Dimple Barrel - AR15.COM

AR-15 » Build It Yourself

AR Sponsor:

Posted: 9/21/2017 6:24:37 AM EDT

OK be easy on me.... Do you really need to dimple your barrel for the gas block? I have a Stag Arms Mod 3 and it is not dimpled. I know some barrels come already dimpled. But the one I just revived from Primary Arms is not. It makes sense to be dimpled but do you really need to?

Thanks

HDHP

Posted: 9/21/2017 6:43:37 AM EDT

[#1]

Dimpling the barrel adds another layer of security, but it isn't absolutely necessary.

Check to see that the bottom of the grub screws in the gas block have a "cupped" surface. This is what bites into the barrel steel to prevent shifting.

If you want, you can add loctite between the block and barrel and on the screw threads.

Posted: 9/21/2017 6:43:48 AM EDT

[#2]

Not everyone does.

Posted: 9/21/2017 6:51:01 AM EDT

[#3]

OK, thanks, Guys! I do have Blue Loctite on the threads. The gas block is aluminum and I seen red Loctite rip the threads out before.

Thanks

HDHP

Posted: 9/21/2017 6:09:08 PM EDT

[#4]

I would take the time to dimple the barrel and do it right. It is very easy to dimple it.

Posted: 9/21/2017 7:43:13 PM EDT

[#5]

I don't and I have not had one come loose yet.

Posted: 9/21/2017 8:04:37 PM EDT

[#6]

Only useful for making sure it's lined up but even then it's not necessary

Posted: 9/21/2017 8:21:19 PM EDT

[#7]

Quote History

Quoted:
Only useful for making sure it's lined up but even then it's not necessary

View Quote

So if it is basically unnecessary per your opinion, then why do manufacturers such as BCM, do it?

Posted: 9/21/2017 8:22:34 PM EDT

[#8]

Quote History

Quoted:
Only useful for making sure it's lined up but even then it's not necessary

View Quote

This. Using a dimpling jig allows you to provide an indexing dimple on the bottom of the barrel to ensure the gas port in the block is aligned with the barrel's port.

Does a dimple help keep a gas block in place? I dunno. But since I can't see a way most gas blocks (NOT FSBs) could be moved or displaced, I don't know of a way to really test that question.

Posted: 9/21/2017 8:45:30 PM EDT

[#9]

Quote History

Quoted:

So if it is basically unnecessary per your opinion, then why do manufacturers such as BCM, do it?

View Quote

Probably best to ask them as what any of us say, would simply be a guess as to why they have chose to do something a certain way.

Posted: 9/22/2017 12:13:57 AM EDT

[#10]

Well, I did not and the darned thing walked forward just afterI had gotten the gas block dialed in.
The screws were tight and Thread Locked.
I'm going to dimple the barrel now.

10.5" 300 AAC pistol, BTW.

Posted: 9/22/2017 9:41:01 AM EDT

[#11]

I have not dimpled any of the barrels I have built rifles out of and have built probably a dozen that way. None of the rifles I have built have had any movement of the gas block. I would suggest you use a steel gas block as aposed to an aluminum one. Also, to line up the gas holes I use a standard #2 pencil.

Posted: 9/22/2017 12:17:23 PM EDT

[#12]

Quote History

Quoted:

So if it is basically unnecessary per your opinion, then why do manufacturers such as BCM, do it?

View Quote

Probably to speed up the assembly line and eliminate problems with misaligned gas blocks

Posted: 10/1/2017 11:33:42 PM EDT

[#13]

No need to dimple if the gas block is going to end up covered by a rail. The set screws should have concave tips that spread out when torqued. Blue Loctite, if you must. Do not use red on set screws that small.

Posted: 10/2/2017 12:32:12 AM EDT

[#14]

Quote History

Quoted: Also, to line up the gas holes I use a standard #2 pencil.

View Quote

I'm trying to picture this. Would you be willing to elaborate? I just eyeball it from various angles and haven't had any problems but, I'm down for more precision.

Posted: 10/2/2017 11:46:03 AM EDT

[#15]

I didn't worry about it on mine. I have seen setscrews hold stuff that goes trough a lot more heat and abuse than a gas block would ever see. I tightened and loosened mine several times so the dimple on the setscrews could bite in really good and then I just used blue locktite. No issues.

If it makes you feel better to have them, then go for it. It wont hurt anything.

Posted: 10/2/2017 9:07:46 PM EDT

[#16]

Quote History

Quoted:
I'm trying to picture this. Would you be willing to elaborate? I just eyeball it from various angles and haven't had any problems but, I'm down for more precision.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted: Also, to line up the gas holes I use a standard #2 pencil.

