Home Forums Hunting & Shooting Custom Rifles & Wildcats 243 AI questions

Been digging up some new rifles ideas the last couple of week.

Ran up on a sako L579 in 243 that has been “Ackley Inproved”. As I understand it they neck down the cartridges to allow for more powder (hotter load) to it will have better speed.

Questions:

- is any work actually done to the action? I may build off of it down the road
-can it shoot factory loads if I get tired of reloading?
-would rebarreling take it back to a 243? Or another caliber if I chose ?

An “Ackley Improved” cartridge is identical to the parent cartridge except with reduced body taper and increased shoulder angle. At equal pressures there’s limited gain in performance and increased brass prep because fire forming is required.

An advantage of Ackley improved cartridges is reduced brass trimming.

All told I don’t have any rifles chambered with an Ackley chamber because it’s not worth the extra effort.

No work is done to the action.

Yes, you can shoot factory ammunition from an Ackley chamber. All “proper” Ackley chambers will chamber the parent cartridge ammunition. This will make Ackley brass. You could then reload the brass and it would match your chamber.

A rebarrel will revert back to the parent cartridge or any short action standard bolt face cartridge.

Some of the older/tapered cases (250Savage Improved, 257 Roberts Improved, 30-30AI) see a good increase, but the 243 has a modern case shape.

my buddy did a build on a sako action, he said they have a lot more flex to the action and aren't that great of a platform for custom builds especially those with very heavy barrels.

If I rebarrel it will be back to a regular 243 or possibly a 7mm08/260

Fire forming is no big deal, just shoot standard ammo, it will fire form to A.I. then resize neck and go on and reload, it's no big deal. Rio7

My opinion too. My 250ai is a laser with 85gr Barnes X bullets.

Your "buddy" is wrong.

If you look at the amount of steel on the bottom of the old Sako actions ... they are stiff.

You'll gain right at a 5% increase in powder capacity which translates to perhaps a 1.5% increase in velocity at same pressures. Assuming 3000 fps for the parent case that gives 45 fps more, hardly worth writing home about. Rate of throat erosion will be reduced by around 10% which is good considering the .243 eats throats. You will also rarely if ever trim cases. I trimmed a batch of cases right after fire forming and over 25 firings they never needed trimming again. When I finally tossed them at 25x they had only gained around .005-.006" in length.

Getting back to the velocity increase. Lots of AI shooters claim greatly increased velocities because they load to higher pressures. In the .243 I think that might be somewhat valid. The .243 shows a wider variation in pressures in a given string so it's max pressure was lowered some time ago. The 40 degree shoulder of the AI tames that bad habit so one could load back up to the original pressures. Doing that combined with the velocity increase provided by increased case capacity could net you maybe 75-100 fps more. That's just theoretical discussion which I wouldn't personally condone unless you know the pressure specs of the original loading, have very good pressure testing equipment and know how to use it.

But the increased throat life and lack of trimming are the main benefits for the .243 AI.



Now all that said, I've had two barrels so chambered and if you like to mess around with such things they're fun and something interesting to work with. I certainly learned some things as a hobbyist so they were worthwhile projects. If you just want practicality get a 6mm Creedmoor and be done with it.

Your buddy has no clue what he is talking about Sako is one of the better factory actions for a custom build, I have several including an L579 that the OP is asking about.
The 243AI gains you very little compared to other Ackley chamberings because you are mostly changing shoulder angle, the body has very little taper to start with.
Never really found the claim that Jim in Idaho makes of increased throat life to be valid in any of my Ackleys but less trimming for sure
As for the OP's last question, yes you can rebarrel it back to 243 or any cartridge you choose that has the mythical .473" bolt face, The L579 is a short action so you could go 22-250 to 308 and still use the magazine

An important consideration when rechambering from a standard to an Ackley chamber is the need to set the barrel back, usually a complete thread so the writing, sights, etc. are all facing up. If the Ackley reamer is run in until the old chamber is cleaned up there will be excessive headspace when firing factory ammunition. The go gauge becomes the no-go gauge & if a go gauge is required will be approx. .004" shorter than the standard go gauge.

I have to smile when people that have never owned one regurgitate what they've read or heard. I've worked extensively with 4 different Ackley chamberings & each one has been just a wee bit different. Two of them (257 Roberts & a 30-06) fireformed factory brass without a hitch. The 3rd one (338-06) even though chambered properly as noted above refused to do so, developing that bright ring at the web that tells us the base will soon separate from the body. Brass was successfully formed with 16 gr. of Unique, a case full of cornmeal & a wad of TP fired straight up into the air in the backyard. I dont know why, but it's how that rifle worked out. This chamber is a tad rough... bolt lift is fine but extraction isn't so good, so that could be part of the problem.

