[Jeff Higgins]

Momentum = mass x velocity; energy = mass x velocity^2. Energy figures are very deceptive when discussing terminal ballistics, as they significantly weight velocity. Lighter, faster projectiles from a given size power plant (be it compressed air, a compressed spring, or gunpowder in a case) will always show higher energy numbers than heavier, slower projectiles. Heavy and slow usually wins the momentum calculation, however.

I've run my own rather extensive ballistics tests on my various air guns. The spring-air guns deliver the most energy with the middle weight pellets, dropping off with either heavier or lighter pellets. The pneumatics, however, deliver more energy with the heaviest pellets I can find in a given caliber. I think both of these traits have more to do with power plant efficiency.

As far as penetration, I have fired a variety of pellet weights in .20 and .22 caliber into various test media. Everything from the "soft pine" mentioned in vintage Sheridan ads to wet phone books. Pretty predicable results, but it's nice to see it play out as predicted: heavier pellets, even in the spring-air guns after having exceeded their most efficient pellet weight, simply penetrate better. The heavier the better.

The only fly in this ointment is trajectory. The heaviest pellet I currently use is the .22 caliber JSB Exact Jumbo Monster, at 25.39 grains. Neither of my most powerful rifles (steroid Benjamin 392 pneumatic or RWS 48 spring-piston) will crack 600 fps with this pellet. That can be a real factor in my back yard, where my longest shot can be 40 yards. If I zero it at that range, its mid range trajectory will have it shooting right over a rat. If I zero it at, say, 20 yards, it will shoot under a rat at long range. "Standard" weight for .22 caliber is ~14.5 grains. Both rifles are well into the mid 800 fps range with that weight. I can zero at 30 and pretty much hold dead on a rat anywhere I can see them around the back yard.

Playing with this stuff is fun but, in the end, dead is dead. I've pretty much gone back to 14.6 grain H&N field trophy pellets for all of my .22 shooting. I've gone for trajectory and accuracy over weight. These things shoot through every rat I hit (as do the 14.3 grain Sheridan .20 caliber pellets), and hitting is easier with them. That's what really counts, all theory aside.