bwana600nitro:
Welcome to NE. Depending on how long you've been lurking, you may have seen an earlier thread where I promoted the 650/90 .577 with Weldcore bullets as a cartridge whose day has finally arrived! I got flamed of course, but I'm heartened to find another kindred soul!

When discussing cartridge power and rifle weight, its a good idea to work backwards. In my opinion 11 lbs is a good 'maximum' weight for a rifle which will be carried a lot in the field. Anything heavier than that is going to tell by days end, whereas I can carry my 11 lb Manton .470 or Alex Henry 20/.577 all day in tropical heat.

Regarding recoil, about 75 ftlbs is getting up there for comfortable shooting, and 80 ftlbs is probably getting very close to a practical maximum. This means that 1850 fps with the 650gr bullet is going to fit within our paradigm, whereas 1950 fps is above. We can opt to live with the higher recoil, or either increase gun weight or drop the velocity. Personally I would opt for the latter.

My Greener conversion weighs 10 1/2 lbs, and nudges the 650-grainer along at a very modest 1665 fps. It is very pleasant to shoot all day, around 63 ftlbs recoil energy. In that action I won't go any higher, but in a new Searcy or similar I would definitely consider specifying 1850 - 1900 fps. 1850 fps will still stun buffalo with the Woodleigh 650 grainer. With a well-fitted stock, 11 lbs should be enough but it will certainly still boot! Depends what you want in the long run.

Remember there are two Woodleigh 650-grainers, one thin-jacketed for BP which would be a bomb on hogs/elk/bear etc, and a tougher one for buffalo and other thick-skinned game.

Its a lot of fun planning a new rifle, especially a .577!