Hello:
According to Threads and Posts here, some older Lyman 56-50 dies may have been shortened 50-70 ones, but recent ones might be ok. I don't know how to tell them apart.
I HAVE three Lyman 50-70 bullet moulds with the SAME bullet number on them. The profiles on the bullets are visibly different, having been cut with different cherries. Lyman changes things.
I have no recent experience with RCBS 56-50 dies.
Loved RCBS years ago, but now some RCBS stuff is from ASIA and that person in customer service may not know about 56-50 chamber variations.
Remember that the Armisport 56-50 chamber can be different dim's than original Spencer chambers.
So can the die set maker indicate which chamber the die set is for?
CH4D makes three different chamber sets:
Original. Armisport. Custom cut TIGHT for RMC cases with a Pacific Tool, piloted carbide reamer.
A big part of the dimensional variation is the taper IN THE CHAMBER.
There have been variations in the chamber dimensions of Armisport 56-50 Spencers over many years, which when combined with the inside taper in Starline brass make for issues.
Both are manageable, but take some attention.
Supposedly the Starline brass was developed for ARMISPORT Spencers, but again chamber dim's vary.
The quality of Starline brass is very good.
I use CH4D dies and custom RMC cases with tightly fitting bullets that are barely crimped. No spinning.
I anneal after each use using the "salt bath" setup from "BallIstic Recreations" in ALBERTA!
CH4D can profile the case neck expander plug to match the taper inside the Starline case AND the sized bullet diameter. No spin.
The issue there is a SIZED (straight-sided) bullet being pressed into a tapered wall case that is tighter at the base of the bullet than at the mouth. This can change the bullet's fit in the barrel!
Ok, all cases have "some" inside taper in the mouth area, but Starline's taper may be enough to squeeze the bullet base or not hold the upper end of the bullet well. When the bullet is seated, it is gripped more at its bottom. Then, to seemingly tighten the looser mouth, too much crimp is imparted. The tight crimp can push the case mouth BOTH into the bullet AND set it BACK a bit, which EXPANDS IT OFF THE BULLET JUST BEHIND THE CRIMP! Hence spinning bullets.
But some here report acceptable accuracy with spinning bullets in STARLINE cases.
Ideally, you could have a fellow shooter near you give you five loaded, Starline case rounds.
If you are in the US, I can get some Starline, 35gr 3F Goex loaded rounds to you with HAZMAT shipping compliance, of course. Guess your location might make that a challenge.
Shoot them, wash well and send two to CH4D for a die set that matches both your chamber, case and sized bullet diameter that is approx .001" MORE THAN GROOVE DIAMETER for proper fit.
But, this usually take several months at CH4D.
My suggestion is to find out which chamber the RCBS dies are for and if for an ARMISPORT, try them.
Check bullet DIAMETER for bore fit, case tightness and accuracy. If ok for you, enough said.
If problems, let us know and if you want my test rounds, share here and consider calling Dave Davidson at CH4D.
Very respectfully,
El Supremo/Kevin Tinny