I recall that Kit Ravenshear like to have the plug removable by hand. It seems nutty to me.
But to over tighten, you are actually weakening the assembly, pre-stressing the threads as it were. There is a balance to be struck between too loose and too tight.
Its pretty difficult to over stress even a 5/8" plug with 12" wrench unless one is trying too hard. Putting this much pressure on things tends to mark the breech plug with wrench tracks. I use more pressure when fitting since a little crush keeps things from getting loose if the plug is removed and re-installed. But once fit the plug only needs 1/32 turn past contact to be snug enough for any purpose. In a 16 tpi this is not much. .002 or so.
In many breech plugs the weak point is not the threads. It at the face of the breech plug where the barrel wall is thinned by being drilled and threaded this is the area the contains all the breech thrust. This is not very important with most plugs and breech sizes. But a 1" barrel with a 3/4 plug is about as thin as I would want.
This would be the area that would concern me in over-torquing the plug.
Then we have to consider how much a large diameter vent liner weakens this area.
Given the strength of the typical threaded breech plug its unlikely that the threads are going to get looser from pressure, my comments before were probably "ill advised" after thinking if over. The plug is not like a bolt/locking lug setup in a modern gun in that they will become fouled and this will keep them from further movement so then cannot slop around much.
However, my comments on accuracy are valid I think.
If the breech fit will allow the barrel to move in relation to the tang fixed in the the stock there WILL be change in point of impact. This occurs in MLs with hooked breeches and it occurs in breechloaders when there are minute movements (and there always are) of the barrel shank in the receiver. This is so hard to control that even high strength adhesives will no eliminate it for more than a few shots.
I thought this was BS given how tight many modern guns are assembled until another shooter sent me a study of the problem then I had to eat crow.
The first 3-4 threads carry virtually all the load in a typical V or Acme thread. The "loose" threads closer to the breech in BL action then are loose and can move microscopically. Between the breech face and the front of the receiver even a small movement, .0001 can cause an increase in groups size.
ML rifles with "lockable" hooked breeches are more accurate and consistent than "free" hooked breeches. So a plug that could allow the breech to move could cause problems too. This gets more apparent if the rear sight is on the standing breech.
Dan
