Roll Crimp versus Fold Crimp
Quote:
Originally Posted by
SuperBlazingSabots
** Roll crimping produces lower pressures due to less resistance from the roll crimp.
11. A fold crimp will further enhance ignition as the pressures are known to be much higher with fold crimp, you also need a bit less powder this way!
These are oft repeated generalizations that, like so many in the shotshell world, are not necessarily so. Particularly in a shotshell world dominated by one piece plastic wads.
In most side by side comparisons that assert lower pressure for roll crimped shotshells, the same load is assembled in hulls of the same unfired length. Naturally, the longer overall loaded length of the roll crimped example is usually not mentioned. In reality the pressure difference is more a matter of available loaded case volume than crimp type.
Probably one of the best one sentence summations can be found on page 38 of the BPI 4th Edition Buckshot Manual:
"A well made roll-crimp will produce about the same amount of back-pressure on a load to generate near the same PSI reading of a fold crimp."
I trust this helps.
RMc