243 necked up to 250 ackley... problem!

[gil_wy]

I bought some 243 cases to neck up to 250 Ackley (recommend by several people as a good conversion that doesn't require fire-forming) and I keep crushing the case right below the shoulder... What am I doing wrong? Doesn't seem like a big leap... shoot, I've necked down 270 to 22-250 just to see if I could... Is the flat shoulder the problem? Maybe I'd have better success going down from 260 brass? Any suggestions would be appreciated...

 

[NCsmitty]

Are the 243 cases new or have they been fired? Are the cases crushing with the expander, or when you try to move the shoulder back?



NCsmitty

 

[Sunray]

You're playing with the wrong case. The .250 Ackley is just an improved .250 Savage(aka .250-3000). Difference is only the shoulder angle. 26 degrees 30 minutes for the Savage. The Ackley's is 40 degrees. You'll have to fire form.
The .243 has a 20 degree shoulder and is 133 thou longer. That 133 thou is likely why you're crushing the case.
Midway wants $29.99 per 50 for Winchester .250 Savage brass. $266.99 per 500.
The .22-250 is a necked down .250 Savage as well. Not a .270.
The .260 Rem has a 6 thou smaller rim diameter and is 133 thou shorter than the .250. Give you issues the other way, lengthwise, and likely extraction issues.
Cartridge dimension drawings are here. http://stevespages.com/page8d.htm