257 Rob AI

[GaryS]

Just got a barrel this last week for my encore. 22" MGM heavy factory contour with a 1:7.5 twist.
I'm working on a load and it had a great group at 43.5 grains of H4350 then opened up as I went higher. I got to 48 grains and it started tightening up. I stopped at 49 grains. My primers aren't consistently flat (fed 210M primers) and the gun opens easily and the cases slide out easily. The 49 grain load is slightly larger than I would prefer, but, I can live with it. I may also try some different powders in the future. Anyone running more than 49 grains of H4350 in this caliber? I looked at my 25-06 data and I'm only running 47 grains in it so I started getting nervous!

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[JeffreyDeGraff]

What weight bullet are you shooting?

I took my 257 Ackley to the range today, I am testing 117grSST with H4831. With this combination, in my rifle, 48.5gr was max, 49.0gr (which was the most accurate) gave me ejector swipes and a heavy bolt lift.

In looking through my notes, I tested IMR4350 with 115gr nosler ballistic tips, up to 44.5gr without any pressure signs.


JTD

[GaryS]

That would be helpful information! I'm using 115 grain ballistic tips

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[JeffreyDeGraff]

The nosler manual goes up to 45.5gr of IMR4350 with the 115gr BT. I tested up to 44.5gr. H4350 data should be close to IMR data

Like I said in my previous post. 48.5gr of H4831 is max for me with 115/117gr bullets.

Each rifle is different though, and even though my rifle won’t do it safely, doesn’t mean yours won’t either.


JTD