I have had several 7x57's. One was a BSA Viscount.
The book loads for the 7x57 are low due to the old rolling block rifles that might still be floating around. (Not the bolt actions.) For modern rifles I start with 7mm08 data. (And even then with the 8% larger 7x57 case, you will get less pressure)
With the 7x57 the throat will be different with each rifle manufacturer, some are really long (like Ruger) and others are not. Some you cant touch the rifling with a 140 grain bullet. So what is good in one rifle will be totally different in another.
I use AR2209 powder and with this powder you should be able to load up to 2850-2900 fps with a 140 grain bullet and a 22 inch barrel. So while using a chornograph Just keep adding powder till you get there. Most rifles will do it with 50 grains others may need more because they have a longer throat.
With a 154 grain / 160 grain you can get 2650fps.
I have reloaded the 175 grain round noses years ago at 2400fps. I dont think you can buy them anymore through.
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