Found Case trimmer that works for 56-50 and 50-70 brass.

[Sedalia Dave]

Search for a trimmer is over. 


For those wanting to trim 56-50 or 5-70 brass, A Lyman Accu-Trimmer works nicely. It uses your existing 56-50 / 50-70 shell holder. The cutter that comes standard with the trimmer is large enough to trim new or sized brass.

I have been using to to trim 50-90 Sharps brass down to 1.3" for use in my Springfield Armory 56-50 Burnside Carbine to Rifle conversion.

I'll start a separate thread covering cartridge development.

[Two Flints]

Check out this link:  https://www.cascity.com/forumhall/index.php?topic=40010.0

Not sure if this is what you're looking for.

Two Flints

[El Supremo]

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

[Sedalia Dave]

Thanks for the replies.

I Stumbled on a Lyman Accu-Trimmer at Buffalo arms. The description on the Buffalo Arms web page states that it will work for 50-70 brass. The description on the Lyman web pages states up to .458 Win.

In doing research on the discrepancy between the two descriptions, I discovered that Lyman also makes a version of Accu-Trimmer specifically for 50 BMG. A look at the parts list in the manuals shows that both versions use the exact same cutter head. I looked closer and the only physical difference is the 50 BMG version uses a different base and comes with the 50 cal pilot. The real shocker is the price difference. The 50 BMG version is twice the price of the standard version.

So I purchased the standard version and it will be here next week.  I'll post an update on how it works.

[Sedalia Dave]

Modified my original post.

The Lyman Accu-Trimmer works great. The only issue I had is one of my 2 shell holders did not hold the case directly inline with the pilot. When I tightened the clamp the case was not inline with the pilot. The other one did hold the case in proper alignment. Tomorrow I'll pull the shell holders and see which one worked and which one didn't