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poimen
15 May 2017, 10:27
how important is it to have a dimpled barrel for indexing purposes? and if your barrel isn't dimpled, and you add a non pinned gas block, how likely is the gas block to come loose? for that matter, what is the best way to attach a gas block that has the 2 set screws on the bottom without a pre-dimpled barrel?

Stone
15 May 2017, 13:01
The dimples aren't for indexing but help to hold the gas block in place in case it gets bumped or the rifle takes a tumble. Depends what you are doing with the rifle, if its a range plinker and your rail covers the gas block you will be fine without dimpling or pinning. Just make sure you Loctite the set screws. If you think you will defend your home or life with it get it pinned. All of my rifles are dimpled and pinned. I have the jigs from BRD engineering. As far as lining up the gas block, just put a witness mark on the block and one on the barrel. Line them up and tighten down the screws and you will be GTG.

Aberration79
15 May 2017, 13:01
I could be wrong but I think the dimpling has more to do with better securing the gas block than indexing. I bought a dimpling jig so I could dimple my barrels.

poimen
15 May 2017, 13:04
The dimples aren't for indexing but help to hold the gas block in place in case it gets bumped or the rifle takes a tumble. Depends what you are doing with the rifle, if its a range plinker and your rail covers the gas block you will be fine without dimpling or pinning. Just make sure you Loctite the set screws. If you think you will defend your home or life with it get it pinned. All of my rifles are dimpled and pinned. I have the jigs from BRD engineering. As far as lining up the gas block, just put a witness mark on the block and one on the barrel. Line them up and tighten down the screws and you will be GTG.

Thanks for the info! I might just pay the extra $40 from BA and have them pin a block on for me. Haha.


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Stone
15 May 2017, 13:08
That's what I would do, pinning it makes it rock solid. I use their gas blocks, good stuff.

alamo5000
15 May 2017, 18:50
how important is it to have a dimpled barrel for indexing purposes? and if your barrel isn't dimpled, and you add a non pinned gas block, how likely is the gas block to come loose? for that matter, what is the best way to attach a gas block that has the 2 set screws on the bottom without a pre-dimpled barrel?

I would definitely recommend at minimum dimpling the barrels. It's not hard to do. Many companies make simple jigs to do it. When I bought my rail and other components from SLR they actually offered to dimple my barrel for me (it was a ballistics advantage barrel).

Pinned is superior but dimpled is sufficient for recreational shooting provided everything is done right. None of mine are pinned (yet) but I have only had a problem once where my gas block came loose and that was because everything wasn't tightened down properly and loctited into place. It was a very simple fix but the point is that it did come loose.

No dimple for me would be not a good idea.

Dimple is sufficient for most average shooters considering that you use loctite or some other form of thread locker. A single shot might not cause problems but repeated fire could rattle the screws loose.

Pinned is the best but not as easy to accomplish without a gunsmith to help out.

UWone77
16 May 2017, 00:26
Thanks for the info! I might just pay the extra $40 from BA and have them pin a block on for me. Haha.


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You won't find anyone doing it cheaper (pinning), which is why BA is always a fantastic option.

BoilerUp
16 May 2017, 06:11
$30 for a jig: http://slrrifleworks.com/index.php?route=product/product&product_id=579

poimen
16 May 2017, 06:14
$30 for a jig: http://slrrifleworks.com/index.php?route=product/product&product_id=579

Haha maybe for my next one, for now, I think this is best left to a professional. Lol


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alamo5000
16 May 2017, 07:37
Haha maybe for my next one, for now, I think this is best left to a professional. Lol


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Good thought process [:D] Some things are easy to do yourself but other things are best left to the pros.

I am also with UW on this one. If BA will pin the block for you you will be good to go. That's the best route.

If you are going M-Lok though whatever your rail choice is you might want to make sure to check the inner diameter of the rail. For example SLR has very slim rails and with a full size gas block it can cause binding of mlok accessories up around your gas block. Don't freak out too much about it but it is a known flaw when all the stars align with the right components to make it happen.

poimen
16 May 2017, 07:44
Good thought process [:D]
If you are going M-Lok though whatever your rail choice is you might want to make sure to check the inner diameter of the rail. For example SLR has very slim rails and with a full size gas block it can cause binding of mlok accessories up around your gas block. Don't freak out too much about it but it is a known flaw when all the stars align with the right components to make it happen.

Thanks for the tip! I think I'm gonna end up going with the aero gen 2 quantum. It uses that BAR barrel but which looks like it makes the handguard a little wider than most. I think it should be alright.


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mustangfreek
16 May 2017, 08:06
$30 for a jig: http://slrrifleworks.com/index.php?route=product/product&product_id=579

Ya I've seen these and the poplar BRD kits..I've always wanted to take a gas block and make my own, but haven't yet..lol..I'm ginger stubborn

JoshAston
16 May 2017, 09:28
The dimple is solely for indexing. Any force strong enough to remove a set screw gas block isn't going to care about whether or not it's dimpled.

UWone77
16 May 2017, 13:52
The dimple is solely for indexing. Any force strong enough to remove a set screw gas block isn't going to care about whether or not it's dimpled.

Exactly.

This is why I'm like... why do people double dimple.... eh. I've seen several manufacturers do this.

Stone
16 May 2017, 19:48
The dimple is solely for indexing. Any force strong enough to remove a set screw gas block isn't going to care about whether or not it's dimpled.

The dimple is irrelevant to indexing, that's like saying you need the dimple to index. A properly lined up gas block is achieved whether it is dimpled or not. On a non dimpled barrel the set screw contact is decreased and there is no way to achieve the torque needed to bite in deep enough to prevent it from moving if bumped with force. A light tap with a hammer on a non dimpled barrel will move it. Now sink that set screw into a hole and you have increased its holding power three fold if not more. Simple physics, resistance.

