Milsurp After Hours

Today I was zeroing a Spanish Mauser 7x57mm mauser and I noticed after firing the rifle the casings has a hole on the side of each casings identical to each other. I'm not sure if it's a headspace issue or gas pressure issue. I am not familiar with Mauser actions. The optic is a vintage weaver k4. If anyone has any advice, I greatly appreciate it.

Good to see a new member. As to the question. I'd imagine you know that the Spanish Mauser was originally configured for the 7x57. Then when the Nato round became the European caliber of choice after WWII many Spanish Mausers were then reconfigured to fire the Nato 7x62. The thought crosses my mind that you may be firing a smaller caliber bullet in a reconfigured larger 7x62 chamber. Look and see if there is a caliber marking on the receiver.

From the look of the stock what you have has been "sporterized" by someone... possibly a previous owner. In such case, could they have done anything to the chamber caliber? I wouldn't shoot anything further through the rifle until I had it checked out by some competent gunsmith.

I got to thinking about my Spanish Mauser and about the caliber marking. The 7.62 mark is there on the receiver on the side opposite the bolt handle

On the subject of Mauser ammo, the only two Mausers I have are both kind of oddball calibers.
1891 Argentine Cavalry Carbine in 7.65x54 originally, but now the modern ammo is 7.65x53.

1871 Uruguay Single Shot Long Rifle, sometimes called Uruguayan Mauser-Daudeteau or "Dovitis Rifle" in 6.5x53.5SR. (Semi-Rimmed)
This ammo is no longer available, you could buy some special made years ago, but no more. It hangs on my wall now.

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