Home Forums Hunting & Shooting Ask The Gunwriters Case Capacity vs Velocity

Blind reliance on the all-too-well established bar-stool or barber-shop (BS) ballistics makes it hard for some shooters to understand or accept the effects of certain proven interior-ballistics principles that make these cartridges work as I've designed them to work. The toughest knot for some to swallow is the fact that by (a) making the case of a new cartridge a good bit more capacious than that of an older cartridge, then (b) loading it with a larger charge but (c) not to its maximum safe pressures, (d) the same bullet can be propelled faster but without peak chamber pressures as high as those in the smaller cartridge at its lower velocity. This phenomenon has been a solid part of interior ballistics as long as there've been cartridges and rifles. The loading manuals are full of examples.



Let's look at the loads for two cartridges, chosen pretty much at random from the 50th Anniversary edition of the Sierra rifle manual � the obviously smaller .300 Savage and the obviously larger .30-06, both loaded with the Sierra 165-grain hollow-point boat-tail bullets, using the same seven powders. As the table shows, you can load the .30-06 somewhat lighter than it can stand, with slightly more powder than the top high-pressure loads in the .300 Savage, and gain a respectable amount of velocity at milder pressures.



Compare the powder charges and the muzzle velocities in italics with those to the right and the left of them. A few more grains of powder in the larger .30-06 case � but not enough more powder to raise the .30-06's peak pressures to their maximum � propel the bullets faster than the smaller charges in the Savage at maximum peak pressures for the smaller cartridge. The italicized velocities are not only higher than the .300 Savage could safely produce � their pressures are lower than the maximum for the .30-06, which means they're easier on the barrel than top-velocity loads in either of the two cartridges would be.



Similarly, all the Howell cartridges can be loaded to hotter velocities and higher peak pressures than I designed them for. But that's for the individual handloaders of these cartridges to decide for themselves � whether a little more velocity is worth more to them than longer barrel life. Longer accuracy life for the barrel is integral to the design philosophy behind these cartridges. It isn't the only purpose behind these designs, of course, but it's important to many of us.



.300 Savage, 165-gr Sierra HPBT � � � � � � .30-06, 165-gr Sierra HPBT

powder ... charge ... velocity (maximum) � � charge ... velocity � charge ... velocity (maximum)

IMR-3031 ... 38.0 gr ... 2,500 ft/sec � � 44.2 gr ... 2,600 ft/sec � 46.1 gr ... 2,700 ft/sec

W-748 ...... 40.6 gr ... 2,400 ft/sec �� 47.0 gr ... 2,600 ft/sec � 49.3 gr ... 2,700 ft/sec

BL-C(2) ..... 40.5 gr ... 2,400 ft/sec � � 45.7 gr ... 2,600 ft/sec � 47.5 gr ... 2,700 ft/sec

IMR-4895 ... 40.4 gr ... 2,500 ft/sec � � 45.7 gr ... 2,600 ft/sec � 47.8 gr ... 2,700 ft/sec

IMR-4064 ... 41.1 gr ... 2,500 ft/sec � � 47.9 gr ... 2,700 ft/sec � 49.6 gr ... 2,800 ft/sec

IMR-4320 ... 41.1 gr ... 2,500 ft/sec � � 48.9 gr ... 2,700 ft/sec � 50.9 gr ... 2,800 ft/sec

H-380 ........ 45.5 gr ... 2,400 ft/sec � � 49.2 gr ... 2,700 ft/sec � 51.1 gr ... 2,800 ft/sec



Some eagle-eyed soul is sure to notice in the Sierra manual that the test rifles had a 22-inch barrel on the .300 Savage and a 26-inch barrel on the .30-06. All right, duly noted � but that difference in barrel lengths is not enough to account for all the velocity gains in the submaximum .30-06 loads (as much as 300 ft/sec gain in velocity with H-380).