It is going on a Fiberite (plastic) stock, correct? From what i've read, they are only made for non-aluminum stocks. Anyway, lots of lube, a good padded vise (I locked the barrel/FH in it) & lots of arm will get it to snap on. Then drink a beer, as you will need it!
They work nice with a scope, but require a little:
too get them too drop on the stock! Hope this helps.