New brass versus used brass chronograph difference

[ivankonev]

I was chonographing a new load yesterday, and had some cases that had been <span style="text-decoration: underline">reloaded several times</span>, and some <span style="text-decoration: underline">new</span> cases.

The new cases were 50-60 fps <span style="text-decoration: underline">slower</span>. The powder charge, bullet, primer was the same for both, the only difference being some of the cases were new and unfired.

The difference was enough to affect my zero setting on my scope.

The big question being: if <span style="text-decoration: underline">one</span> case in a batch you've been reloading starts to looks questionable (neck cracks etc), would you have to throw out the <span style="text-decoration: underline">whole batch </span>and start with ALL new cases to maintain consistency?

 

[Stevos758]

Re: New brass versus used brass chronograph difference

I am fairly new to reloading and I believe you should not mix cases like that. I have my batches and keep them all together. I would guess that the new cases have not been fire formed yet? Are you full length sizing or neck sizing only? Has any case prep been done to the fired ones that has not been done to the un-fired cases? Primer pocket uniforming/flash hole uniforming etc? How many firings on the cases? It's possible the brass is becoming hardened resulting in a difference in neck tension. There are a lot of factors that come into play. Hopefully someone with more experience will chime in.

 

[Michael Courtney]

Re: New brass versus used brass chronograph difference

I keep new brass separate and keep each group segregated by the number of firings until necks start to split. After some necks start to split I put the brass in the "practice only" group which really means practice from sitting, kneeling, or standing positions and I reserve prone and bench work for newer brass with a careful count of firings and careful case prep.