Question on Fire Forming Improved cases.

[ve6ntt]

I've heard it said that you can fire form factory ammo into improved cases by firing them in an improved chamber! To me firing a 30-06 case with a 17 degeree shoulder in a 30 Gibbs or 30-06 Ackley which have a 40 degree shoulder that has been moved forward is the equivilant of excessive head space and dangerous!

I've also heard that some sort of reduced load must be used to fire form the improved cases.

What is the proper process?

Thanks

 

[Canuck223]

If the improved chamber holds the transition from the shoulder to case neck at the same spot, you should be able to fire factory ammo safely.

If the new chamber shortens the neck of the case, I would probably load the bullet long to engage the rifling, and use a very light charge to fireform.

 

[stocker]

Improved fire forming

Properly cut Ackley Improved chambers are about .004 shorter at the base of the shoulder/neck junction than the parent case. This is to impart a slight crush fit of the standard case in the improved chamber and guarantee head space is maintained. Rechambered barrels should be set back before re-cutting the chamber. You can feel the resistance when closing the bolt on a standard cartridge if it is done correctly. Not every so-called Ackley Improved chamber gets this little nicety done and the consequence can be stretched brass and prematutre case failure and a head space problem. This can be alleviated to some extent by pulling the bullets from factory laods and reseating them to a depth that provides bullet to lands contact to hold the cartridge back against the bolt face. It's not the best way to do it. Ackley had it right.

 

[tiriaq]

Theoretically, a factory cartridge should make contact with the neck/shoulder junction in an Ackley chamber, so first firing isn't a problem. If the shoulder is to be blown foreward, one way is to expand the neck, then size it back down until the case can just be chambered, with the small false shoulder making contact in the chamber. This is intended to hold the casehead against the boltface, and avoid a serious excess headspace situation for fireforming.

 

[ve6ntt]

Fire Forming Improved Cases

Ok

That makes sense for the Improved cases. I'm guessing then that cartridges like the 40 Gibbs, were the neck is appreciably shorter, must be formed with a custom die?

 

[Eagleye]

ve6ntt; I have a 30 Gibbs, and form my cases from 35 Whelen brass. When I run a 35 Whelen case through the Gibbs die, I end up with a shoulder right where it should be, and can feel the bolt close with a bit of resistance on the case. I then load and shoot it, and end up with a perfectly formed Gibbs Case. My 6.5x55 Ackley improved has the slightly "short" chamber, so when I chamber the standard 6.5X55 case, I feel a distinct resistance as I close the bolt. Fire the ammo, and remove the newly formed improved Case. A good smith will chamber the AI series this way. No fear of excess headspace at all. Regards, Eagleye.

 

[ve6ntt]

Fire Forming for Improved Cartridges

Thanks to all who replied; Just wanted to know! Maybe one day I'll need to own something that shoots improved?

Don