257 Ackley Improved

[coyotehunter4]

I just picked up a 257 AI on a Mauser 98 action. I was curious if anybody had worked up a 257 AI load with 8208XBR? I really like 8208 but the burn rate maybe a little fast for the 257 AI, just wondering if anybody had experimented yet?

 

[kludge]

You should head over to Shooters Forum - A shooting sports community and ask this in their wildcat section.

 

[coyotehunter4]

You should head over to Shooters Forum - A shooting sports community and ask this in their wildcat section.

Thanks wasn't aware of that forum.

 

[Broom_jm]

8208 XBR is between H335 and H4895 on Hodgdon's burn rate chart.

Burn Rate

Both will generate excessive pressure in the 257 AI at 80% fill rate, or less. That means it's not "a little too fast"...it's WAY too fast, to get best performance out of a Better (Improved) Bob.

Do right by your rifle and get something considerably slower. Either 4350 is a good choice; H4831SC is even better, if you're looking at some +P type of loads. The 257AI, in a strong bolt-action like your Mauser, can be pushed very close to 25-'06 performance levels. I'm not saying you need to go all the way to the 58,000psi +P+ loads, but you can certainly be up in the ~55,000 range, with that action and new brass.

 

[coyotehunter4]

8208 XBR is between H335 and H4895 on Hodgdon's burn rate chart.

Burn Rate

Both will generate excessive pressure in the 257 AI at 80% fill rate, or less. That means it's not "a little too fast"...it's WAY too fast, to get best performance out of a Better (Improved) Bob.

Do right by your rifle and get something considerably slower. Either 4350 is a good choice; H4831SC is even better, if you're looking at some +P type of loads. The 257AI, in a strong bolt-action like your Mauser, can be pushed very close to 25-'06 performance levels. I'm not saying you need to go all the way to the 58,000psi +P+ loads, but you can certainly be up in the ~55,000 range, with that action and new brass.

Thanks for the input. I picked up some H4831SC and am going to start with that. This is the first wildcat round I have worked with and published data is hard to find. Have got my cases fire formed and starting to try some improved loads. Thanks again for the help.

 

[Broom_jm]

Thanks for the input. I picked up some H4831SC and am going to start with that. This is the first wildcat round I have worked with and published data is hard to find. Have got my cases fire formed and starting to try some improved loads. Thanks again for the help.

Glad to be of assistance.

When working with an AI cartridge of any type, the standard process is usually to consider middle charges for the standard version your MIN charge, and work up accordingly. It should also be noted that a lot of the increased velocity you get from AI rounds is not necessarily from the increased capacity, but from higher operating pressures. However, the straighter case walls tend to grip the chamber more tightly, resulting in less back-thrust against your bolt or breech. Some folks feel you can run those higher pressures, because of this. That is debatable.

To complicate matters, SAAMI spec for the 257 Roberts (and the AI version) restrict pressures to 51,500psi. It has been widely accepted for years that modern bolt-action rifles, chambered in either cartridge, can safely run a bit hotter than that. I'm not suggesting you do so, but +P and +P+ load data exists for this cartridge.

The good thing about the H4831SC powder is that it meters very well and has a very consistent volume. Also, it's slow enough that you just about can't get in trouble with it, when loading for a strong action and 257AI rounds. Expect best accuracy with nearly full cases, or even slightly compressed loads.

 

[Water63]

That's a old cal I had one years ago I ran H380 if I remember right behind a 75 gr bullet. Can't remember if it was a Sierra or a Hornady. Fun cal to play with. Good luck.