Fireforming 260AI

[Rock Knocker]

I know this has been beaten to death but i just want to make sure i do i right.

Im useing necked down Winchester 7-08 brass and the bullet touches the grooves at an OAL of 2.783. Should i seat the bullet a hair longer than that or just less then touching?

Also I have some R19 and some Varget, i planned on using the R19 but Varget is also an option. How much of one or the other powder should i use?

Thanks for any help, this will be a first for me.

 

[CaptainMal]

Doubt seating depth would matter. AI's already contact the old shoulder angle so the case should not be moving forward.

Don't have a 260AI but do have a 22-250 AI. Formed all cases without touching with no issues.

 

[fguffey]

Rock Knocker, depends on how the chamber was cut, the neck on the Ackley Improved case is longer than the neck than the parent case neck. If the ackley chamber is cut using an existing chamber all of the old chamber is not removed.
If the Ackley chamber is cut using a short chambered barrel factory, minimum length/full length length sized ammo can be used, When fire forming minimum length ammo in a new Ackley chamber the neck is sized when chambered (head spaces), the case then forms the rest of the shoulder and case body when fired, remember, measure before and after, when forming/fire forming case length will shorten .035 thousands when fire forming 30 Gibbs, meaning the case shortened in length as the case increased in diameter. Forming 35 Whelen and 338/06 from 30/06 will shorten as much as .040 thousands, and no the neck does not get thicker and or thinner, the neck gets longer or shorter when necking up or down.

F. Guffey

 

[bsekf]

I would just run the 7-08 case into a 260 die until the bolt will just close. Make a false shoulder, then it won't matter where the bullet is seated.

I have had trouble using the AI die when necking down. I seem to crush some cases.