How do I align a clamp-on gas block accuratly?

[BrickShitHouse]

I'm kind of new to building AR uppers and am wondering how to line up the gas ports on the block and barrel. How do you guys do it?

I was thinking of just marking the ports on the outside with a marker...

[Ryno12]

I measured the distance from the shoulder on the barrel to the gas port & the same on the gas block. Align accordingly.

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[BrickShitHouse]

I measured the distance from the shoulder on the barrel to the gas port & the same on the gas block. Align accordingly.

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Thank you sir

[Iraqgunz]

I strongly encourage you to use a gas block with set screws. Make sure the screws have the little teeth to allow them to dig into the barrel. Ideally I would make sure it is dimpled.

[mark5pt56]

This is what I do-I place a mark using a pencil on the block, indicating the center of the port and then draw a line line using a straight edge to indicate the center of the barrel's gas port, place a mark on the barrel's shoulder. Most blocks are designed to go on a barrel that had the handguard end cap removed. Leave that thickness of a HG cap in between the shoulder and block. Never had a problem this way. If unsure, you can always measure the distance from shoulder to center and same for block.

I would dimple the barrel once mounted and tested, one trick is to stake the set screws once tightened. Of course, I always have it pinned.

Hope that helps.

[SCatalyst]

I swear to God, true story. I was in a shop just recently and the smith said, 'I put my lips around the gas tube and blow til I find the sweet spot (least resistance).'

The guy was an prior service old timer, obviously already set in his ways. So I didn't make fun of him, but it did take a lot to hold my composure.

[skijunkie55]

I swear to God, true story. I was in a shop just recently and the smith said, 'I put my lips around the gas tube and blow til I find the sweet spot (least resistance).'

The guy was an prior service old timer, obviously already set in his ways. So I didn't make fun of him, but it did take a lot to hold my composure.

:eek: :lol:

That's awesome...

[Hmac]

The opening in the gas block that covers the gas port in the barrel is substantially larger than the gas port itself. There's some wiggle room in alignment.

IMHO, not that I'm an expert, a clamp-on or even set screw gas block might fall into the category of "maybe good enough". My own goals for the assembly quality of my own rifles have led me to always spend the $30 it costs to get the gas block pinned.

[p22shooter30]

measure, measure, and then re-measure. don't be afraid to use a sharpie on your barrel. what I do is when i think i have it right and tighten the screws, i go shoot it. if it functions correctly, i back each screw out one at a time and put a little blue Loctite on each screw.

[GSMullins]

I swear to God, true story. I was in a shop just recently and the smith said, 'I put my lips around the gas tube and blow til I find the sweet spot (least resistance).'

The guy was an prior service old timer, obviously already set in his ways. So I didn't make fun of him, but it did take a lot to hold my composure.

Long, long time ago, back when British sports cars were still around, we used to synch carburetors with a hose held up to our ear: when one cylinder appoximated the others, it was synched. :p

Fact is, gas blocks typically have openings substantially larger than the gas port in the barrel, so there's quite a bit of leeway. I use a couple of straight edges on either side of the upper to approximate a central position, and call it good. So far, no harm..

GSM

[ace4059]

Ever tried one of these? I use the bolt on gas blocks and this product lines it up
http://www.rainierarms.com/?page=shop/detail&product_id=1089

[BrickShitHouse]

Ever tried one of these? I use the bolt on gas blocks and this product lines it up
http://www.rainierarms.com/?page=shop/detail&product_id=1089

So does this just provide dimples for the gas block screws to dig into then? Not sure how this works.

[Col_Crocs]

So does this just provide dimples for the gas block screws to dig into then? Not sure how this works.

Yes and it helps align ports as well. It has a set screw that lightly anchors against the barrel's port ensure your dimples are where they need to be for proper alignment.

[kwilkin]

This is what I do-I place a mark using a pencil on the block, indicating the center of the port and then draw a line line using a straight edge to indicate the center of the barrel's gas port, place a mark on the barrel's shoulder.


That's how I do it, too.

I didn't dimple my barrel for set screws (DD 10.3" with DD Mk12 gas block). Correspondence with DD CS indicated that dimples weren't necessary, but I do acknowledge that dimples are the best way to go.

[ace4059]

So does this just provide dimples for the gas block screws to dig into then? Not sure how this works.

It just gives you a place to drill the dimples so it all lines up.

