In previous reports on new steel shot offerings from UK cartridge companies, I have explained the difficult position cartridge makers have been put into. Here we have a fresh example of how a leading UK manufacturer has tackled the uplift from standard steel cartridges – for those guns that are not steel-shot proof-tested and marked – to the ‘Formula One’ division of high performance (HP) cartridges. Cartridges designed to comply with the HP specifications, as designated by the CIP, and have higher velocity and momentum limits to work with.
HP 12-bore loads have a velocity ceiling of 430 metres per second (m/sec); just 5m/sec higher than for standard steel. In reality, this is a small increase. Shotgun cartridge velocities are more difficult to maintain within the tight limits that quality rimfire or centrefire cartridges achieve. It’s not at all uncommon for velocities to vary by rather more than +/- 5m/sec, which makes it difficult to take full advantage of the modest uplift. Note too that these CIP limits are already considered by some manufacturers to be on the conservative side.
The momentum uplift is useful. It permits a heavier shot
