I have been remiss in not discussing Hornady’s new Superformance Ammunition before now. The Superformance loads attain a 100-200 fps increase in muzzle velocity at standard SAAMI pressures (ie. they are not hot loads). Hornady’s chief ballistics scientist told American Hunter …

“Until now, center-fire ammunition performance has been based on the IMR-series propellants developed in the 1930s and ’40s,” he said.

They achieve this by developing a set of new powders and blending these powders specifically for each cartridge so that all the powders burns completely inside the barrel. This allows maximum power transferred to the cartridge but also lower muzzle blast, thereby reducing recoil.

Graphs from the Superformance White Paper …

So why have handloaders not attempted this before? I am sure some have, but blending powders is dangerous because the pressure curve cannot be predicted. You cannot create a load made up of 50% of Powder A and 50% of Powder B and assume max pressure will equal (Amax+Bmax)/2 or when the maximum pressure will occur.

Currently Hornady is offering Superformance loads in .243 Win, .257 Roberts, .25-06 Rem., 6.5mm Creedmoor, , 7mm Rem Mag, .270 Win., 7mm-08 Rem., .300 Win. Mag, .300 RCM, .308 Win.
.308 Win., 30-06 Springfield, .338 Win Mag, .338 RCM, .375 H&H , .375 Ruger and .458 Win.

It is interesting to note that Hornady is not offering any intermediate/varmint cartridges. A Superformance 5.56mm round tuned for the M4 (but fully compatible with other 5.56mm systems) would be very useful.