At one time it wasn't all that uncommon to soft solder scope bases on,,BUT that was in addition to the screws that normally hold them on.
The soft solder was meant for extra hold,,not to make up for poor fit between the base and the action surface.
Soft solder is a very poor gap filler if you expect any strength or rigidity from it.
It can take quite a bit of recoil all by itself if a good job of sweat soldering is done.
That means a very close fit betw the base and the action surface (or the 1/2 ring and the scope tube as in some Euro claw mt set ups).
You just can't get away from that fact if you are soldering things together.
Using glass bedding compound under scope mt bases is usually to correct poor fit betw that base and the action.
It can also do a good job sticking things together.
It does not showcase top notch workmanship if used for the former reason alone.
Just my view of things..
