When they first came out, I tried the Nosler 300gr. PAR in my Ruger #1. It's now my primary #1 .45-70 load for hunting.
With a MAX charge of IMR4198, I get a chronoraphed 2180 fps out of that little 22" barrel.
This load is safe in the #1, the Marlin line of .45-70's and similar rifles/carbines but NOT in any of the older or weaker actions. I have a new model 1886 Winchester take down and was advised not to use it in this rifle. ??? It hits hard on both ends.
When I spoke with Nosler tech support on the phone about this load, they said it was safe in the #1 because, "the sky's the limit with the #1".
Accuracy at 100 yds. is generally around an inch from my #1, sometimes an inch and a quarter. I've had 3-shot groups that have all three touching when I do my part.
I feel this load adds maybe 50 yds. to the lethal range of the .45-70 on deer size game. Maybe black bear also.