7mm Remington ultra mag brass to 300 Remington ultra mag brass

[morbidking]

Anyone ever try to fireform 7mm ultra mag brass to 300 Remington ultra mag brass have access to a lot of 7mm ultra mag brass but don't have a 7mm I have the 300 ultra mag I thinking it should be doable

[tygar]

Put 10gr of Unique in it, plug with wax or whatever & pop one off. Should fit like a glove.