I'm trying to picture this. Would you be willing to elaborate? I just eyeball it from various angles and haven't had any problems but, I'm down for more precision.

One method is to make a line on the barrel with that #2 pencil through the center of the gas port and similarly mark the gas block for center. After that, you need to also line up the port and the gas block along the length of the barrel. This takes a little measurement and some patience, but it works.

After you go through the steps for this process, you start to figure out why a production shop dimples their barrels: it is a lot faster to do than setting up a ton of marks and verifying that they're all spot on.

Posted: 10/2/2017 11:07:21 PM EDT

[#17]

Quote History

Quoted:
Well, I did not and the darned thing walked forward just afterI had gotten the gas block dialed in.
The screws were tight and Thread Locked.
I'm going to dimple the barrel now.

10.5" 300 AAC pistol, BTW.

View Quote

This is surprising to me. I swapped a railed GB for a low pro GB that I had on a carbine and the tips of the set screws had cut little rings in the barrel surface and no way it could have walked. Were your set screws hardened? Is the GB steel or aluminum?

Posted: 10/3/2017 4:40:12 AM EDT

[#18]

Quote History

Quoted:
This is surprising to me. I swapped a railed GB for a low pro GB that I had on a carbine and the tips of the set screws had cut little rings in the barrel surface and no way it could have walked. Were your set screws hardened? Is the GB steel or aluminum?

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
Well, I did not and the darned thing walked forward just afterI had gotten the gas block dialed in.
The screws were tight and Thread Locked.
I'm going to dimple the barrel now.

10.5" 300 AAC pistol, BTW.

This is surprising to me. I swapped a railed GB for a low pro GB that I had on a carbine and the tips of the set screws had cut little rings in the barrel surface and no way it could have walked. Were your set screws hardened? Is the GB steel or aluminum?

GB is steel. I don't know if the screws are hardened as they did leave marks on the barrel, but did not cut in. My barrel is melonited so I don't know if that made a difference.
First one I ever had walk.

Posted: 10/9/2017 10:43:15 PM EDT

[#19]

Call me crazy, but I dimple AND pin (actually I have one that's NOT dimpled, but still pinned). Dimpling, for me, it to make sure I get EXACT center. Then I pin those suckers on (and sleep like a baby because of it

).

Posted: 10/9/2017 11:03:06 PM EDT

[#20]

Quote History

Quoted:

So if it is basically unnecessary per your opinion, then why do manufacturers such as BCM, do it?

View Quote

I have BCM uppers from back in their early days that are not dimpled. They've held up just fine for years and LOTS of rounds. I also have a few builds of my own from before it was common practice to do this (ever) and they, too, are fine.

It is preferred, but not necessary. I believe most do it for simplicity when it comes to installing the block. If it was for outright reliability the blocks would be pinned.

Posted: 10/11/2017 9:48:42 PM EDT

[#21]

Quote History

Quoted:
One method is to make a line on the barrel with that #2 pencil through the center of the gas port and similarly mark the gas block for center. After that, you need to also line up the port and the gas block along the length of the barrel. This takes a little measurement and some patience, but it works.

After you go through the steps for this process, you start to figure out why a production shop dimples their barrels: it is a lot faster to do than setting up a ton of marks and verifying that they're all spot on.

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted: Also, to line up the gas holes I use a standard #2 pencil.

I'm trying to picture this. Would you be willing to elaborate? I just eyeball it from various angles and haven't had any problems but, I'm down for more precision.

One method is to make a line on the barrel with that #2 pencil through the center of the gas port and similarly mark the gas block for center. After that, you need to also line up the port and the gas block along the length of the barrel. This takes a little measurement and some patience, but it works.

After you go through the steps for this process, you start to figure out why a production shop dimples their barrels: it is a lot faster to do than setting up a ton of marks and verifying that they're all spot on.

In addition to drawing the center-line, I take the set screw completely out, turn the gas block upside down and line up the gas port in the center of the set screw hole. Then use a feeler gauge to determine the gap to the gas block shoulder or trace the front edge of the gas block so you know how far back to install it and keep the port centered.

Posted: 10/12/2017 6:51:15 PM EDT

[#22]

Quote History

Quoted:

In addition to drawing the center-line, I take the set screw completely out, turn the gas block upside down and line up the gas port in the center of the set screw hole. Then use a feeler gauge to determine the gap to the gas block shoulder or trace the front edge of the gas block so you know how far back to install it and keep the port centered.

