I'm working on loading for a .338 LM, and my two choices for presses were my Forster Co-Ax or my Dillon 550. Chose the Coax after calling Forster and checking that the 'LS' jaws should fit a .338LM.
Well, got back from the road and there was a nice new set of LS jaws waiting for me, so I took the standard jaws off the press, put the new ones on, and promptly discovered the case head/ rim of the .338 stuff wouldn't *quite* fit. It'd kinda 'snap' in place but getting it out was a royal PITA - had to take a small flat blade screw driver and spread the jaws just an RCH further to get the case out of there. I had already screwed the spreader post up as far as it will go - there is no more to be had that I can tell.
It's looking like the Forster LS jaws were designed with the .532 'magnum' size case heads everything else *except* the .338 LM uses (.588). So... while I'm sure down the road I'll be glad I have the extra set of jaws for the press, right now it looks like I'm a little bit screwed - unless of course I missed something and there is some other way to make the jaws work properly with this cartridge (short of grinding on them)?
Somewhere around here I've got an adapter for the Co-Ax to take regular RCBS/Redding type shell holders. I'm a little worried that might take up some vertical space that may prove necessary. The other option would be to order the shellplate for the Dillon 550 to take the .338 LM case head.
There are two different versions of brass available for the caliber, as evidenced by the two different shell holders available (see RCBS's offerings). One shell holder is for Weatherby, the other for Rigby-sized brass. You may be limited in the brass you can use.
According to my old Lyman book, the case head diameter for Rigby brass is 0.586", and Weatherby (378) is 0.603". If your 0.588" is what you mic'ed, then it seems that the Hornady stuff conforms to the smaller spec. So, maybe 338LM isn't workable on the Forster, at least not w/o some adjustment.
The universal shell holder adapter and shell holder should not affect the room you have to work with, unless the bottom of your seating die was already flush with the underside of the top of the frame (meaning it would need to be adjusted up into the die slot). Even then, the open slot of the die holder gives you some access room too.
The length of stroke on the co-ax is not the greatest in the world, but changing shell holders does not affect length of stroke, because you would adjust the die upwards an equal amount.