I have RCBS cast, gas checked 200gr bullets now need data to get started shooting my 71. Can anyone help? Thanks

Try 40 grains of IMR3031 to start.

I have a copy of a spreadsheet that someone prepared with a lot of published 348 loads for jacketed and cast bullets. PM your email address and I can send you a copy.

My Lyman Cast Bullet Handbook (although agreeably very dated) lists these loads for their 187-grain projectile in the Winchester 71. I would think you can extrapolate.

20.0 to 23.0 grains of 2400
20.0 to 30.5 grains of IMR 4227
25.0 to 35.0 grains of IMR-4198
35.0 to 47.0 grains of IMR 3031

I hope this helps...