hello Doubleguy-Welcome to the Board.

I heartily second Brother Jack. Your Crass was intended to shoot the then-standard American 12g load at about 9000-9800 psi or so. It doesnt now, nor did it back then, matter how you generate the pressure, either black or smokeless will work just fine, as long as the gun is sound, and you stay in appropriate service pressure ranges.

Some people feel like the super-low pressure 5000 psi loads are the way to go, but these sometimes do not light correctly under low temperatures. I would suggest that you use loads that are in the 8000 psi or so range, and be very careful about using heavyweight shot loads unless you confirm the stock is sound, not oil soaked, and capable of withstanding the pounding. It is likely best to pass on shot payloads of more than 1-1/16 of an oz.

Enjoy your Ithaca.

Regards

GKT

Texas Declaration of Independence 1836 -The Indictment against the dictatorship, Para.16:"It has demanded us to deliver up our arms, which are essential to our defence, the rightful property of freemen, and formidable only to tyrannical governments."