quote:
Originally posted by PC:
Does it depend at all on the recoil of the rifle, ie .458 lott etc. should be tighter than a .222 rem ??
PC,
Not really, in practical situations. I guess if a rifle was clamped down where the weapon could not move with the recoil the heavier calibers might need larger fasteners torqued to a higher degree that smaller calibers would.
Torquing a fastener is a process done to place a pre-load on the fastener that results in enough friction (tension) to overcome whatever force is going to be trying to separate whatever joint is being held together by the fastener.
Recoil does not try to “pull†screws out...it tries to “shear†them off.
The common sizes of base and ring screws are plenty strong enough to withstand the recoil (shearing) forces generated by just about any shoulder fired weapon...even with really large and heavy scopes attached. Assuming that some amount of pre-load is present after tightening them down.
Ask just about any manufacturer of scopes/bases/rings and they will tell you that the “amount†of torque is far less important than the consistency of the torque among the screws. The idea is to get all the screws that are acting in conjunction with each other to equal amounts of torque.
The other thing that allot of guys forget about is the stress applied to a torqued fastener. Screws and bolts actually stretch when torqued and over a period of time, depending on the number of times they have been taken out and then re-torqued, the material can fatigue to the point that it will fail.
When you hear someone talking about “shearing off†a base screw you will normally find that it was an old screw that had been removed and re-installed many times and that fastener had just reached its fatigue limit.