Q: My daughter has begun clay shooting with me and is really enjoying it. Being of slight build, she is using 21-gram 12-gauge cartridges at present and, I have to say, doing rather well. One friend said that these light load cartridges “punch above their weight” and that seems to be true. Is it? And if so, why is that?
A: Yes, it is true that lighter load cartridges can and often do perform above the standard that you might naturally expect.
The single largest factor in this, borne out over many years of cartridge testing, is the lower sectional density of the shot charge in lighter load cartridges compared with heavier ones.
What this means in practice is that the shot column inside the cartridge is shorter (25 per cent shorter compared with a 28 gram load). This results in proportionately lower set-back forces as the shot column is accelerated upon ignition, which in turn significantly reduces the crushing of the lower layers of the lead shot load by the layers above. The reduced crushing forces mean that there are fewer deformed pellets in the shot charge. The less deformed, more truly round pellets tend to travel with less dispersion from their line of flight than damaged pellets do. This outcome of all this is that a higher percentage of the pellets in the shot charge arrive at the target in a useful pattern.
Obviously there will be 25 per cent fewer pellets in the shot charge to begin with (provided that the same size shot is used) but, with a greater percentage of them staying in the effective pattern longer, this deficit in pellet numbers is partially redressed.
The result is that with cartridges containing shot of comparable hardness and size, a 21-gram cartridge is able to achieve greater effective clay-breaking patterns than might be imagined. My own experience and that of many others (your daughter included) supports this. Richard Atkins