I use the slip on also, with the big stuff (444,45/70,500) which is what I usually hunt with. They are fat, also have RIMS that help prevent slipping. Also as was shown in Petes picture, you need a hole in the sleeve for the sling stud to go through, that ensures that the sleeve does not slip forward. That is when it is more likely to be loose, turn on the stock, and drop ammo. I usually carry 7 in the 9 round sleeve, I really cant conceive of needing more.