i missed last night that you were using the hornady 230 XTP - i saw 230 and my brain went right to FMJ bullet - or i would have brought this to your attention sooner
i had contacted hornady about using the 250gr XTP (#45200) in a rifle (didnt mention the 450 specifically).
this was their response
i havent specifically inquired about the 230 XTP (#45160) yet but i would think it would stand to reason that this bullet was designed for terminal performance at or below that of the #45200 and as such really need to be used in rifle calibers very very carefully.
re: S&B primers
i got a brick of these back when components were still kind of scarce to test with in my 38 special and 40. they seem to be ok, but the cup dimensions were larger than cci small pistol primers. i had brass that i was having trouble seating some of them in - very tight seating by hand, even crushed a couple in the progressive - in that when i switched back to the cci's and the same lot of brass seated no problem. loaded behind power pistol with 125gr berry's, they did not seem to ignite as well either - the perceived recoil of the same charge wieght loads did not feel as stout as they did with the cci's in my little snubby LCR 38.
for 2 cents each they did ok, but i've relegated them to the back of the reloading stash to be used somewhere down the road, or even traded. i suppose at the very least they would be useful if i get some brass that the primer pockets start to get a little sloppy on.