[308sako]

I swear to God, true story. I was in a shop just recently and the smith said, 'I put my lips around the gas tube and blow til I find the sweet spot (least resistance).'

The guy was an prior service old timer, obviously already set in his ways. So I didn't make fun of him, but it did take a lot to hold my composure.

I wonder if Thursday was his day in the barrel?

Aside from that, marking the proper alignment helps considerably, and allowing the gas tube to be centered and without any strain is also an indicator. What I have not seen mentioned is that the gas block should not be in absolute contact with the barrel shoulder. A spacing of between .005" - .040" has worked for me.

[BrickShitHouse]

I'm going with your guys' recommendation and scrapping the clamp on gas block in favor of one that uses set screws.

Is making dimples on the barrel a must? If so can this be done without the use of that Rainier Arms barrel dimpler? How much do I drill into the barrel for the dimple. I imagine just a little bit to keep the screws in place.

Thanks for the help gents.

[Col_Crocs]

It's ideal. If you feel confident about aligning the gas block, you can actually just use its set screws to reference mark where you need to dimple. Just tighten it enough to dig into and mar the barrel. You dont have to drill too deep... The depth of the tip of the drill bit is what the BRDE Jig's instructions recommend. Do you have the proper tools for the job?

[Robb Jensen]

Ever tried one of these? I use the bolt on gas blocks and this product lines it up
http://www.rainierarms.com/?page=shop/detail&product_id=1089\

This works very well. I wish they made them for .625" and .875" gas block seats too.

[BrickShitHouse]

Do you have the proper tools for the job?

I have a drill and a vise. :confused:

[BrickShitHouse]

I bit the bullet and snagged a Rainier Arms Barrel Dimpler. I figured I'd might as well buy the thing and be done with it.

As far as using it goes, I don't have a drill press but i do have a drill. Could i just attach the barrel dimpler and then hold it in a vise and dimple it with the drill from there? I saw that there's flats on either side of the tool which I assume is for doing this. I tried to download the instruction manual but no dice.

[user]

Bore scope works well also if available

[wetidlerjr]

I bit the bullet and snagged a Rainier Arms Barrel Dimpler. I figured I'd might as well buy the thing and be done with it. As far as using it goes, I don't have a drill press but i do have a drill. Could i just attach the barrel dimpler and then hold it in a vise and dimple it with the drill from there? I saw that there's flats on either side of the tool which I assume is for doing this. I tried to download the instruction manual but no dice.

Try this: Rainier Arms Gas Block Barrel Dimpler (http://rainierarms.com/misc/dimple_jig.doc)

[midSCarolina]

I bit the bullet and snagged a Rainier Arms Barrel Dimpler. I figured I'd might as well buy the thing and be done with it.

As far as using it goes, I don't have a drill press but i do have a drill. Could i just attach the barrel dimpler and then hold it in a vise and dimple it with the drill from there? I saw that there's flats on either side of the tool which I assume is for doing this. I tried to download the instruction manual but no dice.

This is the text... can't get the pics but it is pretty simple. Just use calipers and make sure the dimples measure out to 11/64"

Use of the BRDE gas block dimple jig:


1. Slip the jig onto the barrel and using the pointed set screw to screw into the gas port in the barrel. The pointed set screw will self center the jig on the barrel. This screw just needs to be snugged down

2. Install the soft point set screw in the 2nd hole, this screw can be tightened down.

3. Flip the assembly over and use a 11/64" bit in a drill to start the dimples.

4. Now the jig can be removed. It can be used as a barrel holder when using the soft point screw. Pictured below is the dimples started.

5. Next the dimples are opened up. Maximum size should be the OD of the drill (11/64") and depth of the point. Less OD and depth is okay also.

6. Now the gas block can be installed on the barrel. Line up with the dimples and install one set screw with appropriate thread locker, such as Loctite 272. Snug up. Install the second set screw and snug up. Torque the screws to the manufactures specifications.


**Note: due to manufacturing variations, the gas block may appear slightly canted when assembled under a handguard. I have found that this is typically caused by slop between the upper and alignment pin.

[purehavoc]

I draw a line down the barrel for center , the hole in most gas blocks are alot bigger than the hole in the barrel so you will have some variance if its off a little . I dont dimple my barrels , I tighten the set screws and loosen about 4 or 5 times to make sure I get good contact on the barrel which does dig in pretty well then I stake the gas block against the set screws so I dont have to worry about them backing out .