Hey all, a new member and poster here. I just bought 8 original boxes of 7x57 ammo made by Kynoch. All in original boxes although the boxes are falling apart. Each has 50 rds in 5 round stripper clips wrapped in thin paper. Headstamps are all " k 37 7m/m ". Boxes are further marked " 140 grs solid pointed bullet nitrocellulose powder". From what I've gleaned off of this and other sites, I think these were manufactured in 1937, and have the copper nickel plating on the bullets. A random sample that I've checked appear to be in good condition, no corrosion anywhere and uniform color for casings and bullets. There are no colors I can see on either the tips or around the primers.
Also, the primers appear to be the same color as the case, in other words they don't look like copper primers. I suspect these are corrosive but thought I'd ask your opinion. Are the bullets themselves steel or steel core, or just lead clad in copper nickel. Also, in general are these safe to shoot in a 1910 vintage Mexican Fabrica de Armes mauser? Receiver is in good condition and has a replacement barrel/chamber. Opinions are all over the place, and I'm not looking for a definitive answer, just want to know if this is able to be used for general range use without ruining the gun or putting the shooter/ others at risk. Thanks for any thoughts.....