@Apthorpe further follow-up on your query
The research at Cranfield has lead us to move away from a 2 shot size increase to a 1-2 size increase as the penetration benefit was negligible.
Lead vs steel - a question of lethality - The British Association for Shooting and Conservation
We are now recommending the 21g limit for older guns since recently meeting with the Birmingham proof house.
The table on page 7 is correct. It relates to high-performance steel as detailed in the text next to it.
This is CIP guidance which is related to high performance steel (CIP make no recommendations on chokes for standard steel loads – doubtful you can get a standard steel load in #2 at any rate. A standard steel load should be a shot diameter of 3.25mm or smaller).
The guidance states the choke requirement for certain diameter steel shot and larger, which is outlined in the table.
In relation to number of pellets, steel is less dense than lead, and therefore for a given cartridge weight, a steel cartridge will contain more shot that a lead load. So a lighter lead load will contain more pellets than one might assume.
We will continue to update and revise our advice to take account of new research, information and products.
The research at Cranfield has lead us to move away from a 2 shot size increase to a 1-2 size increase as the penetration benefit was negligible.
Lead vs steel - a question of lethality - The British Association for Shooting and Conservation
We are now recommending the 21g limit for older guns since recently meeting with the Birmingham proof house.
The table on page 7 is correct. It relates to high-performance steel as detailed in the text next to it.
This is CIP guidance which is related to high performance steel (CIP make no recommendations on chokes for standard steel loads – doubtful you can get a standard steel load in #2 at any rate. A standard steel load should be a shot diameter of 3.25mm or smaller).
The guidance states the choke requirement for certain diameter steel shot and larger, which is outlined in the table.
In relation to number of pellets, steel is less dense than lead, and therefore for a given cartridge weight, a steel cartridge will contain more shot that a lead load. So a lighter lead load will contain more pellets than one might assume.
We will continue to update and revise our advice to take account of new research, information and products.