I have a 4 1/4" M97 .45 Colt. I basically shoot two loads from my gun. My everyday plinking, woods bumming, and general fun load is the 270gr SAA (actually weighs a little over 280gr) that fowler mentioned above. My load is 7.8 gr of HP38, mixed brass, Win LP primers, and crimped over the front drive band. This load runs a little over 900 fps (actual chrono) in my gun.
The other load is the RCBS 300gr SWCGC (actual weight 315gr). I load it to a little over 1,100 fps (again actual chrono) using H4227, H110 or Lil'Gun. I've settled on H110. I also crimp this bullet over the front drive band. You can crimp this bullet in the crimp grove, but the meplat is right at the end of the cyl face, allowing nor margin for potential crimp jump. You have to be real careful with charge weights when using heavier loads and reduced case capacities (when crimping over the front drive band). With a little tweaking, you can get these two loads to hit very close to the same point of impact.
I don't shoot very many of the 300gr Loads. There are times when I do want the extra power when packing the .45. Most of the time when more power is required then the .454 or .475 get the nod.
I get both of the above bullets from Montana Bullet Works.
Paul