Dave:
SAAMI standard is SAAMI standard. American manufacturers must merely load ammo that equals or is less than a stated Maximum Average. Case length does not matter ( except for 12g 3-1/2" and .410 bore) .
The current SAAMI standard is ANSI/SAAMI Z299.2-1992.
.410 bore 2-1/2" has a Maximum Average Pressure of 12,500 PSI
.410 bore 3" has Maximum Average Pressure of 13,500 PSI.
As Ken points out, there are 2 basic ways to achieve a particular velocity in a shell with a given shot charge.
1) small amounts of fast burning powder, which produce the stated velocity cheaply, but by developing high pressures.
2) Larger amounts of slower burning powders, which work at lower pressure, but cost more, sometimes much more.
If you found them at Wal-Mart, in the "el cheapo" section , it is like they got cheap by using the fast burning powders.
Stick with the good stuff.
My ideas - do what you want.
Regards
GKT
