Trying to find out a ballpark velocity for this load. 300 gr. LFNGC with 22.5 grs. W296 in a
Ruger Redhawk 45 Colt, 5 1/2" barrel.
Starline brass and WLP primers.
Anyone shoot similar set-up?

I've run 19gr under a 300grLFPGC for 960fps in my 4 5/8" RBH. You are pushing into the 1200fps range w/ that load.

23 gr. will give 1200 fps.

I would start at 21 gr and work up. 22.5 might be just out of the accuracy zone.
I use the 335 LBT and a Lyman that casts at 342 gr with 21.5 gr of 296 for 1160 and 1167 fps respectively.
You might find 22 gr is more accurate, so just test your loads. No animal on earth will know any velocity difference. Adding more and more powder will only give you a very small gain anyway.

I've shot a 300g Lasercast out of a Vaquero Bisley using 22.0 g. of H110 for 1210FPS out of a 5.5 barrel; but it has brutal recoil that is handled better with the Bisley frame but still it's not a load I do a lot of plinking with. I have other lower velocity rounds for the plinking stuff.