Hey, just a quick question on Ackley Improvement. I have a Model 7 in .243 Remington with an 18.5� long barrel. Will I gain anything by Ackley Improving the chamber? I�m thinking in the short barrel length that I will not be able to exploit the extra powder capacity of the AI. Please advise. Thank you.
Bill

If all you are looking for is a velocity increase with that short of a barrel, I think you will be disapointed.
Putting a 20 - 21 inch barrel on the gun will likely get you as much velocity with the same pressure. And may not cost anymore if you use a takeoff barrel. The 700 take-offs may work - not sure though. The AI die will not be cheap either.

On the other hand, If you want to play with a wildcat and learn lots about reloading with the added advantage of little case stretch -go for it.
Been there, done that and learned a bunch.

To be chambered correctly for an AI (will also shoot standard ammo)the barrel must be removed and part of the threaded end removed/recut, then cut the AI chamber.

Might want to consider the 6mm-284 as an alternative. Or rebarrel with a longer barrel.

[ 11-13-2002, 06:17: Message edited by: trigger ]

I'll do the quickload for you, to let you know the gain

at 55k
243 win
MAX 2855 fps

at 55k
243 ackley
MAX 2883

28fps? not worth it, to me.

jeffe

I am real dubious about the benefits of "improving" most fairly modern cases such as the .308 family, particularly in short barrels.

It works wonders in older cases with considerable body taper. I happily shoot a .267 AI and a .25-35 Improved. They seem to give me 200-300 more fps than the standard versions. But they also have a much greater increase in case volumn than you could get out of .308 based cartridge.

I would expect pretty good results improving 7x57 or .250-3000, too.

Correctly done, the factory cartridge headspaces on the juncture of the neck and shoulder for fireforming. In order for this to happen the Ackley Improved chamber is cut with .004" negative headspace on a standard go guage. This is the correct way to chamber the AI cartridges. So to rechamber a standard barrel it must be set back a bit if it has no sights and one full turn if it has sights.
There are some illustrations in current reloading manuals which show incorrect dimensions for some of the improved cartridges but I don't think the 243 is one of them.
I feel that you would gain absolutely nothing by rechambering your existing barrel. Regards, Bill.

Bill, I missed something.

If you ream an Improved chamber in such a way that the reamer never touches the juncture of the neck and the shoulder, why do you need negative headspace?

I'm not saying that you are not right, but I sure would like to know why?

Leftoverdj,

Go to page 4 of the gunsmith posts on this site to the date 10/30/02 under the heading "AI fireforming and headspacing". There is a wealth of info waiting to be read regarding why barrels require set back to correctly set up the Ackley chambers...

It will make for some pretty good reading.

Regards,

Malm

It'll be louder,thats all.

I rechambered a 24" barrel to 243 AI. It's been interesting, and I've learned a lot. Did I get any fps gain? Not really, my accuracy load is about 50 fps faster than it was.

Thought about doing this to my .223.
Get real tired of trimming cases. That's the only reason for me.

I'm a proponent of the "Improved" case designs and dote on the 243AI in particular. That cartridge offers more capacity than the 6mmRem,is more mag box friendly(Rem 700's especially,as it is a 2.800"-ish box) due to it's shorter case length and is a hell of a cartridge in my opinion.

Re-15 screams in that case,with projectiles that interest me. While an 18.5" tube would not be my first choice,it makes much more sense than a lot of stuff floating around. If the chambering appeals to you,then why the hell not?

As for the 223Ackley,I have quite a few of 'em and the 20" barrel is my shortest(others are 22",23" and 24"). In my opinion that is an entirely adequate length and offers damn good performance from that slight package. I lean on 40's and 50's in all of mine and they absolutely scream downrange.

The 223AI is a MOST underrated cartridge,in my opinion...................

Here's a herd of 223AI's.............

Malm,

Sometimes I do the right thing for the wrong reasons. The only AI I ever built was a .257 AI for myself. I had a borrowed reamer and a short chambered barrel but no gauges, so I chambered for a slight crush fit on a factory case. Worked fine for me.

Since I am building for no one but me, if I ever get a flaming itch to rechamber something to another AI, I suspect that I will not bother to set the barrel back, but just treat the resulting chamber as a true wildcat. Forming cases from one size up is a lot easier than setting back a barrel.

Nevertheless, I am grateful for the information, Good to know how to do things right even if you aren't gonna do them that way. At least I now know not to do such a thing and fireform factory ammo.

Leftoverdj,

Sounds like you did the 257 AI correctly. If you are working with a short chamber as you were, then there is no need to set the barrel back. Just run the reamer in until you get a slight crush on a factory case...

To everyone else,

Speaking only of improved calibers that share the chamber of an existing factory cartridge i.e. 22-250AI, 243AI, 257AIs 25-06AI, 270AI, 280AI, 30-06AI etc, I offer this observation in general. There is an almost unstated, unwritten, unspoken obligation on the part of those who chamber such weapons, be it for themselves or for the public, to make sure that it is done correctly and safely. You're not always going to be around and the weapon may someday fall into the hands of someone with limited experience or knowledge who will insert a factory round and touch the trigger... If the chamber wasn't cut, headspaced or the barrel wasn't correctly stamped along the lines of the accepted practice of the day, then someone could be seriously injured.

Regards,

Malm