Help installing AR gas block

[rocketsci]

So...

I'm in the process of building (ok, assembling) my first AR, and I'm at the point of putting a low-profile gas block on my new WOA 18" SPR barrel. When I did a fit check, the gas block doesn't slide all the way down to line up with the gas port on the barrel. It looks like the barrel might have an ever so slight "ramp" in the diameter, which might make a better gas seal, but is definitely going to make putting that as block on a pain.

Has anyone else experienced this? Any pointers on how to line up the gas block with the gas port when there is a press fit?

Thank you! I'll work on getting some pictures and dimensions posted later today.

[wash]

Try sliding it on backwards, if it stops at the same point, it's a taper in the barrel. If it stops further forward, it's probably a taper in the gas block bore.

If it's really close you could try to lap them together.

If you don't want to do that, determine which part has the taper and send it back to the manufacturer for replacement or repair.

Good luck sorting it out.

[Nathan Krynn]

It is a tight fit for the reason you stated, to prevent gas leakage.

Make sure you unscrewed the set screws first.

Oil the barrel.

I use a piece of PVC pipe I think it is 1" and a rubber mallet to get them on all the way.

[ott1]

Better yet, put the barrel in the freezer and the gas block in the oven. Or put a torch to the gas block and heat it up. It should expand enough that it will slip on.

[rocketsci]

It is a tight fit for the reason you stated, to prevent gas leakage.

Make sure you unscrewed the set screws first.

Oil the barrel.

I use a piece of PVC pipe I think it is 1" and a rubber mallet to get them on all the way.

Thank you!

The set screws were removed, but it never hurts to double check.

I was thinking of oiling the barrel, but I wasn't sure if that would reduce the gas seal. On second thought, we use oil for seals ~all the time~. I'm an idiot...

Any advice on how to line up the gas port? The fit is tight enough that rotating the gas block later might be difficult. I was thinking of marking the barrel in line with the port, and trying to keep the block aligned to my marking. Is there an easier way?

Thank you for the PVC tip, I was originally planning on a wood block. The PVC sounds better.

-Joe

[rocketsci]

Better yet, put the barrel in the freezer and the gas block in the oven. Or put a torch to the gas block and heat it up. It should expand enough that it will slip on.

That's sounds interesting! Now where did I put that torch...

[Nathan Krynn]

Yeah the PVC works like a charm.

Check your barrel. A lot of barrel makers dimple where one of the set screws will go.

If not don't fret so much over lining it up. Do your best to eyeball that the gas tube is straight and not canted and the gas block doesn't look canted and you are set. You do not need 100% of that gas anyway.

[Lostsheep]

Yeah the PVC works like a charm.

Check your barrel. A lot of barrel makers dimple where one of the set screws will go.

If not don't fret so much over lining it up. Do your best to eyeball that the gas tube is straight and not canted and the gas block doesn't look canted and you are set. You do not need 100% of that gas anyway.

I've been wondering about this. I know the shoulder on the barrel provides the front to rear location, but I did not know what provided the rotational alignment. Are you saying that "eyeballing" is close enough for that?

[1911su16b870]

If the low profile gas block has socket head cap screws that tighten it on the barrel I take the screws out, then thread it in though the opposite side onto a penny or nickle (whatever fits) and then it will open up the block so that you can easily position it on the barrel.

I always check barrel/block port position by running shop air into the barrel while plugging the chamber and listening to the sound through the block/gas tube.

Good luck.

[rocketsci]

If the low profile gas block has socket head cap screws that tighten it on the barrel I take the screws out, then thread it in though the opposite side onto a penny or nickle (whatever fits) and then it will open up the block so that you can easily position it on the barrel.

I always check barrel/block port position by running shop air into the barrel while plugging the chamber and listening to the sound through the block/gas tube.

Good luck.

Thanks!

Unfortunately, I've got a YHM low profile block that uses set screws and a matching dimple in the barrel, not a clamp-on block.

[rocketsci]

Yeah the PVC works like a charm.

Check your barrel. A lot of barrel makers dimple where one of the set screws will go.

If not don't fret so much over lining it up. Do your best to eyeball that the gas tube is straight and not canted and the gas block doesn't look canted and you are set. You do not need 100% of that gas anyway.

Yeah, there is a dimple. 2, actually, one for each set screw.

I think I've been spending too much time reading the M4carbine forum, and getting paranoid about actual vs nominal port size, etc...

Thank you for your advice Nathan! One of these days I'll go whole hog and order a 80% lower (and jigs) from TM...

-Joe

[Nathan Krynn]

No problem I come on here to help guys like yourself.

Yeah your WAY over thinking it. If you have 2 dimples then it is as easy as putting the screws into the dimples. I am kind of amazed you have two.

I dimple my own barrels if there are none there but rarely do both even on my personal guns.

[rocketsci]

Heh. I'm an engineer, overthinking things is an occupational hazard.

So, as it turned out, all I needed to get the block installed was a little oil on the barrel and some elbow grease. I got the block lined up with the dimples, pushed slowly, and had to twist the block just a little to keep it lined up with the dimples.





Thanks to everyone for your advice! Now to wait for the handguard...

-Joe