The 3 savages I have had experience with all had decent looking bores, a heavy barreled 112 in 22-250, a 110 in 300 win mag with sporting contour barrel, and a model 10FPS in 308 win. All three were good Shooters, but the heavy barreled ones were better.
The 10fps is every bit as accurate as the rem 700p I am issued, but it's only been about the last 3 years or so since I was cleaning bores as I posted.
I used to clean the bore by taking by one piece bench rest 30 cal rod, and a brush, copper solvent, and caliber specific lathe turned brass jag and clean until I could get no more copper out of the bore. Trying to establish a clean cold bore zero was a trial, and the best I could get was a 1" group, but the group was as much as 2 inch high and 1½" left of my cold bore point of impact, depending on temperature, humidity, and what-not. Since I've been cleaning like I posted, I guess it may not technically be a clean bore, but my 700p will hold ½" groups, and shoot to zero with only ½" of variance between my cold bore zero, and warm bore point of impact. This is with 168gr Hornady A-max TAP. The lawyers won't allow reloads. I also notice very little variance from temp or humidity.
I'm not sure about the velocity question, as the calibers I do this with are various 22lr, 223 rem, 7.62x39, 308win, 30-30, 45 acp, 45 colt, 45-70, 40s&w, 375 H&H, 410 and 12ga. None of which I would consider high velocity. And the accuracy level discussed is higher than what the average hunter needs.
Lawyers aren't after your retirement if you miss a deer's medula oblongata and it gets a shot off before it dies. In all actuality, 99.9% of snipers will never need to make that shot, but we have to train to it. And it is fun head shooting deer at 500 yards.
The point I believe the sniper that relayed that cleaning method to me was making is all barrels have a service life, and most shooters put more wear on their barrels cleaning them than they ever do shooting, with no real gain.
Also if you are set on a bore brush for your 45-70, make sure it is a .458 brush. If it says "45", or was bought at a dept store, it is probably a .452 brush. If it is in one of those "Universal" cleaning kits it is definantly a .452 brush.