Hello:
This may have been posted a while ago on SSS:
Please accept that chambers and unfired and fired cases vary. They produce some challenging bullet to bore to case mouth fit issues.
Forster Products has had a case trimmer setup that works for me with Rocky Mountain cases and STARLINE 50-70/90 Sharps cases, once they are cut to rough length with a chop saw.
Unless something has recently changed, the Forster trim-to-length tool must be the "Classic" Model with 5 3/8" base. This takes the #5 collet and larger collets to fit the .640" - .650" rim diameters, and it has a slightly larger cutter diameter to handle the SIZED mouth OD of.496". Either .496" or larger will be needed. The original Forster tool has a cutter OD of .490". The .006" difference matters. Even with this setup, I encounter a few cases that the cutter OD leaves with a micro outer edge untrimmed. I hand file or it disappears when outside chamfered.
Order a Classic 5 3/8" with #6 collet and pilots CP 1500, which is .500" and CP 1495, which is .495" so the cases fit straight/squarely in the collet.
This has worked, but barely. I have had larger cutters and reamers custom profiled so their tails have the same dimensions as the standard Forster ones, but that's costly these days.
Another way to trim might be to get a cheap Chinese mini-lathe with a collet.
I have made 56-50 cases from STARLINE 50 SHARPS. LOTS of work, but if salt bath annealed after each shot, they have a good lifespan.
Please report what you do and the results. Thanks.
If you PM me your email address, I will send you my files about this quest.
El Supremo/ Kevin Tinny