Still no one has really answered my question. What is my barrel twist and is that appropriate for this bullet? That may answer everything.
Take a tightly patched cleaning rod and shove it down the bore. Rod must have a free turning handle. Mark the rod using tape or such and count the turns it makes over a measured travel. Do some math and get your "twist" or turns per inch.
If the barrel is not some how fubar, the main factors I am aware of here are velocity and length of the bullet. Faster, slower, longer, shorter. That's about all you can play with and is most easily done of you reload. You can stablize just about anything if you get those right, out to 30 yards. When the bullet eventually slows down in flight the stability would change.
I've fired bullets meant for a 380 ACP out of a 38 special that shot just fine, and they were .003" smaller than the correct .357" of a 38 special. They shot just fine. I found that surprising, but they did.
At that's my understanding and it has worked to solve many poor grouping issues for me. But again, if the barrel is fubar somehow, not sure anything will fix it.
