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Discussion Starter #1
What kind of increase in velocities can I expect if I simply rechamber to the AI using 80-85gr bullets?
 

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Here's what my 6MM AI did

A while back I had a Jim Borden built 6MM AI and I shot 80 grain Bergers
in it and the velocity was around 3,800 fps. Really accurate and was a
real bomb when the bullet arrived. Sold the rifle, and wouldn't mind having
another one.
 

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Discussion Starter #4
wow, with that bullet and that velocity you could really reach out there couldn't you?
 

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243ai

I have a 243AI 10 twist sending a 70 grain blitzking down the pipe at 3850.
This is a flat shooting table rig and I'm sure the 6mmAI will do it better. I was looking for a cartridge that was flat shooting to help me get into the 500 yard club, and the 243AI has done it for me. I would try either one. Sounds like Don is sending the 80 grnrs down the tube at what I'm doing with the 70's. I bet that is a BOMB when the bullet connects!:eek: Sam
 

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Per Ackley

My 6mm Remington Varminter is zinging the Winchester 75gr HPBT at 3750'ps thru the screens. I am loading 47.5grs IMR4350 in Remington cases. Shot this load for the last 20 years and nothing has changed. I looked in my Ackley books for any helpful info for you.
Per Ackley concerning the 6mm Ackley:
"Since the standard factory cartridge is about maximum capacity for the 6mm bore, only a modest increase in velocity is possible by any so-called improvement and this increase is only possible by the use of considerably more powder".
For the 243 Ackley, his comments are:"The Ackley "improved" 243 Winchester is quite similar to the Mashburn version with little or no preference between the two. The Ackley version was created by popular demand, not with the idea of greatly improving on the original 243 Winchester which itself might be termed an "improved" cartridge".

Ackley, while a master in his own right, was very conscience about folks wanting more speed/HP, most often regardless of cost. As we know reading his commentaries, once you pass the bore capacity with case capacity, barrel life is shortened. To what extent that is acceptable is only a question you can answer. While a lot of his "improved" cartridges are really neat, like the 257 Robts Ackley, not all of them wore his seal of approval. Some he called just plain dumb. The cartridge 22 Earsplittinloudandboomer comes to mind but it does not wear his name, but does demonstrate how crazy you can get. I find none of his commentaries or writings to support that there is much to be had from his "improvenment" in this caliber. Differences in barrels will attribute to more to speed than his cartridge for this caliber.
My .02 and your mileage may vary
 

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Discussion Starter #8
Can anyone explain this statement to me?:
...once you pass the bore capacity with case capacity, barrel life is shortened...

In this context case capacity is obvious... how much powder the case can physically hold and still make a safe loaded cartridge. But what exact is bore capacity?
 

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I'll try.............

.... but there are many more learned folks that may comment further.

My concept of 'bore' capacity, or the 'over-bore' condition, is when a case is enlarged to hold bigger powder charges, and the velocities gained from the extra powder do not reflect the powder increases. i.e.: In an ideal situation, you should see significant velocity increases (relative, and subject to personal interpretation) for powder increases. When the velocities don't increase much, or at all, you have reached the 'over-bore' condition. This is assuming you stay within 'safe' pressure limits.

At that point, you are burning excess powder for the bullet, barrel length, etc, and providing undue heat and erosion in the throat, contributing to needless barrel wear.

Someone please add to my knowledge.
-West
 

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There's not much difference in performance with the standard .243/6mm cartridges. But look at both cases....the .243AI doesn't blow out a whole lot and performance still increases enough to make it worthwhile. But the 6mm case has more than twice as much body taper and Ackley-izing blows it out a whole lot. Now you've got a very substantial increase. One friend shoots 70gr bullets at 4150 through a long barrel, and that combo is very flat shooting. It's a whole 'nuther ballgame.
 

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Discussion Starter #11
4150??:eek:
What kind of barrel life does he get shooting that???
 

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4150??:eek:
What kind of barrel life does he get shooting that???
I really don't know, and I don't know if that's a working (accuracy) load either. But like any other cartridge, barrel life can vary according to shooting and cleaning habits. I'll get him on here to answer your question.
 
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