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MGI Adjustable Gas Tube


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Do you mind me asking what handguard your going with?  I recently built an AR 15 where I used the old style Apex hand guard, which is one of the smallest dia handguards I know of, along with the PRI adjustable lo pro gas block. Although I built a 15, and the GB I used was the .750" bore model, I can't think of any other adjustable gas block that is as small as the PRI. The one I used was identical in size to the standard lo pro GB's offered by Vltor, Troy and others, with the exception of the small adjustment screw on the right side.

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You said that they told you that their low pro gb won't work with their ff tube. If anyone would know, I guess it would be them. Couldn't they suggest a lo pro gb that would fit, even a non adjustable? I'm wondering if the reason that they told you it wouldn't work, was because there was no access to the adjustment screw. If that was the case, you could remedy the problem by making a small hole in the side of the tube. I'm thinking, that there must be some gb that should fit under the handguard, No? If so what other gas block could possibly be smaller. Maybe the issue is one of installation, or adjustment access, I'd be interested to hear how you resolve the problem, as I was thinking about trying one of their hand guards myself.

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Here is the text from my question to them:

Will this:

875 (308) Low Pro Adj. Gas Blk W/ Straight Gas Tube

Fit under this:

Gen III SR25/DPMS 308 15" Carbon Fiber Forearm Black


And their response:


It will not fit, it rubs on the top rails mounting bar.

Tony Holdren

Precision Reflex Inc (PRi)

Sales & Marketing Manager

710 Streine Dr.

New Bremen, Ohio 45869

Maybe because I have to use a .875 gas block?

That's why I was looking at the adjustable gas tube.   

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First off don't take any of this as me being argumentative, I'm just trying to educate myself here, and maybe benefit some of the other members in the process. Since I've never actually handled one of their handguards and haven't looked down the barrel to see how much clearance they have, I'm working at a disadvantage. I have installed several gas blocks and tubes in several different AR's. I've installed .750 and .936" ones. The way I figure it, The location of the gas tube hole above bore centerline on the uppers  of the AR's should be petty much the same , with the AR 15 platform being one measurement and the 7.62 AR being another, If that is not the case wouldn't you need different height gas spigots on the BC's to accommodate the difference? So presuming that the .308 AR gas tube hole is the same height above the bore center. The difference between a .750" and a .875 or .936" GB should basically be in the bore of the GB to accomodate different barrel dia's, not in the height of the gas tube hole in the GB above the bore center, Does that make sense?  What I'm getting at (again) is ,there must be some GB that fits under the hand guard, and I don't think that the top surface of a .750" GB is any lower above the barrel centerline than the .875" (although the outside dia of the .875" will logically be larger than the .750") even if it was taller, it should only be taller by .063 (.125" difference divided by two). I wonder if you could just relieve the area where the gb interferes with the rail mount? You might consider calling back and asking them what gas block do they recommend WILL fit.

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I might follow up with them, but I really wanrted to know whether anyone had any experience with the MGI adjustable tube?  That would allow me to use any lo pro block.

I have no PERSONAL experience but have read of them breaking the adjustment off. Then again I read this on the internet and we all know how that goes.

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