Machine shop 101
Always use the right tool for the job.
Do not use Red loctite and do not use Blue Loctite.
Red Loctite is not service removable and is not designed to be used on small threads / screws.
Red Loctite is used mainly on threads = bolts 1/4 inch and larger.
Blue Loctite is service removeable - but again is not designed to be used on bolts smaller then a #10
Scope mount bolts is what is called a [censored] Thread.
The reason why it is called a [censored] thread is because it is a ODD thread that has no other use - other then to hold on a rifle scope.
Common threads on a rifle scope is 6-48 and 8-48
That means that the size of the screw is the same as a #6 drill bit or .130 and the screw has 48 threads per a inch.
Rifle scope mount threads requires a special tap, actually more then one tap (3). One to cut the thread and a second to chase the thread and a third - which is called a bottom tap which clears the thread beyond what the first two cut - down to the bottom of the hole.
Let's use 6-48 as a example.
The diameter of the screw is about .130 thousandths.
.125 thousandths is 1/8 of a inch.
We have to drill the hole smaller then the screw so we leave enough material inside of the hole to allow the tap to leave threads inside of the hole, but not so much material that the tap cannot clean out the material being tapped or else the tap would get stuck in the hole and break off - not a good thing.
Lets say that you are going to use a 75% tap, which means that we will drill the hole 75% as large as the finished thread size and will allow the tap to remove 25% of the material left inside of the hole.
For the scope screws to hold with the maximum amount of force, they need about 6 threads or 1/8 of a inch of material.
The only purpose of the Loctite is to fill in the gap between the screw and the treads in the action of the rifle or in the scope mounts themselves.
That gap is .001's of a inch. Not much room for a thick Loctite - which is the reason why we do not use a strong non service removable Loctite or a Loctite that was not designed to be used on small screws.
In order to get a thread locker to work on 6 threads, you need to use a Locquitic Primer. This cleans the threads and makes the Loctite more compatible with the screws.
Because our screws are smaller then a #10, we know that we need to use a special Loctite.
That Loctite in the past was PINK, but now has been changed to a kind of a Purple color.
It's service number is 222 MS
LOCTITE® 7471 Primer T has a 7 day on-part-life, and LOCTITE® 7649 Primer N has a 30 day on-part-life and is Ideal for cure conditions below room temperature.
So, if it's room temp or above and your going install your screws in 7 days or less, use 7471 Primer T. and then the 222 MS.
If your in colder areas use 7649 Primer N. and then the 222 MS