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Discussion Starter #1
It warmed up enough today to try out the .243 I picked up at the gun show last month. Loaded up some ammo and cleared a trail to the range. Had to pack the snow down on snow shoes and put up a new target backer. First round went click. Second round also went click. Back to the shop where I took the bolt apart and checked the firing pin and spring. Couldn't find anything wrong so I made a visit to my local gunsmith. We poured a cast of the chamber and found that it wasn't chambered for .243 Winchester after all. We think It's chambered for 6MM Remington Ackley improved. Now I need to get new dies and brass. While I was there he checked the barrel and chamber and said that it hadn't been fired much and there was no wear in the barrel or throat.



 

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Wow... I wonder if the guy made a mistake or forgot to say it was the AI chambering? If I had something like that happen at teh range, I would be puzzled to say the least!

Are you able to tell for sure what chamber it's in from the cast?
 

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Mate, thats too bad. How hard is it going to be run 6mm Rem AI??
 

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Discussion Starter #4
Well, as it turns out the gunsmith was wrong. Who'd a thunk it? Got to playing around last night and made up some 6 MM Remington brass from some 7X57 brass I had and found that they wouldn't chamber. Way too long. Laying in bed last night I had solution pop into my brain just as I was going to sleep.

This morning I got out my 6.5X55 dies and ran the expander into the neck of 5 cases. The I ran those cases almost all the way into a .243 die which left a false shoulder on the neck, preventing the case from going all the way into the chamber. I loaded those cases with 10 grains of Unique then filled the rest of the case with Cream of Wheat and topped it off with a polyester filler. Fired the case and found a perfect .243 AI case with a few thousands extra head space. Now I just need to make 500 more cases.

Left to right: Standard .243, 243 with false neck and polyester filler, .243 Ackley Improved.


The .243 AI is a great cartridge. http://www.6mmbr.com/243win.html
 

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Ohhh nice. Thats good. Hope it works well mate.
 

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I'm confused as to why the standard .243 didn't fire in the .243AI rifle. Even P.O. Ackley recommended fire forming using factory .243 rounds because you needed the pressure to properly form the case. I know there are other methods to fire form that work just as well. Let us know how it goes when you get back to the range. Great looking Rifle!!!!!!
 

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Discussion Starter #7
a300fe1 said:
I'm confused as to why the standard .243 didn't fire in the .243AI rifle. Even P.O. Ackley recommended fire forming using factory .243 rounds because you needed the pressure to properly form the case. I know there are other methods to fire form that work just as well. Let us know how it goes when you get back to the range. Great looking Rifle!!!!!!
Me to. I think that when the smith chambered it he went in just a bit too far with the reamer. It's a comon problem with AI rounds. I had a .223 AI that had the same problem. It only takes a little bit to allow the case to move forward enough that the firing pin will push the case forward and not fire. There was a nice indentation from the firing pin so we're only talking about .002 or so. In short, the whole purpose of the Ackley mod is to be able to use factory cases and gain some speed. In my case, I would want to shoot higher BC, heavy bullets at a velocity that will keep me supersonic at 1000 yards. With this round I'll be able to shoot along side the 6.5-284 using less powder, less recoil and less cost.
 

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That's cool! I've heard of the fireforming cases... but have never really seen the "before and after"! Will you have to fire form each case like that or can you just get some AI cases?
 

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Discussion Starter #9
No, they don't make AI cases. After I put a false shoulder in the rest of them I'll just load them as I would a normal 243 and plink with them. I've got a bunch of 6MM bullets that I tried in other guns and they didn't work out for some reason. The cases I already did with the cream of wheat were because I really didn't know what I had. Now that I know the measurements of the chamber, I can get to work.
 

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Discussion Starter #11
SemperFi said:
How long will an AI case last after you fire form it like that?

Interesting process to say the least!
I'm not really sure since I'm still new at this. For one thing, they don't stretch as much with the sharper shoulder so that should help. Neck cracks have always been a problem with my other .243's.

It's turning out to be a beautiful, but cold day here so I'm heading out to the range.
 
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