What is the best for gun smithing applications, mostly in relation to scope mounting. Are there other types of Loctite?

Blue you can break free with some torque, Red you need ALOT or torque and/or heat to break free usually. I use blue for 99% of the stuff I do including scope mounts.

There are other colors/strengths out there but dont think I would use them on a firearm (like I think green is pretty much permanent, IIRC).

J-

Thanks for that. Most companies that are good enough to send Loctite with their scope mounts, I've generally seen the blue being sent. I just wasn't sure where the red could be used in gun smithing applications.

Yep, green is evil.  It can be removed with heat.  I've broken red loose by hand, but heat definately helps.

Red has less high temp than resistance than green.

Both often require heat though.

One of the problems is that neither is rated by the manufacturer for smaller screws.
That does not prevent them from working though.

Make SURE you completely degrease both threads.

1,1,1 used to be the degreaser of choice but is banned now.
MEK works very very well.
Acetone is good.
Lacquer solvent not as well but still decent.
Alcohol not nearly as well.

ETA:

Red is for thread locking.
Green is for bearing locking.

Blue, and only a small drop.

If you use a large drop of red on small screws, you will get to do some drilling...

Per Loctite;

      Purple-screws smaller than #6 (#1-4) and for serviceable removal of screws up to 1/4"
      Blue---screws from #6-#12- can be used for larger screws for serviceable removal.
      Red---all screws from 1/4" and up as a thread locker. there are 3 types of red, each has their own strength callouts and heat range.
      Green-for bearings, shafts, cylindrical retainer and other applications. Handles constant higher heats and "wicks" into tight spots.
      Loctite website has all of the other locking type chemicals and their applications.

  When I was in Indycar, we used a lot of different Loctite products. All had a specific application/use. You will probably not use more than Red or Blue on guns.

Loctite makes a primer compound that cleans and preps the surface for Loctite. I have no idea what is in it but I use it on critical things...

I use blue for 99% of the screws and threaded accessories on my rifles.

For suppressors and flash hiders i use Rocksett.

Red on scope mounts, blue on rings.
Red on overtravel screws, maybe a dab of wicking green on sear adjustment screws.
+1 on Rocksett for brakes and flashiders if thread locking is needed.

In terms of gunsmithing, I'd have both on hand. Blue is going to be more commonly used, as most folks here have alluded to.

If you've not seen the Loctite applicator sticks, as opposed to the droppers, they are pretty frigging awesome. At least for myself, I would always cut the opening in the tube too large, and way overuse loctite-getting it not just on the threads, but my workbench, the dog, etc. And then, since the tube is so small, the loctite gnomes would come and repatriate it, leaving me having to make yet another trip to the frigging hardware store for more loctite.

The applicator sticks (think glue stick), are large enough that they are harder to misplace, solid so they don't leak, and easier to apply (at least for me).

Yes, I'm totally biased, and only wish I'd known about them sooner. They're also not horridly expensive on Amazon. Couple the ease of use, and the reduced waste (at least for me), and a stick should last a damn long time.

The ONLY gotcha with these is that you cannot retract it back into the tube once you click it...so, only expose as much as you really need for your work.

Loctite Blue Applicator Stick: http://amzn.to/1D3IZoQ
Loctite Red Applicator Stick: http://amzn.to/1MNb2kq

Just never never squeeze the air out of a bottle of Loctite.
It hardens when air is not present.

Loctite also makes the sticks with silver and copper antiseeze, white pipe seal, and purple thread loc. I use the sticks multiple times, daily on guns. No mess, or spilling.

Normal temp (like red) is 325 F).
High temp lockers (green) are 500 F.

A soldering iron usually works for smaller fasteners (irons are often slightly over 700 F).