A buddy of mine had a pistol lower assembled by a gunsmith at a LGS. He bought a law tactical folding stock adapter and asked me to install it for him. I read up on it a saw that it didn't involve anything above my skill lever so I told him I would do it. I took a look at the lower and noticed the castle nut on the buffer tube was not staked which I though was odd but also was going in to make the install easier. Then I discovered that the gunsmith used thread lock on the castle nut and on the buffer tube possibly. From what I have learned thread lock should not be used.

Am I wrong?

Thanks in advance for the answers.

Mil spec doesn't use thread lock. Staking only. Mechanically staking it is spec because the weapon won't be torn down by the operator for cleaning, and it's service life is based on 50,000 rounds plus or twenty years plus. Also, the military uses all sorts of solvents to dip weapons in, some will attack thread locker and dissolve it. Not good. Chemical thread lockers aren't used for a lot of reasons.

On the gunsmith level, thread lockers have carried over from machine shop practices where they do get used, as staking seems to permanent and beating dents into the metal finish is considered hillbilly on finely finished firearms. Gunsmiths also like thread lockers because most owners don't know how to take it apart and it forces them to bring it back for more lucrative work. And some just don't want any comebacks for it loosening - or just don't know better. "Gunsmith" does not mean that individual is qualified to work on military spec weapons. Same as "mechanic" doesn't mean they are qualified to work on both a Kenworth and Prius.  

Then you get the rocksett crowd who think that using a ceramic adhesive that resists 2,000 F is the minimum. Same as the guy who JB welds all the intake bolts. Permanent throw away situation.

Problem is guys working in one field think they can work in others - doctors as contractors. The results can get ugly and in their mind anyone who questions them is wrong.

Don't hire rice farmers to grow your grapes.

These words might possibly be the best pearls of wisdom that I have ever read on ARFCOM.

+1 on the above.

Personally I don't use it, I don't stake either 'gasp' I check it during routine cleanings to make sure she's still tight. My constant need to swap parts makes it unnecessary for me to lock it. When I do use thread lock, I use purple. Gets the job done and is broken with mild force , no heat or solvents needed .

I use red on everything that isn't next to plastic and that's basically the grip screw.  It only takes a heat gun and 400 degrees to break it down but until then things stay put.  For small screws, I put a cigar lighter on the bit and heat them up that way.  I'm not the military and I don't have sustained fire so red is the ticket.  I have used Rocksett on thread on suppressors just because they do get hot quickly and why not.  

To each his own.  I like Red for my application which is plinking, target shooting and killing the occasional critter.  Red has never let me down.

so what happened with the lower ? did you stop ? did you bugger it up ? some heat and all was well but it just took more time ?

Thread lockers have their place with specific colors but it's not to be used in every place nor all one color.

I'd rather use green loctite than staking. RRA used RED on my old go-to AR, and F THAT. I just hope I didn't mess up the lower having to heat it up so much.

But that's me.

400 degress is nothing for aluminum.  Rock River uses red because things stay put.

Yep.

so your saying gunsmiths shouldnt work on ar's?

Depends on the buffer tube type.

If it uses a castle nut I usually just torque and stake.
If it's one of those pistol tubes that only uses an end plate, I'd use loctite.