I'll assume you are talking about the low velocity M118 or M196 casings... I've tried several ways of "reloading" them, and found the best use for them is making replicas... The ventholes in them are around the side of the high pressure chamber, which makes it impossible to get anything to cover them enough to make them work again. You could drill out the base and force a 38BLP blank (if you can find any) (the same blank as used in the M212 nylon casing as used in the 781 chalk rounds) and they would function, but that's a lot of work per casing. If you have a quantity, I'd be interested in them if you decide not to mess with them.
Good casings for reloading are either the Xact impact casings (aluminum) from Brassman Brass that use a 38 short colt blank but are easy to reload, or other sources (already fired) or if you want brand new real high/low pressure style, Reloadableshells.com sells very nice smokeless casings in a very wide range of styles. GROG