Long(er) necked version of 7 WSM

[davidjoe]

Guys, on the question of what a 300 WSM necked down and shot through the Mega looks like, it’s this.

I’m not very experienced with fire-forming but to my thinking, the 200 line appears to have stretched. The neck shortened.

As a general proposition, where is the line between what is viable via fire-forming, and what is not?

 

[rpierce]

Guys, on the question of what a 300 WSM necked down and shot through the Mega looks like, it’s this.

I’m not very experienced with fire-forming but to my thinking, the 200 line appears to have stretched. The neck shortened.

As a general proposition, where is the line between what is viable via fire-forming, and what is not?

if you form mega brass from wsm brass the neck will end up .050 shorter than the chamber. youll wanna just buy the mega brass from shermans website. if a guy doesn't hot rod it the brass will last a very long time. I have 15 firings on a piece of 7 mega brass and the pockets feel almost brand new.

 

[davidjoe]

if you form mega brass from wsm brass the neck will end up .050 shorter than the chamber. youll wanna just buy the mega brass from shermans website. if a guy doesn't hot rod it the brass will last a very long time. I have 15 firings on a piece of 7 mega brass and the pockets feel almost brand new.

It really is significant. I took a new picture that compares Sherman stamped brass, fired, to the fire formed Lapua piece.

This photo aligns the top of the necks, to emphasize the difference.

I’m assuming the Lapua case’s brass would likely continue to “migrate” toward the neck, potentially thinning the area where incipient head separation can occur around the 200 line.