Neil Jones of Custom Produsts
www.neiljones.com makes a pretty nice bushing type shoulder bumping die also a seater they run about $200 a set but with his bushing set up you could use those dies for a 260,308,243AI,etc. Jim Cartensen (563) 689-6258 is another custom die maker. I'd sure give those guys a call. I haven't use the Lee collet dies so cann't comment. I've got Neils dies for my 17machIV thru 30-378 and the odd ball stuff like 30x44,30x47,30IHMSA,7x47AI and 6brshortentalldog some of those have 30,37 and 40 degree shoulders. I've got one set of his forming dies also. I think you right buy the good ones first was about 20yrs ago got hooked up with Neils dies. Well good luck