(the image was rotated 90 degrees to the left during uploading so elevation is actually left to right)
so this weekend i decided to test how putting a crimp (using a factory crimp die) affects my bullets. this is on a 338 win mag savage, benchrest at 100yds. this gun has an adjustable muzzle brake which i also tested if it affected accuracy open vs. closed. everything has the same amounts of the same powder, same brass, all 0.020" off the lands, and same primers. several fouler shots were taken. all were 3 round groupings except i did have an extra heavy crimp bullet so thats a 4 round group.
upper left: heavier crimp
bottom left: moderate crimp (i do remember "pulling" the bullet that hit center)
bottom right: light crimp (1 outlying round was a fouler shot)
center: 1 barnes factory round and 3 no crimp
upper right: no crimp - open muzzle brake
all shots except upper right were with a closed muzzle brake. at least 1 minute was taken between shots with the bolt open to allow for some barrel cooling. unfortunately i don't have access to a chronograph so all references to velocity will be based on if it hit high or low on the target.
it seems as though i may have gained a slight amt of velocity with mod-heavier crimping but at a loss to accuracy. i really expected to gain accuracy with crimping. a light crimp still had accuracy but similar point of impact as no crimp and closed muzzle brake. here's where i'm really scratching my head...when i opened my muzzle brake i had a completely different point of impact compared to when the same bullets were shot with a closed muzzle brake. i'm guessing that has to do with barrel harmonics but at 100 yards should i really be seeing that much difference (basically 1 inch of windage and 2 inches of elevation)?
my take away from this weekend is that i'm not going to crimp and will shoot with a closed muzzle brake all the time.