Re: G10 vs. Aluminum Pillars?
I've made them from AL and from Steel, AL is easy to machine and bonds very well to numerous bedding compounds. Based on the calculations below, I see no reason to change to anything.
The general Cte numbers on AL and Steel are 13uin/in*F and 7 uin/in*F
This means
1" long pillar that goes from 50*F - 90*F = 40*F change
Length*Cte*dT = dL
The difference between them is going to be
Lenth*dCte*dT = dL
1"*(13-6.5uin/in)*40=dL = 0.00026"
The change in torque between the steel and the AL is dependent upon that deflection level and the material stiffness. AL is 1/3 the stiffness of steel
Neglecting to show the calculations for the load involved (simplicity) on a pillar, I'm getting about 2.7 in-lbs difference in screw torque for a 40* change in temp as if there was no pillar in the front and a pillar in the rear and assuming the glass stock doesn't change shape at all either (which is a big assumption).
Epoxy resins have about 5x's the average Cte of the metals in question, they're going to be a major player as well.
If there's similar sized pillars in the front and rear action screws it drops even more.
If you have a 1" long pillar in the rear and a 3/4" pillar in the front and they have the same cross section, the difference in torque is
2.7 in-lb * (1-.75) = ~.68 in-lbs
Does it really matter?
In fact, I don't think the pillars are the question at that point, the question is "Should we be making stocks out of fiberglass and embedding metals in them if we care about differences like this, or should we go the route of the BR heavy gun guys and machine the stock from a billet piece of AL or steel to match the action and barrel?"
