I just had a rifle built with a PacNor 250 Ackley Improved barrel. I've fire formed about twenty rounds of Rem-UMC 250 Savage ammunition with no real issues and I've reloaded them using RCBS dies and all seems well. I also acquired about 20 loaded rounds and 5 fired 250 AI cases made from Nosler 22-250 brass. These are causing me some trouble, however.
Neither the Nosler reloads nor the fired cases will chamber in my rifle. The bolt will not close on the round. I tried resizing one of the fired Nosler cases with the RCBS 250 AI dies and the bolt will still not close on the resized case. I was hoping that I could use 22-250 brass to reload to 250 AI but now I'm not sure I can.
Any idea of what is the matter?
Personally I would rather do it with good quality .243 Winchester brass. I do the 6mm/250AI, and case shrinkage would be excessive with 22-250 brass because your moving a lot of metal around. The shoulder on a standard 22-250 is about .414", while the .243 is .454". I saw .035" shrinkage, but with the .243 case it was about half that. I know it's a little more work, but the results prove themselves out.
Lastly, and before you ever do a single case. Find out the exact length of the chamber neck length. Trim your case about .008"-.010" shorter than that number. The neck length will often be .025" or longer, and this will only help your situation. The brass flow on fire forming will move the neck back towards the case rim, so don't worry. My trim length comes in at 1.933", and anything added into the length helps throat life (although not much here).
Your going to really like this round by the way! It's often regarded as Parker's best design (I'm also a big fan of the 6.5x57 and 7x57 rounds he did as well). Be nice to see somebody do a new series of 25 caliber bullets with a high B/C.
gary
P.S.
I must apologize for not addressing your issue.
The rounds will not chamber after being resized? This as others have said might come from a minimum spec'd headspace. (we're never that lucky!). This is going to be hard without some tools to make measurements with, honestly. If you have a couple cases that have not been thru the die, leave them alone and keep them separate.
I would make a trip over to Harbor Freight, and buy a 6" digital caliper. Buy a steel one, and stay away from the cheap stuff. Next I would get the phone book out and find a ball bearing outlet (not Tractor Supply), and buy something like a .500" ball bearing (they are not expensive. A 12mm would be even better! You'll use the ball bearing as a gauge to check your caliper. Down the road buy a one inch micrometer, and learn to use it accurately. Don't buy a cheap Chinese micrometer, and you want generic steel anvils instead of carbide (you get a better feel).
Now it's entirely possible that you have a die cut towards the max length and a chamber cut to the minimum. I would take a case you've sized, and run it thru the die again. With the case all the way in the die (max stroke), I would see if the die was contacting the case holder (assuming your using a typical O frame press). I don't think your press is flexing doing what you are doing. I do some serious wildcats, and I have been known to remove as much as .015" from the bottom of the die. But I've known guys that were able to remove .010" from the top of the shell holder. This not a common thing to do, and I really doubt you need to do this. Plus I think we're really looking for .003"/.006" headspace relief here.
I wish you were near me, as I'd bring the measuring tools and we'd get it done.
gary