A few days ago remshooter asked if he could use a 30-06 Factory Crimp Die for 30-30. Fishhawk and I told him he could use it by holding the cartridge upside down in the top of the FCD. Today I did a very similar thing. I'm loading for an 1889 Swiss rifle with 7.5X55 mm brass cut back to 53.5mm, and avoiding overworking the necks by avoiding sizing and using paper patched bullets that fit into the expanded necks. I initially used .314" boolits in the Prvi Partizan cases to fireform them. I found that they required a bit of extra effort to chamber them, and after firing the case mouths were pinched down to .312". I had to cut them all the way back to 53.5mm to eliminate the pinch in my chamber. Sure, the Swiss GP90/23 was 54.5mm long, but it used a .308" FMJ bullet which would come out of that .312" opening without interference. After trimming and chamfering, the I.D. of my necks was .321", a nice snug fit for the .316" NuJudge boolits I'd patched up to .323". Anyway, after all this long background, the point is that the fat necks mean that these cases have problems with Lee 7.55X55mm dies. Can't use them with either the full length or collet neck sizing dies, they have to be decapped with the generic Lee decapping die. They just barely will go into the seating die, for which I'm grateful as I didn't have an alternative. I had to put a little flare on the cases with the generic Lee flaring die to seat the bullets without tearing the patches, but that left the problem of taking the flare out. (Actually, a good firm forward shove of the operating handle would chamber the cartridges and removed the flare perfectly, but I prefer them to go in easily.) No way would those necks go into the 7.5X55mm FCD. I thought they might work in an 8mm Mauser FCD, but the 8mm case body is much smaller than the 7.5, so it was no go. But I could turn the cartridges upside down, insert the case mouths into the jaws of the 8mm FCD collet, and adjust the die so that it just took the flare out when the press ram was raised. The results were perfect.
The other nonstandard use I make of the FCDs is to crimp on gas checks. Sometimes you need a fatter checked boolit than you have a sizing die for. You may want to use the unsized, as cast diameter of the boolit, but that check's got to get crimped. Well, push the gas check on the shank of the boolit, hold the boolit with the check just into the top of the FCD collet, and adjust the die so it just crimps the check to the boolit diameter when the ram is raised. Perfect solution.
Sometimes you don't have a purpose made tool around, and you've got to improvise with what you've got.