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9/22/2017 12:11:25 AM
Posted: 6/7/2003 10:39:08 AM EDT
I know someone who is having problems with a PRI tube I sold him. It took his two gunsmiths to line up the barrel nut and tighten it. He also says that after strap wrenching the sleeve nut it still gets loose, especially when using a forend vertical grip.

Now he's saying he should have gone KAC, but I don't see any difference in the way the outer collar tightens up. Both systems use an inner and outer nut.

Any advice to pass onto him?
Link Posted: 6/7/2003 4:41:22 PM EDT
I have had some problems with my PRI SPR tube - before I put my ARMS #35 QD mount on - I had to dremel the colla ra tad and now it cannot loosen off for the ARMS #35 is in a channel through it. Now I had a KAC FF RAS for over two years and never had any toubles and It got a much tougher work out. My guess is there is a reason the US Army went with the ARMS SPR Rail ont he PRI tubed guns...
Link Posted: 6/7/2003 4:50:41 PM EDT
[Last Edit: 6/7/2003 4:51:11 PM EDT by Raptor22]
[b]Now I had a KAC FF RAS for over two years and never had any toubles and It got a much tougher work out.[/b] I guess that its advantage lies in the two index pins that hold the FF RAS in place in relation to the barrel nut. PRI should have gone this route. [b]My guess is there is a reason the US Army went with the ARMS SPR Rail ont he PRI tubed guns.[/b] Exactly the same reason for the ARMS #38 EX Mod L for the KAC M4 RAS.
Link Posted: 6/7/2003 4:54:59 PM EDT
If I recall, the PRI tube does have two indexing pins that keep it straight up in relation to the barrel nut?
Link Posted: 6/7/2003 6:04:50 PM EDT
Originally Posted By AR223: If I recall, the PRI tube does have two indexing pins that keep it straight up in relation to the barrel nut?
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I was not sure about that since Wes at MSTN had installed mine and the sleeve nut is on very tight and I do have the ARMS SPR rail installed. Maybe blue Loctite would work. It is worth a try.
Link Posted: 6/7/2003 6:16:17 PM EDT
Try teflon tape on the threads before you screw it down. It works great on muzzle brakes and other threaded items that need to stay put and exposed to heat. It is an old trick that I used to use on header bolts that works great on firearms. IDHunt
Link Posted: 6/7/2003 6:23:21 PM EDT
Exactly, he already knows about the Teflon tape used to assemble an upper my friend sold him. Keeps everything from seizing up and keeps the threaded parts snug without vibrating loose. Does the SPR rail touch the forend outer collar at all to keep it from turning?
Link Posted: 6/7/2003 9:52:20 PM EDT
Originally Posted By AR223: Exactly, he already knows about the Teflon tape used to assemble an upper my friend sold him. Keeps everything from seizing up and keeps the threaded parts snug without vibrating loose. Does the SPR rail touch the forend outer collar at all to keep it from turning?
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The ARMS SPR rail slides over and is screwed into the top rail of the PRI tube and there are notches underneath the rail that fit snugly over the collar so nothing is going to move it.
Link Posted: 6/7/2003 10:00:16 PM EDT
Originally Posted By Raptor22: The ARMS SPR rail slides over and is screwed into the top rail of the PRI tube and there are notches underneath the rail that fit snugly over the collar so nothing is going to move it.
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So, the SPR rail is more of a barrier than a physical connection to prevent the collar from loosening... [thinking]
Link Posted: 6/8/2003 5:44:20 AM EDT
Link Posted: 6/8/2003 10:34:08 AM EDT
Another problem brought to my attention and I quote "PRI tubes are not centred on the barrel either if you look straight down the bore". I'm confused: it takes two people who regularly work on guns to line up a barrel nut that easily spins on and the PRI tube isn't straight with the barrel. [slap] I have no problems putting my uppers together and I only have hobbyist tools! [ROFL2]
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