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Justintoxicated

.936 Adjustable Gas Block and Extended Length handguard?

37 posts in this topic

So I'm looking for .936 adjustable gasblock, but I also want an extended length handguard / float tube.  Are there any combos where I can put the gasblock under the handguard and still have access to adjust it?  I was thinking to go with the JP Modual handguard and JP low profile adjustable gas block but I don't know how well this will work out.  JP said it would work, but the email was really brief and I'm having my doubts.

This is the barrel I will be using and I'm not sure if it is dimpled for the gas block. (Hoping it is a good one, it does not say that it is rifle cut or hand lapped, so I'm hoping I'm not making a mistake).  I had ordered a custom barrel but I will probably cancel that for now.

http://www.rainierarms.com/?page=shop/detail&product_id=2233

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Considering the handguard and gas block you're looking at - they're both made by the same manufacturer, and that manufacturer says they'll work together.  I think I'd trust the manufacturer of those parts, about their compatibility.  <dontknow>

If they don't work together, you've always got this going for you - there's only one place to contact about the problem.  <thumbsup> ;D

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is the JP classic FF tube any good or is it a pain to install?  I got their new rapid configuration one and it has a nice barrel nut system on it, but the classic modular one seems like it might be more difficult?  Of course they don't make the rapid config one for LR308. I read something about having to loctite the barrel nut and wait for it to dry as part of the install process.  Which has me a little worried about someday having to remove it to change barrels.

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the barrel nut threads into another piece that gets locktighted to the receiver threads. so changing a barrel will be no prob. if the other piece ever needs too come off the receiver a heat gun and a few minutes would be all it takes. i can adjust my gas block through the slots in the hand guard. as for the gas block i think all jps are clamp on, so you dont have to dimple the barrel

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the barrel nut threads into another piece that gets locktighted to the receiver threads. so changing a barrel will be no prob. if the other piece ever needs too come off the receiver a heat gun and a few minutes would be all it takes. i can adjust my gas block through the slots in the hand guard. as for the gas block i think all jps are clamp on, so you dont have to dimple the barrel

So you used red lock-tight and could still remove it?  You didn't have any problems with the outer piece slipping? 

Is there by chance a similar tube that has a better barrel nut assembly? 

It seems kinda complicated, or harder to adjust, compared to their new tubes.

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the outer piece gets the red locktite the inn barrell nut gets anti siezeed the only reason you would have to remove the outer piece is if you were changing to a different hand guard. the reason for the locktite is to keep the outer piece in position for torqueing the barrel nut. after that the torque is what would keep it all in place. you locktite the outer barrel nut to the receiver and let it set up over night. then install the barrel and tighten the inner nut. takes no time at all.

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I'm going to step in here and say that I personally feel red loctite might be a mistake. I personally would use blue.

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the outer piece gets the red locktite the inn barrell nut gets anti siezeed the only reason you would have to remove the outer piece is if you were changing to a different hand guard. the reason for the locktite is to keep the outer piece in position for torqueing the barrel nut. after that the torque is what would keep it all in place. you locktite the outer barrel nut to the receiver and let it set up over night. then install the barrel and tighten the inner nut. takes no time at all.

So the only thing that prevents the outer piece from turning while you potentially torque the piss out of the barrel nut is the lock-tight?  Seems like a screwy design to me.

I'm quickly finding out that all other 15" free float tubes I find are only clamp on style, which does not seem like a great design to me at all for a tube that is 15" long, and/or I would still have the issue of being able to reach the adjustable gas block without removing the handguard.

What do you guys think about the JD handguard in comparison?

http://www.jdmachinetech.com/merchant2/merchant.mvc?Store_Code=JD&Screen=PROD&Category_Code=223RL&Product_Code=223CHG

And the barrel nut:

http://www.calguns.net/calgunforum/showthread.php?t=435301

I would probably have to drill a hole in the tube to access the adjustable gas block though. 

I can't find a forward facing adjustment screw gas block in .936 :(

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the jp is exactly the same setup as the jd machine they just recomend using the locktight vs a piece of gas tube, but the inner and outer nut setup is the same.

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the jp is exactly the same setup as the jd machine they just recomend using the locktight vs a piece of gas tube, but the inner and outer nut setup is the same.

The gas tube tool isn't to hold the outer nut in place, it is to line up the gas tube.  I usually just use a drill bit that is the same diameter.

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I would probably have to drill a hole in the tube to access the adjustable gas block though. 

No big deal. I did that for a Troy TRX rail that I have on one of my AR-10's with a PRI lo-pro adjustable blocks. With a little touch-up....no one will ever even notice it at a glance.

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PRI.

Precision Reflex.

