:31:26 PM EDT

[#16]

I index mine by length and for rotation I use a digital angle finder. Easy.

Posted: 1/6/2019 11:32:10 PM EDT

[#17]

I eyeball then testfire then dimple, hasn't failed me yet.

Posted: 1/6/2019 11:32:32 PM EDT

[#18]

Donut wear on the gas tube is a real thing. But what the fuck do I know?

Align that shit perfect with the gas key rather than the barrel thats why the opening on both the gas block and gas tube are over sized.

Posted: 1/6/2019 11:33:24 PM EDT

[#19]

Quote History

Quoted:
i bought a $30 jig so i can dimple the barrel and never have to worry about it

View Quote

Dimple is not needed .....but again what the fuck do I know.

Posted: 1/6/2019 11:34:58 PM EDT

[#20]

Quote History

Quoted:
I mark the mid-line on the block, mark the mid-line on the barrel, line up the marks. Easy peasy.

View Quote

Pretty much this.

Posted: 1/6/2019 11:37:03 PM EDT

[#21]

So serious that I eyeball it and crank it on down. Sometimes if I’m super cereal about it I’ll plug the chamber end of the barrel with my palm and blow down the barrel end to see if air comes out the gas block. Does this actually work to test gas flow? Dunno. But I’ve never had any issues so far.

Posted: 1/7/2019 12:57:14 AM EDT

[#22]

Quote History

Quoted:
Donut wear on the gas tube is a real thing. But what the fuck do I know?

Align that shit perfect with the gas key rather than the barrel thats why the opening on both the gas block and gas tube are over sized.

View Quote

Who is paying attention to the gap off the shoulder that is a design dimension for the handguard cap? So the gas key doesn’t push on the gas tube and tension the barrel?

Posted: 1/7/2019 1:01:48 AM EDT

[#23]

Built 5 ARs before I ran into a problem. The 6th AR wouldn't cycle right, and after ruling a couple of things out I figured it had to be the block alignment. Sure enough, for some reason the block didn't line up all the way pushed against the shoulder. I just shot it a few times and moved it slightly until it cycled well.

Posted: 1/7/2019 1:12:25 AM EDT

[#24]

I take a tooth pick and drop it in the hole on the barrel and cut it off just below flush with some diagonal cutters. Slide on the gas block and rotate the barrel upside down until the tooth pick drops into the gas block. Wiggle side to side to make sure it doesn't bind. Lock it down.
Finally, drive out the tooth pick with a cleaning rod.

Posted: 1/7/2019 1:19:10 AM EDT

[#25]

Quote History

Quoted:
I take a tooth pick and drop it in the hole on the barrel and cut it off just below flush with some diagonal cutters. Slide on the gas block and rotate the barrel upside down until the tooth pick drops into the gas block. Wiggle side to side to make sure it doesn't bind. Lock it down.
Finally, drive out the tooth pick with a cleaning rod.

View Quote

they sell pin kits for that

Posted: 1/7/2019 1:20:21 AM EDT

[#26]

Quote History

Quoted:
I take a tooth pick and drop it in the hole on the barrel and cut it off just below flush with some diagonal cutters. Slide on the gas block and rotate the barrel upside down until the tooth pick drops into the gas block. Wiggle side to side to make sure it doesn't bind. Lock it down.
Finally, drive out the tooth pick with a cleaning rod.

View Quote

Genius.jpg

Posted: 1/7/2019 1:23:23 AM EDT

[#27]

Done it twice now and the first time I read some where to use a pencil and mark a line where the holes are. I did that on the barrel but I marked the outer edge of both sides and the center, drew a line long enough to go past my gas block and marked the front of the gas block in the same manner, can barely see the pencil though.

Posted: 1/7/2019 1:24:27 AM EDT

[#28]

For set screw, I verify that the rear hole lines up with the block port with a toothpick. Then, I put the block on upside down and center the barrel port in the rear screw hole. I then mark the barrel and turn the block over. After that the block gets adjusted so that the tube doesn't bind in the receiver. Then the front screw gets tightened, and the rear hole is used to mark the barrel for a dimple. This process takes little time and works well. If the rear hole doesn't line up with the block port, I got nothing.

