New brass vs old brass - same load data

[ngnrd]

Will performance (velocity, POI, accuracy, etc...) change if load testing is done with new brass, and then that data is used to reload that same brass (now once-fired)?

And if so, will there just need to be a little tweaking, or will the load load testing have to basically start over?

Or, conversely, if there is a load that is known to work well in used brass, can that load be used in the first firing of new brass of the same headstamp?

 

[rcmodel]

Well, I sure hope so!

I for one can't use new brass all the time to duplicate the load I developed in new brass.
Then develop another load in used brass so I can load the new brass different after I shoot it once!!

Brass is brass.
I shoot new brass until I have enough used brass, trim it, and then go for it from then on with the same load.

rc

 

[243winxb]

If you use the exact same load, with matching lot numbers of bullets, primers and powder, there will be little change if full length resizing. This is using Rem. & Win. brass. Loading factory brass without sizing in 243win will group about 1/4" larger than fired brass reloaded using bushing dies. Conversely, when using standard FL dies with expander, i have seen groups enlarge as the neck wall thickness thinned from over working the brass. This is not common. Groups are never over 1" @ 100 yds.

 

[ngnrd]

So, everything should be good then. I was wondering because I know that brass forms to the chamber when fired. For instance, my brother's empties are tighter than mine when chambered in my rifle. In fact, they're tight enough that I wouldn't use his brass in my rifle without full-length resizing, but I can just neck size mine. I just didn't know if that slight dimensional change from new to "fireformed" would make any difference in performance.