View Quote

Doing one barrel like that, now and then, is really only a chore. But I am the type of person who can mess it up unless I pay more attention than I usually can manage, so I’m going to buy a jig before I do my next gas block.

Posted: 10/13/2017 8:35:18 AM EDT

[#23]

Quote History

Quoted:
This is surprising to me. I swapped a railed GB for a low pro GB that I had on a carbine and the tips of the set screws had cut little rings in the barrel surface and no way it could have walked. Were your set screws hardened? Is the GB steel or aluminum?

View Quote View All Quotes

View All Quotes

Quote History

Quoted:

Quoted:
Well, I did not and the darned thing walked forward just afterI had gotten the gas block dialed in.
The screws were tight and Thread Locked.
I'm going to dimple the barrel now.

10.5" 300 AAC pistol, BTW.

This is surprising to me. I swapped a railed GB for a low pro GB that I had on a carbine and the tips of the set screws had cut little rings in the barrel surface and no way it could have walked. Were your set screws hardened? Is the GB steel or aluminum?

Did it actual walk or get pushed by the bcg key from slight misalignment?

Posted: 10/13/2017 9:10:43 AM EDT

[#24]

Isn't it hard to drill or dimple a melonite type barrel?

Posted: 10/13/2017 9:40:34 AM EDT

[#25]

Quote History

Quoted:
Isn't it hard to drill or dimple a melonite type barrel?

View Quote

No. That is myth. It is surface hardened. Only a few thousandths deep. A fresh, sharp bit with a drop or two of cutting oil will cut through easily. Best to do this in a drill press to keep the bit from walking. Go very slow and let the bit do the work.

I don't dimple barrels for low pro blocks, honestly, but have pinned virgin FSBs to nitride barrels with no problem.

Posted: 10/27/2017 8:44:48 AM EDT

[#26]

For me I learned a long time ago, buy a good quality gas block with two set screws. I only use YHM gas blocks. Yes, we can buy cheaper ones but
in gas blocks and barrels, please spend a little more money for a good quality one and you will be far ahead. Problems with our personal safety devices
are not what we want. Keep shooting, have fun.

Posted: 10/27/2017 9:02:34 AM EDT

[#27]

I usually dimple barrels if they aren't already dimpled, just for my own piece of mind. I'd say it's more critical on a piston gun.
I've got a couple clamp-on gas blocks as well that have never given me trouble.

Posted: 10/27/2017 3:57:46 PM EDT

[#28]

Quote History

Quoted:

No. That is myth. It is surface hardened. Only a few thousandths deep. A fresh, sharp bit with a drop or two of cutting oil will cut through easily. Best to do this in a drill press to keep the bit from walking. Go very slow and let the bit do the work.

I don't dimple barrels for low pro blocks, honestly, but have pinned virgin FSBs to nitride barrels with no problem.

View Quote

You are obviously better at it than I am. I get maybe 3-5 dimples from a carbide tipped drill bit when dimpling a nitride barrrl. After that, all it does is mark the barrel but will not drill into it. I went ahead and bought a solid carbide drill bit for $20 and it works so much better. I have dimpled 18-20 barrels so far.

It's not needed but it aligns the GB perfectly and it adds a tiny bit of extra security. I don't do real ninja covert ops stuff so all my barrels should be fine not being dimpled.

Posted: 10/27/2017 5:01:11 PM EDT

[#29]

If a barrel isn't dimpled, I prefer to do so because the amount of surface area the set screw contacts is greater than if you don't.

I always put blue loctite on the screws.

Another thing to consider is when you put your gas block on the barrel, I like to have at least a little bit of resistance so that there is better sealing and contact. You want the gas block to remain where it is, so any amount of friction installing it won't hurt.

Posted: 10/31/2017 1:57:25 AM EDT

[#30]

Quote History

Quoted:
Dimpling the barrel adds another layer of security, but it isn't absolutely necessary.

Check to see that the bottom of the grub screws in the gas block have a "cupped" surface. This is what bites into the barrel steel to prevent shifting.

If you want, you can add loctite between the block and barrel and on the screw threads.

View Quote

The above is an excellent answer to the OP's question. I would only add that dimpling ensures a nearly perfect
alignment of the Gas Block and Barrel gas holes, i.e, no measuring and guess work.

[ARCHIVED THREAD] - Dimple Barrel

AR-15 » Build It Yourself

AR Sponsor:

Warning

Confirm Action

About AR15.COM

Stay Connected

Newsletter

Contact Us