you can get a .45 inline and use .357 bullets in an MMP blue sabot.
play with a powder, bullet combo that works in that gun.
My daughter is using a Rossi .45 youth stainless with blue MMP sabots around Hornady .357 XTP's with 50 to 70 grains Triple7 or Pyrodex.
50 grains is equal to magnum 70 grains is pushing .357 maximum velocities.
Plenty for taking big deer at 20 yrds, and not overkill on rabbit and such.
I am really suprised at how well this thing shoots.
It's not up to the long distance shooting of a TC or CVA Optima, but very accurate to 25 yrds. I can make one hole with it consistantly at those ranges.
This Rossi is hers and comes with a recoil pad, but I bought another recoil pad to extend the butt for me. Makes a perfect featherweight/carbine style rifle for lugging around allday