Home Forums Reloading Bullet Casting 350 Rem Mag cast bullet ???

I have a 350 Rem Mag that I have some 220.8 gr lead gas check bullets (originally 215's for 357 Max, dropped heavy) that I would like to develop a load for. The bullets have a BCN of 27-28. I am having a hard time finding a load for this paticular bullet. The closest I can come is a 220 gr jacketed load. With a bullet that hard can I download the starting load(of the jacketed bullet) by 10% and start from there or would I be risking a squib load??
Whats the best way to go about this?? Thanks!