257 Roberts Ackley Improved

pappyhat

I recently came into a Ruger 77 ultralite chambered in .257 Roberts. I was thinking of taking it to a local gunsmith and having it re-chambered to the .257 AI. Does anyone have any opinion on if this is a good move or not? How about the match of rifle to the new chambering? Finally, what is a reasonable price that I can expect to pay?

pappyhat

I recently acquired a Browning A-Bolt which has been rechambered to 257 AI. I would like to use this for coyote and smaller varmits. Any suggestions on 1st fireforming loads which would be used on varmits and then loading the Improved cases to its new capabilities. I have will be using new Remington cases.

Mobuck

I experimented with the 257 AI a little and read up on the conversion. My loading manuals suggested using a mid to upper end load with a 100 grain bullet and IMR 4895. You will need to determine if factory brass will headspace properly in the reamed chamber before beginning. The casehead must be held firmly against the boltface during fireforming or the shoulder will not be right and the primers will back out. Unfortunately, the one I have was botched and requires an extra step in the process to prevent this.

nononsense

pappyhat,

If the Improved chamber has been cut correctly, it's a simple matter of using the standard .257 Roberts loads with a bullet of your choice and go shoot. Since the case will expand to conform to the larger Improved chamber the pressure will be lower anyway. That's why many folks just use factory cartridges in some situations.

When I fireform, I am usually sighting in a new scope or I go varmint hunting so at the end of the day I wind up with some formed cases. You can also use a small charge of fast pistol powder with corn meal over that, separated by a small square of TP and topped with a wax plug for fireforming.

Once you have cases it's a matter of picking appropriate bullets and powders to begin load development.

Best.

22hipower

I have a 1903 Springfield rebarreled to 257 AI. I just fire factory 257 Roberts to fire form the brass and then reload as AI. Works fine and the gun is MOA or better with factory loads and the AI reloads.

Hawkshaw

Hey pappyhat---Look in the Nosler No. 6 manual under the 280 Rem AI. (or other AI). They show there recommended procedure there. It has always worked for me. HAWKSHAW

joel_black

The whole point of Ackley's improved chambers is that they can be shot with factory ammo assuming they are properly cut. I still have a Mauser sporter in .257 AI that I got from him in St Lake City. If anything, over the years, its accuracy has improved as bullets have improved.

pappyhat

Thanks to all for the info. Anyone have any favorite bullet/powder combos that works for them. I'm thinking of staying with the 87 gr bullet. I'll buy a few different brands of bullets and powders and start to work up some loads . Any other suggestions/comments will be appreciated.

Michibay

Along this same line...I have a Rem 722 that has been rechambered into a 243 Page Super Pooper. I fire factory 6mm Rems and they fire-form into the 243 PSP's. Have Fun!!! The 257 Roberts should work fine.

sandwarrior

quote:Originally posted by pappyhat
Thanks to all for the info. Anyone have any favorite bullet/powder combos that works for them. I'm thinking of staying with the 87 gr bullet. I'll buy a few different brands of bullets and powders and start to work up some loads . Any other suggestions/comments will be appreciated.


H4350 or VVN160 or Re-17 or RE-19.

pappyhat

Thankyou, I'll try a couple of those, most likely the H4350 and R-19. Any suggestions on other varmit bullets other than the 87 gr that you've had luck with ? Thanks for your time...

sandwarrior

pappyhat,

75 A-max's! Awesome little bullets just made to make that cartridge sing. Also, 90 hpbt's. Nosler 85 gr. BT's shoot outstanding as well.

If you want to do a little experimenting, Wideners has Berger 72, 78, {82}, 87, 95 and 110 MEF's for sale. These are discontinued bullets by Berger. But, they are benchrest quality and varmint slaying little monsters.

For loads, just find the starting point {for that given weight} in any book with .257 Rob AI info and work up. If no AI info use the midrange of the standard case for a starting point. Easiest way then is to run a ladder. Remember you aren't going to see pressure signs until they get way high with this cartridge. chrono'ing is a good way to go. And, careful inspection of the heat line on the bottom of the case is another way. Primer flattening needs to be looked at extra carefully because it doesn't happen as soon as with with cases that have more taper. AS SOON AS YOU SEE IT THOUGH GO BACK TO YOUR LAST ACCURACY NODE. Because at that point you are already too hot.

I know that originally, Ackley's whole intent was to get more out of the same length parent cartridge. But what came along and isn't really pushed by Ackley shooters, is that by finding that accuracy node, you save your barrel some from shooting at max pressure and....the biggie....you save case life dramatically. Longer case life means longer accuracy with the same bunch of cases. Much, much less stretch and therefore less chance of incipient case head separation.

-good luck, and let us know how it works for you (give us a range report)