Just got back my Marlin 36 after a little custom work by John Taylor. It was a scrufty carbine in 30-30 that was none too accurate and otherwise did not suit me. (BTW it was not a collector grade piece) Some time ago (maybe 20 years) I acquired a new in the grease Marlin 336 24" barrel. I sent the M-36, the barrel, a forend blank and the required hardware to convert the forearm from carbine style to the rifle style.
In due time the package arrived, and John had done a top notch job putting this project together! I had concerns about how the barrel would handle cast since it was a micro-groove type, but I should not have worried. I have used the RCBS 32-170, a 180 grain mold from NEI, and a 130 grain from NOE. The 130 grain is the most accurate with 16.0 IMR 4227, with some groups as small as .40" at 50 yds. The NEI and the RCBS like 18.0 to 21.0 Gr H 4198. Groups run from .75 to 1.25" at 50 Yds.
Dropped a tree rat today with the 130gr. Needless to say I am very pleased with the new toy!
I plan on deer hunting with it this fall using some 170 gr CIL bullets I picked up 30 years ago. I picked up 1K of them for $50. 30.0 gr IMR 3031 appears to be the sweet spot.