What is the 22BR'A' ? Am building a new 22CF rifle and the 22BR is very high on my list. However, I keep reading 22BR'A'. Is the 'A' simply added for the 22BR that has the shoulder blown out like an Ackley cartridge for additional powder or is it something else? Is there a dimensioned case drawing available? I've been able to find none. Thanks for your help.