Posted: 1/7/2019 1:24:51 AM EDT

[#29]

I’m kind of OCD, but you can eyeball it and get it probably within a degree or two

I just use a pencil and mark the barrel and mark the gas lock and line them up

Posted: 1/7/2019 1:27:08 AM EDT

[#30]

Quote History

Quoted:
they sell pin kits for that

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
I take a tooth pick and drop it in the hole on the barrel and cut it off just below flush with some diagonal cutters. Slide on the gas block and rotate the barrel upside down until the tooth pick drops into the gas block. Wiggle side to side to make sure it doesn't bind. Lock it down.
Finally, drive out the tooth pick with a cleaning rod.

they sell pin kits for that

Tooth pick is essentially free.

Posted: 1/7/2019 1:32:14 AM EDT

[#31]

Quote History

Quoted:
I have one of those! I never thought about using it. That's genius.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:

I'm fussy enough about it to have purchased a Lyman Borescope.

It's a useful tool if you like to know what's going on inside your bore, although I could wish the resolution was a little higher.

I have one of those! I never thought about using it. That's genius.

Genius?

I dunno about that...I just walked out into the kitchen. When I got there I realized I had no idea what I was looking for.

Posted: 1/7/2019 1:53:20 AM EDT

[#32]

Quote History

Quoted:
I take a tooth pick and drop it in the hole on the barrel and cut it off just below flush with some diagonal cutters. Slide on the gas block and rotate the barrel upside down until the tooth pick drops into the gas block. Wiggle side to side to make sure it doesn't bind. Lock it down.
Finally, drive out the tooth pick with a cleaning rod.

View Quote

Dry pasta works too.

Posted: 1/7/2019 9:42:58 AM EDT

[#33]

Quote History

Quoted:
Dry pasta works too.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
I take a tooth pick and drop it in the hole on the barrel and cut it off just below flush with some diagonal cutters. Slide on the gas block and rotate the barrel upside down until the tooth pick drops into the gas block. Wiggle side to side to make sure it doesn't bind. Lock it down.They
Finally, drive out the tooth pick with a cleaning rod.

Dry pasta works too.

Linguine. It's like the rocksett of gas block alignment. Just soak in water overnight to get out.

Posted: 1/7/2019 10:26:55 AM EDT

[#34]

I have had issues.

I generally use a marked to mark top dead center on the shoulder behind the gas block, then slide the gas block into position and tighten down the set screws. I do the plug/blow method in the house, or use the compressor if I'm at the garage to check air flow (feel and noise/sound.)

Then I remove the loosen the screws, slide the gas block forward, make a start with a center punch and drill the back hole just a tad to give the set screw a good spot to lock in. Then I move the gas block back, tighten down the rear screw, remove the front screw and insure the alignment of the hole in the gas block and the mark on the barrel from that first tightening is still good. If so, I loosen the back set screw, move the gas block forward again and then dent/drill the front hole just enough to give that screw a good bite. Then I move the gas block back into place, tighten up both set screws and put the free float tube on it.

The one issue I had with alignment was the last build where I got pinched bad (between the block and the shoulder and was bleeding all over everything and got hot, sweaty, bloody and aggravated and left the block snug up against the shoulder. It short stroked almost every time. Every now and then it would blow the bolt back far enough to pick up the next round, but seldom. Fought it a couple range sessions and then was reminded of the "gap" between the gas block and barrel shoulder. Corrected that and the next range session it was 100% functional.

Posted: 1/7/2019 10:31:47 AM EDT

[#35]

My 300 BLK needed precise alignment to get all the gas possible to work the action subsonic.

Ended up using a PSA block since they are fairly wide in the gashole

Posted: 1/7/2019 10:35:38 AM EDT

[#36]

I'm more concerned about alignment of the iron sights. So I line my gas block up so that the front sight tower is perpendicular to the tlat top rail. Unless I'm using a low profile gas block and a free floating handgaurd. Then I just eyeball it.the port in the gas block is usually about twice the size of the port in the barrel, so there's some margin of error allowable.