The 4th (22-250) was a trade-in & apparently just had the reamer run in to clean up the chamber (& then some) giving somewhere between .020 to .035" excess headspace. Brass was partially separating on the 1st firing, so now is expanded from .22 to .25 then resized in a standard 22-250 die with a secondary small shoulder to chamber very snugly & fired with a stiff standard 22-250 load. This one is not a true Ackley. It's an Ackley long maybe. Using Ackley dies kept way off the shellholder I'm just now retiring some 30 year old brass that was loaded 10 or more times (a 53 gr @ 3975 fps), that's finally age-splitting necks. Primers still fit snugly.

I like all of my Ackleys & run them on the warm side, because that's what they do best. If primer pockets stay tight for 4-5 (or more) firings it works for me if the accuracy is good.

Jeezus Fhuqk,you CLUELESS Droolers are a hoot! Hint. Congratulations?!?

On the presrcibed platform,I'd go Seex Kreedmire and at least 8" RPM. It's too trite in COAL,to make a 260/260AI or 7-08/7-08AI shine and likely outta room in 243/243AI(though certainly suffering a Retard Twist rate). Hint.

Rest fhuqking ASSURED that a 250AI with an 85gr of any flavor,is certainly no "laser",with the schit aero form and pedestrian velocity. Though in fairness a 224 Speedmire stoked with an 88 ELD and it's .585BC at 3200fps,most certainly is. You gals will haveta' pardon my shooting it all and then some. Hint.

There is no "extra" "effort" required with an Improved case. They utilize a like number of ram strokes to load,which will only come as a "surprise" to Drooling DUMB Fhuqks. Hint.

You Magnificently STUPID Fhuqks,never disappoint,by simply doing your best. Hint.

Bless your hearts for trying though.

Hint.

LAUGHING!............

What 'Stick said.

I have a 243 AI with a 8 twist and 350 formed and loaded brass, and it wasn't rocket science to form the brass.

I also agree that if I were to do it again, I'd just go 6mm Creedmoor.

I have shot the 243 AI since the mid 80's. Today, I would go the 6 Creed, and Stick is spot on. Get the toughest brass there is....pick. Spend some time on throat geometry design.

Many wonder what the 243 AI will do. I hunted coyotes with many 243 AI's. 70g Nosler ballistic tips at 3800 shooting tiny bug holes is normal, not the exception...zero freebore reamer left room in the Remington magazines, barrel set back at 1700 rounds if you use ball powder, otherwise, no.

I fire formed killing stuff, 70g Noslers at 3700.

Keith went through a whole sh#tload of barrels too.

As another post said, the chamber in that 243AI needs to be checked for headspace, as some gun mechanics would just run an Ackley reamer in without setting the barrel back to achieve correct (tighter) Ackley headspacing, at least with rimless case rounds. I’ve had a few Ackley rifles and enjoyed tinkering with them. It helped to have my own machinery (lathe). I have kept a favorite- Shilen barrel 250 AI, a favorite of mine.

The .243 AI rifle the OP bought was one I bought from a campfire member back in 2013. I went back through my records and this is what the original owner said about the rifle and the smith that did the work on it'

"Action is Sako's L579 and the barrel is a Sako sporter take-off re-chambered by Larry Cribbs of La Grande. Twist rate is 1-10, barrel length is approx. 23" muzzle to chamber, muzzle diameter is .640". Stock is a lightweight Brown Precision with a 14 1/4" length of pull and krylon earth color. Stock trigger, no sights."

Larry Cribbs competes in and builds rifles for NBRSA so he did a precise job on the barrel and the smithing. Whoever did the stock work was less talented but the rifle shot very well so I left it alone, I had never owned a Sako before so it scratched an "itch" for me. I reloaded for it and it came with 80 fireformed brass and 20 new cases and Redding 243 ai 40 degree dies. The OP doesn't reload and didn't want the dies or brass. I pretty much only shoot, .22, .223, and my Dad's rifle for hunting nowadays so I didn't use the rifle like I planned to and sold it. I would be surprised if the rifle doesn't do fine with factory ammunition before the OP eventually re-barrels it which he said was his longer range plan for it. That said, I have a .223 AI that was smithed by I,T, & D and with some of the re-manufactured ammo based on military brass the cases will show incipient case-head separation. It fire forms fine with factory new ammunition and I get good case life.

A big area of concern is remaining barrel life on that Sako... how many rounds were sent down that barrel.since barrel life on a 243 is relatively short. Another concern is twist rate.

Otherwise it might be better to invest in a 6 Creedmore.

I built a 243AI back in the day as well, great accuracy and fire forming was very accurate as well, so you could hunt while fireforming, win/win.
Now I would not build another one, just buy or build a 6mm Creedmoor and call it a day.