While it is generally true that the load that produces the highest velocity with a long barrel will also produce the highest velocity in a shorter barrel, that does not equate to that same load being "best". I don't mean accuracy either. There is more to consider. Short barrels have higher muzzle pressures, which are responsible for an awful lot of the noise and even a substantial part of the recoil.For instance, if I ask QuickLoad for the fastest load under a 150gr SST using a 24" barrel, without getting over 107% compressed, it gives me IMR4895, BLC-2, Win748 or IMR 3031, all within 11 fps of each other at about 2,990.
The recoil with a 7lb 8oz gun is about 11.06ft.lb on bullet exit and totals 17.41 ft/lb with the "Gas After-effect" with about 8,100psi muzzle pressure.
If I shorten the barrel to 18", those same 4 powders are in the top of the list for velocity (about 2,810) but the muzzle pressure is up to about 11,000psi. Recoil at bullet exit is now at 9.76 and total after gas effect is 15.99.
If I were willing to give up just 20fps, down to 2,778, AR-Comp gets me 9.37 and 15.05, a further reduction of 6% of recoil, a muzzle pressure reduction of 1,300psi (12%) and with just a 1.1% reduction in velocity. For the curious, AR-Comp gives up about 75fps tp the others at 24" but even there drops recoil to 16.23, a 6.8% reduction for just 2.3% velocity.
That may not seem like a lot and any one of us may or may not care but it is very close to bringing the blast of that 18" barrel down to 24" levels. Personally, I like losing 6% of my recoil for virtually no down-side.
