I don't have a 338 LM but I do use the 338 Lapua case for my 7mm AM. I have an inertia type puller as well as the RCBS collet type puller. The improved 338 Lapua case won't even fit in the inertia puller but the collet type puller works great because it takes the case out of the equation. Just get different collets for whatever caliber you have a need for and you're in business.