6.5x58 port or mauser

Looking for starting loads for my 6.5x58 portuguese or mauser. I will be shooting cast bullets only.

Welcome to The Guide.

What bullet weight(s) are you going to use?

For 140gr bullets I would start at around 21gr of IMR4064, 20.5gr of IMR3031, or 21.5gr of IMR4895 and work up from there in 1gr increments. A chrono is a must because data is virtually nonexistant - you'll have to treat it like a wildcat.

According to COTW, 140gr jacketed loads for the round max at around 24-2500, so depending upon the alloy I would say you can realistically push cast of that weight up to 2200 or more, but where the accuracy node(s) might be is up to the rifle. Internal volume is very close to the 6.5x54M/S and 6.5Carcano, so you can use the reducing formula for medium capacity cases on jacketed data for either with IMR or other extruded powders. (JacketedMAX - JSTART = DIFFERENCE, JSTART - DIFFERENCE = CastSTART) NEVER use this with a BALL POWDER. Data above was generated this way from listings in the Sierra manual for the 6.5x54M/S with 140gr bullets, a round I shoot with both 140gr and 175gr cast bullets.

I am not a big fan of using pistol powders for cast rifle loads, but that is solely because I am after hunting loads, not plinkers. If you don't already have a copy, get yourself Lyman's Cast Bullet Handbook. That will give you a better idea of where to start.

Thanks for the info. The alloy hardness will be between 12-15 and gas checked. One of my all time favorite powders that you listed is IMR4064, that was used in a Winchester Mod .270, when I first started handloading in the 1970's. I had a hard time identifying the caliber because of the lack of caliber markings on the barrel. It was built as a sporter in the Manlicher style around 1914 and marked 6.5 P.P. on the left side of the barrel. I did a chamber cast, ordered a couple of cases, loaded 10gr of Bullseye topped of with corn meal and a wax plug, and fire formed them. Then I had them verified.

Thanks again ...

Any chance you could post a photo of the rifle? I'd love to see it.

What mould is it?

I opened a new thread with a picture you asked for. Hope you like it!