I don't get upset when someone hi-jacks my threads, especially when they're enlightening me! Feel free to hi-jack away Randy!
Mike
Thank you, Mike.
The following are "ball-park" capacities of several .25 cal. cartridge options, determined by a pal of mine, using RL-15 - he loves the stuff - and filling to level full, as 'sliced' off using a razor blade - I believe he used an average of ten cases each. Of course, these were as fired, from barrels/chamberings which either one, or, both of us own: brass and chambers vary somewhat.
1) .250 Savage - 42.4 Gr.
2) 25x47 Lapua/HBR - 43.6
3) .250 Savage Ack. Imp. -46.7 Gr. (this is for my .350" long-neck version - slightly more than a "true" .250 Sav. A.I.)
4) .257 A.I. Roberts - 58.4 Gr.
5) .257 IdiotMag (.25/300WSM) - 76.3 Gr.
6) .257 Weatherby Mag. - 76.3 Gr.
Not the most scientific comparison, none the less, a reasonable perspective.
There are, as pointed out in this thread, many good options - for pure horsepower, and
[probably] a more commonly available reamer, the .257 Wby. is though to beat: even with the contemporary powder selections, there is always a point of diminishing returns.
The smaller cases are quite efficient, and, with the lighter bullets - 100 Gr. and under - can deliver surprising velocities! Really, your best option is to obtain one of each!

