Yeah, the 160 TSX develops more pressure than some other bullets, despite the grooves in the shank. I've used 46.0 grains of H4350 in my 21" barreled 7x57 for years with various 156-160 grain bullets, and never had a problem, but the 160 TSX will get touchy with that powder charge in warm weather. (Yeah, H4350 is an Extreme powder, but even those still develop higher pressures in temperatures much above 70, though not to the extent of "standard" powders.)
Loading the 7x57 isn't like most other rounds, due to the varying throat dimensions of different barrels. My present rifle is a custom, chambered with a reamer with a short throat. It will still chamber and shoot any factory ammo I've tried, but doesn't require as much powder to reach the same velocity levels as some of the dozen other 7x57've I've owned, and pressures would definitely be too high with some of those loads.
Plus, as somebody already mentioned, the whole point of the 7x57 is a relatively mild-recoiling rifle that will still neatly kill big game. Believe it or not, a 140 at 2800 or a 160 at 2650 will do that, even on very big animals. I haven't done a Bell and shot elephants with mine, but have used it on good-sized Canadian moose with no problems, and also on African springbok (a little smaller than pronghorns) at just under 400 yards, both with 160's at 2650. Have killed a lot of other game with my other 7x57's out to 400 with 140's at 2850 or so.
If you want more velocity from a 7mm, buy a .280 or .280 AI or some sort of 7mm magnum, instead of pushing a 7x57 hard. It works just fine at moderate velocities, which is why it's still seen in hunting camps 121 years after it first appeared.
I've never grasped why shooters who want magnum velocities from a standard cartridge. Any thoughts to share on this?
The three responses above are the most pertinent presented. I will point to another J Barness article where he touted 2700 as the magic muzzle velocity regarding bullet performance as well as providing reasonable trajectory. I think everyone trying to squeeze an extra 100 fps out of a hunting rifle should read it. The real lesson of the article was his pictorial comparison of the 308 loaded to approx 2700 fps to a 300 mag at longer ranges . The trajectory drop delta was not near what many would expect and imho really exposes the folly of pushing the pressure envelope trying to get an additional 100 fps out of an already adequate cartridge.
