Thread: Fire forming 270 to 280ai

An alternative method is to use a shotgun powder to fire form the cases, so you won't be wasting bullets. When I fireform 303 cases into 7x57R, I anneal the neck and shoulder, then open the neck of the case to 30 cal and then neck it down gradually in the 7x57 full length die until I find a firm fit of the case into the chamber with the action closed. This gives me a group of cases which have a tight headspace in the rifle chamber. Then load the shotgun powder (I used Green Dot) into the cases as a series of cases with load increments. A square of toilet paper in the neck holds the powder in the case. I fired the cases from the lowest charge up until I found the correct level of charge that formed the case enough. 18gr gave a fully formed case body with slightly rounded shoulder corners. 19gr did not make the shoulder sharper. That comes with shooting the cases with a bullet.

Originally Posted by rupert

An alternative method is to use a shotgun powder to fire form the cases, so you won't be wasting bullets. When I fireform 303 cases into 7x57R, I anneal the neck and shoulder, then open the neck of the case to 30 cal and then neck it down gradually in the 7x57 full length die until I find a firm fit of the case into the chamber with the action closed. This gives me a group of cases which have a tight headspace in the rifle chamber. Then load the shotgun powder (I used Green Dot) into the cases as a series of cases with load increments. A square of toilet paper in the neck holds the powder in the case. I fired the cases from the lowest charge up until I found the correct level of charge that formed the case enough. 18gr gave a fully formed case body with slightly rounded shoulder corners. 19gr did not make the shoulder sharper. That comes with shooting the cases with a bullet.

That method was recommended to me by Robbie Tiffen for blowing out 223 cases to 6mm.
But no gradual sizing. Just fill them up with fast powder and bang, it's done.
Obviously trimming to length was required.