A shorter barrel is handy, but the muzzle blast is a problem. Shooting off a bench, one wears muffs. In the field, maybe not. But if off a bench, why not leavit at 26"??
A 1-7 (you sure it is not a 1-9?) will stabalize much longer bullets. If you want accuracy, and especially accuracy at longer ranges when wind is an issue, longer bullets are the way to go. Before changing the barrel, why not load some 55's for the rifle, and some 69s, 75s and 80s.
If your rifle did not test well on the first go with 55s, I doubt twist was really the issue.