Yes, you can use a larger caliber suppressor on a smaller caliber firearm, provided the projectile diameter and pressure are equal to or less than the caliber the DEFCAN was designed for.
A rifle cartridge can be used in a larger rifle caliber suppressor, and a pistol cartridge can be used in a larger pistol caliber suppressor. Do not use a pistol caliber suppressor on a rifle cartridge due to pressure issues.