Gunsmithing 8. HOW-TO: Ultimate AR Adjustable Gas Block

Hellbender

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Part 8:

For those that use the JP Adjustable Gas Blocks (& some other brands), I don't like the single set screw that is supposed to be secured with Locktite (which breaks down under high heat, like a gas block).

So I add an extra set screw that locks the gas adjustment screw...

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PS: I also always use a CLAMP on style gas block in a small (.750" or smaller dia.) barrel, as I've heard of the set screw type actually deforming the bore of the barrel when tightened.
 

AXEMAN

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Re: 8. HOW-TO: Ultimate AR Adjustable Gas Block

nice mod. i am getting a PRI gas block. makes me wonder just how adjustable it is when they advise using loctite on the screw.
 

Hellbender

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Re: 8. HOW-TO: Ultimate AR Adjustable Gas Block

Axeman...

If you are building a precision AR, I would look at some of the clamp on blocks, instead of the setscrew type.

They WILL deform the bore, no way around it....... if it's enough to matter, I can't say, but I like to remove all the question marks I can.
 

Hellbender

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Re: 8. HOW-TO: Ultimate AR Adjustable Gas Block

JP makes several models, and there's another knock off of the JP aluminum railed model, but I can't remember who makes it.
 

dmg308

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Re: 8. HOW-TO: Ultimate AR Adjustable Gas Block

I drill taper pins on all gas blocks no better way IMO.Your set screw mod is a good step.
 

Hellbender

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Re: 8. HOW-TO: Ultimate AR Adjustable Gas Block

dmg308...

On a combat gun, I agree, nothing is better than taper pins.

But, this is a match gun only and will probably be apart many times in it's life, new barrel once a year, etc, etc.

And, from an engineering standpoint, for PURE accuracy, the pins WILL deform the bore slightly.....again, no-one MAY ever be able to tell, but a question mark none the less.
 

dighawaii

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Re: 8. HOW-TO: Ultimate AR Adjustable Gas Block

What an excellent idea you have. I wished my JP Precision gas block came with a set screw. It would have saved me from going to the local hardware store to get a replacement.
 

pappy42

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Re: 8. HOW-TO: Ultimate AR Adjustable Gas Block

Some high dollar barrel providers dimple barrels for set screw retained type gas bock. I think that they wouldn't do that if they thought the set screw(s) would deform the bore and cause accuracy problems.

I do like the the set screw mod for the gas adjusting screw.
 

Hellbender

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Re: 8. HOW-TO: Ultimate AR Adjustable Gas Block

Pappy42--

Honestly, on a normal bull barreled gun with the larger dia. (OVER .750") gas block boss, it would probably never deform enough to matter, but why have a question mark on a $600+ Kreiger barrel? The more of these question marks I can remove, the better I like it.