The .257 Marksman (25 western)

[SloppyJ]

That's on par with what I've experienced. Pretty much my rule of thumb anymore is if I find pressure on new brass I expect to drop the charge 1.5gr on formed brass to be completely safe. It's just not worth riding the ragged edge and 50fps doesn't functionally do squat.

That mistake was completely on me and a bit frustrating. Good rule of thumb for sure. I was just excited to load them up and go shoot it in different scenarios. That backfired on me.

A little pissed on the brass, ive stepped all over my 300prc lapua cases and havent blown out primer pockets but thats the life you choose getting into the wildcats.

Its fun chasing the top edge of speed but you're absolutely correct, there's no benefit to it and it causes a lot more problems than the extra 50fps or so you gain.

 

[WKR]

@WKR

What lead you took so this instead of a 25-7 prc or some other magnum variant?

Like stated above,
I prefer short action cartridges and wanted to try something new.

Also the diminishing returns starts coming into play with the 7prc case in my opinion, and the 35° shoulder on the western parent case is a small plus.

 

[SloppyJ]

Got some more load dev in over the weekend. I bought a jug of N570 that will be dedicated to this barrel and continued down that road with a bunch of 5 shot groups.

64.5gr - 2935fps
65.5gr - 2977fps

Honorable mention:
66gr - 2994fps ES-10 and SD-3.9

64.5 is the plug and play charge. 65.5 is also very good but the ES/SD on the 66gr load is worth some seating depth testing for me.

Thought I'd share the latest but she's just about dialed in and ready to go. Who else has built one at this point?