I have three 7x57s , a model 700 remington, a 98 mauser built by mauser, and a bruno model 21 or 22 ( small ring mauser). I have not been able to get over about 2650 accurately with 139 gr hornady, or nosler ballistic tip 140 with any of them. and I have tried numerous powders such as IMR 4350 and H4350 4064 but none of the really modern ones such as big game hunter or RL17 etc. These loads were not really hot loads, but were full power loads, judging from extraction, look of primer etc. These loads were all extremely accurately averaging i inch or less for all power charges s I worked up. when they started opening up I backed off. but the chromo said 2600plus. I also have a winchester 70 7mm08 that I get 2850 from, accurately. I have sort of lost interest jn the 7x57 because I haven't been able to get adequate velocities from it.. Don't know what I did wrong. Its not as if Ill starve from lack harvested game as Im too much of a looney for that.
There is no reason why you should not look toward reaching 7-08 velocity in your 7x57. Of course much depends on what the throat length your rifle has but I have three riffles in 7x57. Two will shoot right along with the 7-08 and one, well I'm still trying to figure that one out. It's a custom that shows high pressure early on. For spits and grins I ran some of he last Hornady 175 gr. round nose loaded up to duplicate the 2300 FPS velocity of the original 1893 load. The Ruger #1A and M70 FWT did exactly that with great accuracy. The third, a custom based on an FN Mauser action went 150 FPS faster the the other two rifles. Chambering is very tight but necks measured after firing show plenty of room in the throat for proper bullet release. I talked with my gunsmith about the problem and he said he used the standard throat as used on the original Mausers, that is long enough for 175 gr. round nose bullets. So a short throat isn't the problem. I've even slugged he barrel and it's good there as well.
From the two rifles that are not having pressure problems I have can run a 150 gr. Nosler Partition at 2800 FOS with .75" accuracy at 100 yards with Re17. I have run the 140 gr. Nosler Ballistic tips to 2800 FPS using W760 again with .50 to .75" groups. Even the problem gun will run Winchester 145 gr. factory ammo into an inch. Maybe I should run some over the chronograph to see just what they do. First I have to find some. They're Unobtainium right now, aat least locally.
Paul B.