Posted: 1/7/2019 10:41:17 AM EDT

[#37]

Quote History

Quoted:
Tooth pick is essentially free.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
I take a tooth pick and drop it in the hole on the barrel and cut it off just below flush with some diagonal cutters. Slide on the gas block and rotate the barrel upside down until the tooth pick drops into the gas block. Wiggle side to side to make sure it doesn't bind. Lock it down.
Finally, drive out the tooth pick with a cleaning rod.

they sell pin kits for that

Tooth pick is essentially free.

Gas block hole is a lot bigger than the hole on the barrel. So all you're doing is adding extra work for yourself.

Posted: 1/7/2019 10:47:51 AM EDT

[#38]

Yea I don’t even do that. It’s more of “yep that looks right” and move on

Posted: 1/7/2019 10:53:21 AM EDT

[#39]

I do pretty much same as OP. Lots of good ideas here!

Posted: 1/7/2019 10:54:12 AM EDT

[#40]

Quote History

Quoted:
I eyeball it. No issues yet.

View Quote

Same.

Posted: 1/7/2019 11:02:43 AM EDT

[#41]

ITT, we meet all the people that are the reason dumb AR products on the market exist.

Really people?
C'mon, it's a hole in a tube over a stick with a hole in it...
All you have to do is line them up - it's not rocket surgery.

Better yet, when you buy quality parts, merely installing things straight means they're going to line up.

Posted: 1/7/2019 11:07:39 AM EDT

[#42]

Quote History

Quoted:
I eyeball it. No issues yet.

View Quote

I mark the barrel and gas block with a pencil. Align the pencil marks, good to go.

Posted: 1/7/2019 11:12:10 AM EDT

[#43]

Eyeball for like three seconds. Never had a problem. No idea how many I've done.

Posted: 1/7/2019 11:13:02 AM EDT

[#44]

i don't mind if it's a bit crooked

usually i'll just mount my mawl and do a nice 5' drop to get it into alignment

Posted: 1/7/2019 11:20:06 AM EDT

[#45]

Barrel shim and a center mark should be all that’s needed with a quality gas block and barrel.

Posted: 1/7/2019 11:20:33 AM EDT

[#46]

I make sure the barrel is dimpled, which has been square on the two times I've had dimpled barrels get gas blocks with set screws.

Saddly though, set screws aren't rugged enough for military grade weapons, and should be pinned.

Non-dimpled with set screws is just asking for trouble.

Posted: 1/7/2019 11:22:27 AM EDT

[#47]

I'm hardly qualified to comment, as I've only built one AR. I stupidly and purposefully misaligned the gas block while assembling my upper, in the attempt to get the end of the gas tube to have minimal interference with the gas key as the BCG slides forward. In my ignorance at that time, I didn't know you could gently bend the gas tube to get the same result. So now my gas block is about 2 degs misaligned off perfect vertical. My gas block is dimpled and set-screwed in place. However, as the gun cycles perfectly and I don't see any other issues, I'm not going to attempt to fix it. It bugs me knowing it's there, but I'll do it perfect on my next built, live and learn.

Posted: 1/7/2019 11:31:52 AM EDT

[#48]

Most of the time if I rotate the gas block upside down with screws removed I can see the gas port through the set screw hole. I line everything up and mark midlines with pencil. Then I'll measure the small distance it's set back from the shoulder. Spin the gas block 180 degrees, line up marks, check the distance from the shoulder, and tighten it down.

To verify I plug the chamber end of the barrel with a paper towel, put a speck of paper towel next to the chamber end of the gas tube, and blow air into the muzzle end. If it's lined up right the small piece of paper next to the gas tube will blow out of the upper.

Sounds dumb but it works.

ETA: Once I build one and use it awhile, satisfied that I like the upper & decide it's a keeper, I'll send it off to have it pinned.

Posted: 1/7/2019 11:37:26 AM EDT

[#49]

Quote History

Quoted:

Dimple is not needed .....but again what the fuck do I know.

View Quote

Henderson Defense posted that their set screw gas blocks on undimpled barrels have held up for thousands of rounds. Their observation was that the carbon basically seals the block/screws in place.