Here's just a SWAG. Based on reports from this forum, people generally experienced 30 fps increase in velocity with a can vs. no can.
That means, pressure is also a little higher, and the theory is that the can
acts as a "psuedo-barrel extension". If you follow the theory of OCW on barrel exit time and velocity affect on timing the bullet exit to find the sweet harmonic node where the barrel is pointing in the exact same spot each shot, then you might try the following.
Assuming a slight increase in velocity with can. (You can actually test your specific rifle verify this---higher velocity with can or not?)
1) Seat bullet a little less deep. Less seating will reduce pressure and therefor slow down its velocity and barrel exit time to offset any gain its getting from the can.
2) Decrease powder charge slightly to lower velocity to offset any increase from can.
3) Check velocity before can to with can, and then velocity with changes 1 and 2 above. Try to match velocity pre-can with these changes.
4) You can try both 1 and 2 combined as well to get a pre-can velocity match.
I'm not 100% sure that any of this will work, but if you can get a better match to bullet exit timing by matching pre-can velocity it may help in theory at least..... LOTS OF STUFF IN THEORY DONT PAN OUT.
But, its worth a try. Now, if your can shows decreased velocity from pre-can velocity work backwards from the above.
It may also be simply that this is more mechanical or harmonic in some respect, and that the can is just shifting the harmonics of the barrel so much that it is a problem. Try a lighter or heavier or shorter or longer can.
Because you will see that relative to your barrel design, short and fat or long and skinny, bull heavy diameter or not so, that a big weight on the end of the barrel will affect different barrels differently. It is in affect a barrel tuner, that may put you out of tune by the weight and length distribution with respect to harmonics.
Before any of this......please do check the can and threads to make sure it is not vibrating lose each shot so, every shot has a different harmonic profile due to the weight distribution difference in the can being too loose and moving around.......please do check that very first thing. Might even lock it down with blue thread.
Good Luck. Harmonics is a deep and strange subject.
There is an excellent thread here on LRH about velocity in cans reported
after install, and the average 30 fps increase most saw.
P.S. I don't have a can, never shot one, and so this is all very much theory coming from me......but I did stay at Holiday Inn recently, not even last night.....
