Lee 429-255-SWC load data help

[oley55]

I am hoping to find something resembling published load data for the long time discontinued Lee Mold 90343, 429-255 SWC. Apparently Lee used this same number (90343) for a 401 mold at some point and it is now used for their 7mm-08 trim die. Older info discussion here: https://castboolits.gunloads.com/sho...7777-Lee-90343

It is plain based and as cast weight is 266 grains using COWW and is/will be powder coated. For now I plan to run it in a Ruger RH.

I am mostly flailing around trying to nail down COAL and starting loads and thought perhaps some load data is to be found in some older cast bullet reloading publication/s or possibly in 'The Complete Reloading Manual for the .44 Magnum'.

If I seat to the crimp groove there is a LOT of bullet stuffed deep into the case with a 1.605" coal. If I seat at the first of three shallow/narrow lube grooves I get a COAL of 1.710". Held beside a Keith style bullet, at the lube groove the amount of seated bullet is quite similar and it still plunk chambers in my Redhawk (but not in my Dan Wesson).

Since I have most of an 8 pound jug of IMR4227 sitting around without a mission, I plan to start with it. If that doesn't pan out I have limited quantities of H110 and Unique.

FYT, I posted a similar request for information on the firingline forum.
edit: added bullet pic alongside the Keith style, RCBS 44-245-kt, as cast 249.6 grains, with COWW.
edit @: updated pic showing both 1.605" and 1.710" COALs.

[45-70 Chevroner]

My Lee Second Edition manual has a starting load for H4227 of 20gr for a 280gr Jacketed bullet with a velocity 1215 fps. I think you will be ok with that load in your Red Hawk. The seating depth you used for the plunk test in the RH will be fine. The max load is 22gr.