Non dimpled- Worst
Dimpled- Better
Pinned- Best

BoilerUp
16 May 2017, 21:02
The dimple is irrelevant to indexing, that's like saying you need the dimple to index.

No, it's not "like" saying that at all. A properly dimpled barrel simplifies indexing a set screw gas block as you simply have to index the rear set screw. Of course, a dimple is useless if you are pinning or using a clamp on gas block.

I do agree that a dimple will improve the mounting of a set screw gas block, but a properly torqued set screw gas block on a non-dimpled barrel isn't going anywhere under normal use and if you've got it tucked under a handguard then you'd have to be doing something pretty weird to knock it out of alignment.

Axlnut
16 May 2017, 22:31
A lot of posters are discussing dimples/set screws and taper/straight pins like they are mutually exclusive and that is not the case.

Set screws into a dimpled barrel are far stronger than set screws biting into a non-dimpled barrel, and don't require as much torque on the small fasteners to be effective. I don't want to oversimplify and say it's common sense.. but it is.

A pinned gas block (aside from fixed FSB) in the AR world is typically also dimpled, and this is an area where the MECHANICAL indexing of the set screw becomes hugely beneficial - that's the word missing... mechanical indexing. You can index anything, and hope it stays indexed through the next operations (pinning, etc) but when you mechanically index via a set screw, then set up a rigid fixture for pinning.. nothing can move, life is good. After pinning you can do whatever you want with the set screw, leave it, remove it, etc.

An example that almost everyone knows well where there is no mechanical index prior to pinning: AK platform.

Google search "AK canted fsb" and check how easy they are to get straight with no mechanical index (based off the gas port location).

Dimples and set screws are fine, 1 or 2. Slather everything in loctite and it's likely never going anywhere.

Pinned is fantastic. Pinning without dimples and set screws is a royal PITA to jig up.

No dimples, no pins.. meh. Lazy. The hole is already in the gas block by default, take advantage of it.

Stone
17 May 2017, 06:15
No, it's not "like" saying that at all. A properly dimpled barrel simplifies indexing a set screw gas block as you simply have to index the rear set screw. Of course, a dimple is useless if you are pinning or using a clamp on gas block.

I do agree that a dimple will improve the mounting of a set screw gas block, but a properly torqued set screw gas block on a non-dimpled barrel isn't going anywhere under normal use and if you've got it tucked under a handguard then you'd have to be doing something pretty weird to knock it out of alignment.

Agreed, "A properly dimpled barrel simplifies indexing" But the other post said it was "solely for indexing" Implying that indexing couldn't be achieved without dimpling. Which is what I got from reading it. Besides it being a direct contradiction to my original post I felt I needed to defend my statements. Its all good. I think we are, for the most, debating towards the same end result. In my mind I saw a gas block exposed past the rail which kind of tied into my original post which is what I was alluding to. I failed to mention that in the last post. I dimple before pinning as well which holds the block in place so I know nothing will shift while going through the pinning process.

JoshAston
17 May 2017, 10:34
Agreed, "A properly dimpled barrel simplifies indexing" But the other post said it was "solely for indexing" Implying that indexing couldn't be achieved without dimpling. Which is what I got from reading it.

I didn't say indexing can't be achieved without dimpling. But the reason for dimpling is most definitely to simplify indexing.

alamo5000
17 May 2017, 11:56
Alright alright! It's used for indexing! [BD]

My opinion on it is yes that's 100% correct but it does also allow the set screws more territory to bite into. But if those set screws are not loctited or whatever into place repeated fire and recoil (not brute force directly on the block) can rattle those screws loose. Dimple or no dimple if the screws back out the block comes loose.

Everyone though seems to be in agreement that pinning is sure fire though. [:D]

BoilerUp
17 May 2017, 19:24
Alright alright! It's used for indexing! [BD]

My opinion on it is yes that's 100% correct but it does also allow the set screws more territory to bite into. But if those set screws are not loctited or whatever into place repeated fire and recoil (not brute force directly on the block) can rattle those screws loose. Dimple or no dimple if the screws back out the block comes loose.

Everyone though seems to be in agreement that pinning is sure fire though. [:D]

Yeah, but do you loctite the cross pin? :P

cjd3
17 May 2017, 19:30
Yeah, but do you loctite the cross pin? :P
Hell no, Rocksett.

Stone
17 May 2017, 19:43
Just arc weld it...

din
17 May 2017, 20:26
Not dimpling will get you killed on the streets.

doubletap
21 May 2017, 04:42
So I see some barrels offered with the gas block pinned on. Do they come with the gas block attached and you have to knock the pin out, install the barrel nut and out the block back in or do they come with the barrel drilled for the pin and you put the barrel nut on the the gas block and put the pin in?
The reason I ask is because I've read the pins can be a bear to take out.

BoilerUp
21 May 2017, 06:29
So I see some barrels offered with the gas block pinned on. Do they come with the gas block attached and you have to knock the pin out, install the barrel nut and out the block back in or do they come with the barrel drilled for the pin and you put the barrel nut on the the gas block and put the pin in?
The reason I ask is because I've read the pins can be a bear to take out.

For BA it comes installed so you have to knock the pin out to remove the block to install the barrel nut. It's not that difficult assuming you have the right tools.

fledge
21 May 2017, 11:56
My latest BA barrels did not have the pin installed. It came in a separate bag.


Removing pins is not as difficult as installing. You don't need a starter punch. :)

BoilerUp
21 May 2017, 12:22
My latest BA barrels did not have the pin installed. It came in a separate bag.


Removing pins is not as difficult as installing. You don't need a starter punch. :)

They must have gotten tired of getting calls from newbs asking how you get the barrel nut installed on a barrel with a pinned gas block