I'm fixing to send one of my Winchester 94's (26" Canadian Centennial) out to JES to have it rebored to 38-55, 3 groove.

Any idea what chamber reamer he uses? I was gonna order some brass from Starline, but wasnt sure which length to get.

My rebore uses 2.080 length. And had to run a reamer so rounds would chamber. I fire lapped it also because a pin gauge would not go through. Don’t remember the size but after ten lap loads it dropped through. I ordered the five groove, shoots pretty good now. Nice cartridge in my old model 64. No action work was needed for flawless function

My 3 groove JES rebored Marlin 20" does great with Starline 2.082 length brass and bullets sized to .377. I started out with the Lee 38-250 mold, but later switched to an Accurate 38-250B four cavity, ordered as a plain base. Both have been really easy to get accuracy from.
I use 3 main loads, all with the same bullet at 10-12 Bhn.
10 grains Unique or Universal for a light plinker/practice load at about 1225 fps.
21 grains 4198 for a nice deer load at roughly 1400 fps
32 gr 3031 for 1600 fps and a substantial "whop" when it hits at typical woods ranges. This one I use powder coated bullets to help identify it as the heavy load. The others are pan lubed with Wind's Wonder Wax (50% bees wax, 40% Crisco, 10% Vaseline)
Wish all my projects had turned out as easy and successful as this one.