I used the Hornady gummy tips on a big whitetail buck, then a 150# hog. I was disappointed with the performance (lack of penetration and the bullet came apart) on both.
I have had good results on whitetails with the Rem 405 JSP over a slightly under max charge of H335. There is no lack of penetration with these and I have yet to recover a bullet, or have a deer go anywhere after being hit with one.
I have two Marlin 45-70s, a 1975 vintage 1895, and a stainless guide gun. The older gun I've had for 20 years, it's microgroove and I never found an accurate cast bullet load for it. I am hoping to shoot cast bullets in the guide gun. I've never used 300's except for the Federal factory load, which is a very good mild hunting load.