...you can manipulate patterns. To tighten your IM pattern cores, try the old standby for trap shooters - Green Dot. This is on the slower side of the burn rate for target load (1 - 1 1/8 ounce) data - yet is fast enough to reduce muzzle pressure. Get that: the burn rate is slower to lessen the effect of acceleration set-back, but fast enough to keep muzzle exit pressure low.
This combination will tighten the pattern core. Be certain to use high antimony "magnum" grade target shot.