This one?

http://www.precisionreflex.com/Detail.aspx?PROD=186815&CAT=4274

Will it fit under the Apex handguard?  I'm guessing not since that would be nice :(

I'm leaning towards the Apex handguard now, I don't like that it is "clamp on style" but it seems better than relying on a bunch of lock-tight.  Not sure which Rail height I would need since I'm not attaching to a DPMS Receiver.  It will be going on a JD Machine receiver if anyone knows how that compares.

I didn't think picking a handguard and gas block would be so difficult.  Definitely very limited compared to the stuff out there for AR-15's.

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well, if you go with a non-floating handguard, theres no issue, but the gas block will be visible

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This one?

http://www.precisionreflex.com/Detail.aspx?PROD=186815&CAT=4274

Will it fit under the Apex handguard?  I'm guessing not since that would be nice :(

It should fit.

Not sure which Rail height I would need since I'm not attaching to a DPMS Receiver.  It will be going on a JD Machine receiver if anyone knows how that compares.

I think that JD is still gonna be the SR25/DPMS pattern.

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You'll have to do one of two things - measure it, or call JD and ask them.

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You'll have to do one of two things - measure it, or call JD and ask them.

lol @ call JD, they haven't been taking phone calls in months.

not sure how to measure it otherwise since it wants to measure from the center of barrel... Oh well not like I can get this handguard or gas blocks right now anyways....

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lol @ call JD, they haven't been taking phone calls in months.

Sure, they take calls.  Talked to them a week and a half ago, about the timeline between ordering and shipping for the 308 matched upper/lower.  Their answer was:  Every order placed right now will be ready to ship somewhere between 3 and 4 months.

They'll answer, you just need to be persistant.  I got through the first try.

There's a thread pinned in the DPMS section that tells you how/what to measure. 

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I've got a PRI adjustable gas block mounted to a 300blk barrel (.750" I think), and it's under a 12.5" Apex FF tube. Mine is the old style tube made when they had a smaller tube for small platform than large. I can't guarantee it but it looks to me like there is enough room under mine (which is smaller than the present ones) to mount a low pro PRI adjustable .936". I don't know if you expect to be needing to adjust the GB on a regular basis, but on mine, since the Apex tube mounts to tha barrel nut mount with 4 radially located bolts, I took the tube off while I adjusted the gas impulse to cycle my lightened bcg, and once it was set I bolted the tube on. If you expect to be adjusting it regularly, and don't want to remove the tube, You will probably need to make access port on the side of the FF tube.

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I've got a PRI adjustable gas block mounted to a 300blk barrel (.750" I think), and it's under a 12.5" Apex FF tube. Mine is the old style tube made when they had a smaller tube for small platform than large. I can't guarantee it but it looks to me like there is enough room under mine (which is smaller than the present ones) to mount a low pro PRI adjustable .936". I don't know if you expect to be needing to adjust the GB on a regular basis, but on mine, since the Apex tube mounts to tha barrel nut mount with 4 radially located bolts, I took the tube off while I adjusted the gas impulse to cycle my lightened bcg, and once it was set I bolted the tube on. If you expect to be adjusting it regularly, and don't want to remove the tube, You will probably need to make access port on the side of the FF tube.

JP: Minimum recommended tube ID 1.750” (allows min .050” clearance on all sides)

JP Block is .770" tall over bore. 

Then the PRI block is .780 tall over bore, and that should allow .040 clearance on the top but that exceeds the minimum specified by JP.  I'm not sure how much this will matter?

I'm also not sure which is a better block.  I know some say to get steel over aluminum, and other say to get a clamp on over a set screw type. I would imagine the clamp on will be better despite the material if the barrel has no divots in it.  I'm not sure the JP block even qualifies as a clamp style though, I think it also required the divots.

I'm also confused why the PRI requires a straight gas tube and the JP makes no mention of this.  They are both a similar height over bore!?

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You don't have to have divots in the barrel to use a set-screw gas block.  The tips of the set screws will bite into the barrel just fine.  If you absolutely don't feel like the setup is secure enough, it's easy to drill your own.  Very easy.  They're not necessary, in the least, though.

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Not looking to add confusion here, but I've heard two schools of though on the aluminum /steel issue. Aluminum expands at a different rate than steel, I prefer to use a steel, but many are using the aluminum JP's so they must work OK. Another debate is the clamp vs setscrew. I have read that you ideally don't want to make a localized point of pressure on your barrel if you can help it, either with tightening the two set screws too much or tightening the clamp too much. I like to dimple the barrel slightly, make sure I have a snug GB barrel fit and just tighten the set screws enough to snug (with locktite).

I don't know if it really makes that much difference. I also don't know if the aluminum blocks are susceptible to erosion because I have used the steels exclusivly.

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I can see your point. But I don't think that I'd worry about erosion........unless you shoot the living hell outta the thing. And even then.....gas blocks are like brake pads on a car. They're easy and fast to swap out.

Just thinkin out loud (for what it's worth).

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