[rick w.]

A while ago, I got hold of a 17 MachIV Cooper 21 varminter. Pretty nice condition but new guy to Cooper's. Came with form dies and reloading dies but no brass.

Formed some brass from 222 remington, but going to have to neck turn. I have read a time or two, that Cooper had a tighter chamber, neck was 201.5?.....

I need to assess a scratch left on the brass, a scratch along the boreline, from the shoulder about 1/4 inch down in length. Not sure if that is the chamber champher or perhaps the strong ejector pushing into something along the ejection routine.

The 17 MachIV is an old wildcat, was curious what folks' factory Cooper rifles were measuring in the neck area? Maybe in the old days was a no turn 221, but just guessing here. I passed up 1000+ 221 Remington brass earlier this year...............go figure huh? Have my 222 brass formed to MachIV now except the neck turn, so almost ready to go.

I suspect that I will pull the barrel to try to figure out the scratch thing, and can access the neck more easily on this rifle.

Just courious about other Cooper MachIV's(mine is a 21) in the neck area....