Gas Block Alignment Pins

[GrumpyM4]

In 25 years of building AR's, I have never seen a gas block with the same size gas port as the ports on the barrels I've installed the blocks on.

Every single block has had a larger gas port than the barrel to account for manufacturing variance.

The posters who stated that the gas block can be aligned incorrectly yet still allow gas flow are correct.

I've "tried" this little plastic alignment do-hicky and found it severely lacking. I didn't even get to the dimpling portion before throwing these out and grabbing the old faithful alignment jig and starting from scratch.

This product is straight up junk. *ESPECIALLY* if installing a front sight gas block with set screws. Good luck getting your front sight straight without a calibrated eyeball, and even then it's dodgey.

[AndyLate]

IMHO, it's not that hard to mark the top of the barrel with a pencil and straightedge and then center a low profile gas block on the line. I wouldn't try it with a FSB. On the other hand, I don't understand why barrels don't come with a dimple as standard.

Andy

[tehpwnag3]

You'll get a range of answers on this depending who you speak to, most of it is horseshit. Stripped barrels I've bought and/or installed that had a factory dimple opposite the GP worked fine with the GB's spec'd for the project. With that first dimple, the second is easily marked and drilled--no matter the hole spacing--and without needing a jig. To me, if the barrel has a surface treatment, like nitride or park, I'd much rather have at least one dimple treated rather than none. Not a huge deal though.

I've even had a couple barrel companies tell me that dimples are not required to secure a GB. Ok, good luck with that. It might be true, but it's not ideal. Dimples are cheap insurance, and so is Rocksett.

On the other hand, I don't understand why barrels don't come with a dimple as standard.

Andy

[DD_USMC]

Using a straight edge and pencil gets you CLOSE in ONE axis only, but there are more alignment errors made in getting it centered directly over top (forward/aft position).....not left to right, but using a jig ELIMINATES those variables!.

Does gas block fit flush against barrel or do you need a gap?
Is it the gas block or the barrel?
Is it the barrel gas port?
How do you know if the gas block is to far forward or not enough?

I have seen to many variances in parts that cause gassing issues that can be ELIMINATED by installing them CORRECTLY. Continue your "shade tree" assembly or do it right...use a jig!

[the AR-15 Junkie]

Using a straight edge and pencil gets you CLOSE in ONE axis only, but there are more alignment errors made in getting it centered directly over top (forward/aft position).....not left to right, but using a jig ELIMINATES those variables!.

Does gas block fit flush against barrel or do you need a gap?
Is it the gas block or the barrel?
Is it the barrel gas port?
How do you know if the gas block is to far forward or not enough?

I have seen to many variances in parts that cause gassing issues that can be ELIMINATED by installing them CORRECTLY. Continue your "shade tree" assembly or do it right...use a jig!

That point is very good as I have seen gas blocks designed to fit flush against barrel shoulder and others designed to have the gap. Its a shame the maker doesn't tell you on the package as some guidance. If its designed to fit flush and you use it with a handguard cap, that's wrong. And vice versa.

[tehpwnag3]

The easiest way to determine if the GB should have a shoulder gap is to rotate it about the journal 180 degrees, centering the GP inside the corresponding threaded hole. Using a jig precludes having to do this however.

[the AR-15 Junkie]

The easiest way to determine if the GB should have a shoulder gap is to rotate it about the journal 180 degrees, centering the GP inside the corresponding threaded hole. Using a jig precludes having to do this however.

Yeah but your missing my point. If you plan to use a handguard cap and you buy a gas block not designed for it, that's not going to help. It would be better if the makers of the gas block would simply state which style block their selling before you buy it.

[26 Inf]

Yeah but your missing my point. If you plan to use a handguard cap and you buy a gas block not designed for it, that's not going to help. It would be better if the makers of the gas block would simply state which style block their selling before you buy it.

In my experience, the orifice in gas block is ginormous, as mentioned in other posts easily large enough to allow for minor alignment errors. That works fore and aft, as well as port to starboard.

[AndyLate]

Continue your "shade tree" assembly or do it right...use a jig!

Wow, really? Jigs are for production, not assembling a single unit.

Its not rocket science. The gas hole in the gas block (GB) is 180 degrees from the hole in the bottom. The gas port in the barrel is top dead center. A quick check with the GB upside-down determines if a gap between GB and barrel shoulder is required - assuming the barrel has a shoulder.

There is more opportunity for failure marking and drilling the barrel dimples without a jig, but a little care and common sense goes a long way.

All but one of my barrels had had a dimple, pinned gas block, or both. I'm not buying a jig to install a low profile GB on one barrel.

Andy

[tehpwnag3]

Yeah, if you absolutely want to nail that DPMS Oracle clone build.

Yeah but your missing my point. If you plan to use a handguard cap and you buy a gas block not designed for it, that's not going to help. It would be better if the makers of the gas block would simply state which style block their selling before you buy it.