Re: Any Modifications to make normal stock fit J-Lock?
I don't know who "it" is (you might put up a link to where you saw that info), but your Long-action 300 Ultra Mag will NOT fit in a standard short action HS Precision M24 stock. Of course, that has nothing to do with the J-lock.
If you make certain you are looking at the Long Action M24 stock, you should be fine.