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threads on pri comp very tight


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Hi Guys    I probably have answered my own question but here goes. when we went to screw on the PRI muzzle brake it didnt want to freely turn . we had moly grease and a lil oil on the muzzle threads and a lil inside the comp....I think its the fact that they have anodized both the pri and the barrel that this causes the interference?  I know we didnt have it cross threaded,but geez at one point it even squeeked.....we backed it out, then went forward a number of times...I just dont remember ever having this happened on my other two builds? Did we screw the pooch? <dontknow>  Wash

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They are std SAE 5/8 threads (if 308 ), if you think they are tight , just dress them up with a die & tap.

My PRI went on no problem ,but on bare S/S bbl. threads .The PRI brakes are very well done ,It may well be your bbl. threads that need cleaning up .

Are you using a crush washer or going the shim route for the brake ? If shimming , You can use blue loc-tite on the threads to keep the brake tight. I used a 0.002 shim to line my custom made one up , but it looks like its part of the barrel.


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Whew !  Thanks guys...you know ive got the same exact combo on two other weapons and dont remember the pri having this problemo....we backed it on/off with moly and lube ,but geez I know its not cross threaded...you could see the threads had turned a different color telling me the coating was being taken off the barrel.. and oh so tight! We used the timing shims...yes they are a pain!

:)  Wash

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AAC offers precision shims kits for aligning and timing muzzle devices without the use of crushwashers.

Nice idea, went to order some, but they are rigidly attached to UPS ground shipping, so a 8$ pack of washers that could go in a 1st class envelope requires $20 Ground shipping to HI? 

I hate these outfits that will not give you alternatives for shipping method and end up charging more for shipping than the damn parts cost.........

/Rant off

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Be extremely careful if it is stainless steel (barrel & comp).  Stainless isn’t forgiving like steel, when you start to bind it (i.e. makes noise’s or you feel it crunching) –it is starting to gall and if you go much further it will completely lock up and you are out of luck.  Galling is the local roughing of the surface/forming of protrusion between the sliding surfaces and stainless steel is very bad for it.    Survivalshop is correct – use a tap/die to clean up the threads if necessary (you can also use a wire brush on a dremel at low to moderate speed to clean them up if loose material is present).  Then use just a touch of high temperature anti-seize to keep it from galling and make it easier to spin on/off.  High temperatures combined with tight threads on stainless steel is a bad thing without a little anti-seize (we have had to cut off numerous stainless bolts of all sizes at work when folks forget to put a little moly based anti-seize on them). 

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