Thread: 22-250 Ackley Improved Load Development

I recently got my hands on a Remington 700 308 barrelled action as a donor for a new build. Got it cheap 2nd hand with a Timney trigger already installed and sent it off to TrueFlite who trued up the action and re-barreled it in 22-250 Improved. I opted for a 28" long 1 in 7" twist barrel to allow me to shoot the very-heavy-for-calibre bullets at (hopefully) silly speeds. Gunworks have also made a 6" suppressor for it, to save my eardrums should I take this thing hunting (yes, it's going to be a mile long). I snagged a box of Lapua 22-250 brass plus some Hornady 88gr ELD-M's from them at the same time, plus I ordered a set of Lee dies.

The process of fireforming in an AI is pretty neat to see. Put in a plain 22-250, pull the trigger, and the case comes out looking very different - much straighter - with a 40 degree shoulder and more case capacity. But you need a near full pressure load for this fireforming to work properly. There's none of this "start low and work up" bs... You just jump straight in at (or very close to) max charge for the parent cartridge. I had some 50gr Z-Max bullets to use for fireforming and a good amount of BM2. The published "max" is 36gr so I decided I'd go with 35gr and load a few up. Case prep was a simple matter of running the new brass through a standard 22-250 Lee collet die and giving them a light chamfer to straighten out the ones with dings in the necks and set a nice consistent tension. To give myself an idea of whether 35gr was sufficient to fireform properly, I got some Sako 22-250 ammo from GC to use as a baseline.

TrueFlite sent me a pic of the rifle...



... and sent it back down to Gunworks who got to work fitting the can. Once done, I collected it, took it home, threw a VX5 on it, and hit the range the next morning.

First group was with the factory ammo (55gr SP rated for 3610fps from a 24" 22-250). Velocity from the AI was 3475. This was to be expected, as with a larger chamber, pressure drops. Fireforming also soaks up a fair bit of energy too. Next up: the Z-Max, and they chrono'd at 3650fps with an ES of 6fps and a sub half-MOA group. I could go to 36gr, but the new shoulder felt just as sharp as those on the factory Sako cases - and the load's seriously accurate and consistent - so we'll leave it at that.

Tbc...