I ran into somewhat the same problem when the light went on in my head that the RCBS dies (3 die set) were sizing down my 7.62x54r cases too much. Rather than mess with sending the dies back to get reworked or going to bushing dies I decided to do something I could control. Measured about twenty once fired cases then neck sized those sane 20 cases. The numbers astounded me. And at the time boxer primed 7.62x54r cases were hard to get. So after I had an average between fired and sized cases all 20. I have some 7/8"x14tpi threaded screw stock. Chucked it in my lathe and first drilled a hole smaller than my cast bullet .3135 then reamer the hole and polished the hole with various graded of silicon carbide paper. What I was looking for was to get enough neck tension without overly sizing the case neck. I ended up with .003 on my first shot. Worked great and the Lyman M die was used to just bell the case mouth. My mini neck die isn't hardened no do I have to lube the case neck. This is not a new idea. Mini or short neck dies used to be made years ago. Then for some reason they just disappeared. Maybe because of a limited market.The way it works it you size the neck in the mini die,then use the M die to bell the case mouth. Once your case is primed and charged seat your bullet and seat the bullet. Course now boxer primed cases are easy to find. I bought 15 20 round boxes of Hansen Cartridge Company 7.62x54r ammo. Since my 1935 Finn model 27 ever sees is all cast bullets I should have enough cases till they shovel the dirt on me. If I were to start with this cartridge today I most likely would be using a bushing die if only to play around with different neck tensions. Frank