Thread: AR 10 tools
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Old September 12, 2019, 22:50   #18
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A loose barrel nut and loose scope mount are two of the most common issues for AR 15/10 vertical stringing along with ammunition (more evident in handloads), loose suppressor or muzzle device. Of course it can be shooter induced from poor breath control, inconsistent pressure on barrel or pistol grip but assume it's mechanical if strings from a good rest off a bench. Have seen loose barrel nuts on two Palmetto factory built uppers as at times never know who they contract screwing them together for them. I would check scope/mounts first then pull gas tube and just see how easily the barrel nut turns. Once remove the gas tube have removed barrel nuts using bare hand without a wrench three times from one factory and two home built uppers.

Do you "bed" your barrel extension when install your barrels? It helps keep barrel from shifting as the heat from firing and the different rates of expansion of a stainless barrel extension in aluminum upper can have the two expanding at different rates. Blue Locktite is most commonly used among folks I know and it helps prevent dissimilar-metal galvanic corrosion protection if have occasions where rifle gets good and wet.

While the receivers finish prevent most dissimilar metal issues have had three uppers sent by folks that live and shoot in salt water environments have all sorts of issues if needs a tear down. One was so bad the steel barrel nut had interacted so badly with the aluminum it pulled the threads off as nut was removed and had kept it wet with PB Blaster for three days before put the wrench to it. It's owner did take a lot of "survival and in-field shooting" classes in Florida and said rifle was fully submerged in salt water many times and then not well cleaned till a few days after his weekend classes thus rifle was full of corrosion and he was having to replace the trigger group as well on his lower.

Here is a link to the guidebook on most common Locktite products for pdf download:

As mentioned have had to shim some when using someone's $39 upper bought on clearance and can't help but believe many of the lower price clearance items sometimes may be slightly out of spec units and same with extensions on $49 to $79 retail barrels. Get a loose upper and a smallish extension for same build and have had to wrap entire extension in shim stock. When do this I coat it all in blue Locktite as shimstock can often be of unknown alloy. Some say proper torque value on the barrel nut snug all up well enough bedding is redundant but I do it as seems to help and generally use Tefgel, Permatex, Lanacote, Locktite LB 8150 or sometimes whatever is close that know will work as an anti seize on dissimilar metals but Locktite says their standard blue Locktite is a good to use as an anti seize as well as medium strength thread locker.

I will use a coating of anti seize on inside of gas block, end of gas tube that inserts in gas block, threads of buffer tube and other areas. Since live on 55,000 acre lake and realize a life amd death escape and evasion scenario may involve a PFD and swimming/dog paddling or deep water wading for a few miles have some wet water end of the world, Mad Max, zombie apocalypse rifles built up. After some experience with rifles used not only in salt water but heavy mineral laden or just muddy water on rifles used by guys who go play "Army" or practice survival skills in field often have issues with corrosion in their rifles as well. I am past paying someone to torture me for a three day weekend course in some remote area of South Florida.

Bonus off topic material:
Also have clothing that dries quickly when get out and prevents many of the common issues like trench foot from wet socks or jock itch from spending days in cotton underwear/pants that are getting wet, drying plus repeated wet/dry cycles over time and can't carry extra panties or stockings. The new shrapnel resistant PUGs underwear dot mil is using has great antimicrobial treatments as well.
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