Fire forming Lapua 243 to 22 CHeetah

[MEHavey]

> The first case came out easily, the second was a problem.
> Tapping the bolt handle to remove the case with a rubber
> mallet is not my idea of something going right. Seems the
> Lapua brass is a bit larger in the web area, and even though
> I resized it in a 243 FL die, this brass is not going to work
> for the CHeetah.

I'm surprised. Would the unfired cartridge chamber and then extract (unfired) without problem? If the cartridge could do that w/o sticking, the very thickness of the web should never cause a problem in that area unless unusually high pressures are involved (i.e, the kind that causes head expansion.)

NOTE: QL shows that 41gr/4895 under a 55gr bullet in a Cheetah MkI to produce ~57,000psi ... 7,000psi over max for the cartridge (as listed), and that's for "normal" brass volumes. Three things may be happening:

- You have a high pressure load to start with
- If I drop the "normal" case volume by 3% to account for Lapua thickness, QL pressure jumps to 60,000psi; Drop it by 5% and it hits 66,000(+)psi
- Did you turn the necks in case the .243 -> .224 resizing might induce neck constriction?

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Matt Anthony]

Yes, that load was very hot, too hot! The data I received from the previous owner was totally incorrect and extremely dangerous. Now I understand why he gave up!
I'm starting over, fire forming without bullets using green dot.
Using the Lapua 243 brass, the procedure to reform for fire forming is rather simple. There is no neck turning required.
First, I full length size then use the Jones forming die with the .250 neck diameter bushing, forming the neck and bumping the shoulder near the neck down .050. The shoulder now is not straight, it's convex to the naked eye. I then use the Sinclair neck turning mandrel and run the neck through it which straightens out the neck. I then trim to 2.012. I check to make sure it chambers and it's ready for fireforming.
As far as the QL data, I checked it and was astounded! Never, never trust anyone's loading data, NEVER!
I'm 60 and still learning, boy that sure was a lesson learned!