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...

Almost too easy, right?



Next up, some 50gr Barnes TTSX. I have a handful of these and figured that at close to mach 4, they'll be as good on wallabies as they'll be on pigs and fallow. And there's no risk of them blowing up from the insanely high speed and rate of spin. Out of curiosity, I used some Federal 243 brass that I sized down to 22-250 AI (mechanical forming vs fireforming) over some AR2208...



I also wanted to try some 69gr TMK's, as these have always been an easy-to-get-to-shoot bullet in 223 and I have a feeling the 88gr ELD-M's will require some seating depth testing. I went for a much higher charge of a much slower powder...



No slouch!

My plan is to use the Lapua brass for the 88gr ELD's but I haven't got much of that fireformed yet. Even so, I can use some of this Federal 243 brass to give myself an idea of what kind of charge weights I'll need to be using. I picked N160 and had high hopes...



A little disappointing. Speed was 3190 with an ES of 33. The vertical stringing suggests to me it's in between nodes and either a little more or a little less speed should tighten it up. I think N160 is just about topping out though so next to try will be AR2217.



What was interesting was how different the case lengths turned out after fireforming. The Sako cases (left) shrank quite a lot from about 1.910 to as little as 1.868 after firing. The Lapua brass (centre) did not shrink as much. Whilst my Federal 243 brass (right), not ballooning out like the others, grew about 0.002". I shall have to see if I can encourage the Sako and Lapua cases to stretch a little further so that there's not a huge gap between the end of the case and the throat.

Another quick range visit.

Don't have enough of the Z-Max to fireform all of the Lapua brass, so I loaded a few more with 50gr Nosler BT's using a max 22-250 load of Benchmark 8208 for a nice increase to 3775 fps. I tried them with the same 35.0gr of BM2 as well and whilst the speeds were within 10fps of the Z-Max's 3650, the groups were not. Seems the rifle might not like these bullets as much and more experimentation is required.



But the main reason for the visit, was to try out the 88gr ELD and AR2217 combo, now that I had some fireformed Lapua cases. I had tried to model this in GRT beforehand so that I wasn't flying completely blind...



... Looked promising. But GRT rarely matches perfectly with reality without some tuning, so to play it safe I made a workup starting from 41.0gr up to 45.0gr, with 4 rounds at the two charges where I guessed (hoped??) I'd find some success. This was done in 1 grain steps to confirm safety whilst also minimising round count and fast forwarding to where the speeds should start getting interesting. I also extended the overall length to 2.670" after measuring to find that my "jam length" is 2.688".



41.0gr clocked 3024 fps and 42.0gr clocked 3086 fps. Neither showed any pressure signs, so I was good to push on. The POI's of the warm up shots looked reasonably consistent too which was promising. I dialled up 1 MOA and got a split group at 44.0gr with it bouncing between two distinct POI's which told me this was a bad spot - despite a velocity of 3252 fps and an ES of 4!! 45.0gr looked like it might tighten up again, although with sample size of two I can't be certain - however I did start getting some hints of ejector swipe which says this is pretty much a max load. The chrono didn't manage to register either shot but it will have been just north of 3300 fps.



The clear winner though was in the middle at 43.0gr with velocities between 3160 and 3174 fps and a really nice little group.



I'm happy with this. A little less raw speed than I'd hoped for, but great accuracy and consistency, plus kinder to the barrel and brass given it's a fair bit lower pressure than N160 was.

I'm shooting 88 Eldms out of a 22 Creed which is fairly similar to 22.250 Ackley.
Found RL16 favorite powder, followed by 2209 & 4831sc.
RL26 might be another option, and is popular load in the States. I had some great results with it but then had carbon ring issues, probably to do with shorter barrel and suppressed.

You can probably get a wide range of powders to work fine, I use 4064 in my 22.250 with 69's.

Found they like a wee jump, like 30 thou in my rifle rather than jammed.

@jackson21, I've had issues with Re26 before too and with the cases coming out short on the 250, there's quite a gap at the front there for a carbon ring to build up. Re26 is probably therefore not a great idea. I'm happy to stick with the more conventional ADI powders which will get close without any of the issues.

Sierra have data for 22-250 AI which combined with Hodgdon's 220 Swift data really helped with powder selection. I've got all the barrel length to utilise slow powders and they provide very good case fills.

Yeah H1000/2217 seems to be very popular with the heavies especially 88-95's. I haven't tried it.

Varget/2208 or even 4064 for the lighter 65-75's seems popular choice also.

thos 50grn Zmax are great projectiles.....wallaby medicine in extreme....and thats only at .223 speeds.... they do naaasty things at std 22-250 speeds.
a fast twist 22-250 sounds like awesome idea if fella wants to run heavier projectiles....maybe the NBT were struggling to hold it together with all the extra G forces...

@Micky Duck, yeah I have high hopes for them. I think that at 4000 fps and 400,000 rpm even the TTSX will be pretty devastating. Will be heading down your neck of the woods this weekend to hopefully gather some results.

I think I've had one blow up so far and that was with a 55gr Nosler Varmageddon - another great bullet but maybe one not able to stand up to this kind of abuse. The BT's seem OK. Actually it might be an idea to use the VG's for fireforming given the speed will be lower and save the BT's for later.

When fireforming cases sized from 270 to 2506AI, I leave a little 'bump' at the bottom of the neck so that the case is held firmly between the base and the neck bump. The Fireform result is perfect and consistent. As an example of loads, a normal load for a 110 AB is between 3300 and 3400 fps. I load the fireform loads to 3000 fps and just go hunting. For a 22 250 an AB would work very well I think because they can handle and work at a high velocity just as well as at a lower with no blow ups

I'm getting a nice crush fit with factory ammo and the Lapua brass. The brass is shrinking down to about 1.875 Sako is shrinking +/- 0.007" and the Lapua is shrinking +/- 0.003". Some shrinkage is to be expected because a little extra material has to come from somewhere. The Lapua is proving to be more consistent though which I guess is down to higher quality brass and me accurately weighing out charges.

what is barrel fouling like?

yip I would be going hunting with std round and keeping the now fireformed brass.....no way would I waste projectiles to do it...
interesting reading about this cartridge all the same...the 50grn ttsx will be devastating...I have a dozen or so,heavy monos of different weights that you will be able to use and I cant as both my .224s have too slow of twist...I can leave them out for you to collect on way past if you like....

What's too heavy for your twist @Micky Duck out of curiosity? I haven't tried any in mine yet, it's on the list though.