So I take it from both your replies that COL might make a difference in accuracy after all. That makes sense to me but it brings up another bit of confusion on my part.

I have been seating the bullet so that I could crimp into the cannelure. That distance could be varied a little by the trim length of the case -- but not much.

If one is to crimp into the cannelure it doesn't seem that cartridge overall length can be varied significantly.

I also have been under the impression that unless the bullet is crimped, the recoil from the firing of one barrel could possibly dislodge the bullet from the case in the other (unfired) barrel.

Can one rely on uncrimped bullets in a 470 in a dangerous game situation?