Blue is the new lead-free shot alternative from Spanish manufacturer BioAmmo. Their USP is the fact that both their cartridge cases and wads are biodegradable and can be composted, although there is no data yet on how long they take to disappear. Now theyve joined the lead-free party with Blue, an alloy of Bismuth, Zinc, Tin, and Aluminium. Sounds complicated, but what it actually does is make it more than twice as soft as steel which has some advantages. This increased softness means it has better energy transfer than steel, so gives better kills and it also means that it can be used through any choke. Under CIP rules, BioAmmo Blue should be treated as steel with the exception of any choke restriction. This means that you can use it in any gun manufactured post-1954 with nitro proof marks (NP or BNP), with suitable chamber lengths and any choke.