Load testing with new brass

[Mikecr]

New & sized brass is not the same as fireformed & sized brass.
I say 40 extra shots here could save you more than 40.

[BML]

Im curious to know if anyone who has already developed a load has shot brand new brass and compared the results to that of fire formed brass.

What were the differences in groups, poi, velocity etc?

At this point I'm leaning towards loading as if I were testing.

[Lefty7mmstw]

I never much care in the rounds I use.
The 6.5x284 is a bit smaller, but it shouldn't make more than a few fps difference and unless your chamber is huge it should make little difference in accuracy.
I routinely use whatever brass I have for test loads, as long as it is all sized, trimmed, and at the same number of firings.
It's not like the case only expands to fill the chamber only after the first firing.

[MNbogboy]

It is almost certain you will see a difference in POI, velocity and most likely accuracy also.....But this information can all be applied as future reference as your load developement progresses....

As Mikecr implies the fireforming process is very essential to any load development....Personally I believe the cases are not fully stabilized till at least two firings....But most likely you may be able to "weed out" some obvious undesirable results during the fireforming process with the first 40 firings....Testing for seating depth is one for instance.....

My opinion is don't waste those first 40 shots just to "season" the case...Any info you record may come in handy later on down the road..

Randy

[Tumbleweed]

I discovered last year that there was a huge difference in my rifle between new brass and once fired, resized brass. This was NC brass. With the new, I chronographed the load at 3,040 fps. With the same load using once fired, FL resized brass velocity is 3,120fps. Accuracy, velocity and ES are all better with the once fired.

[BML]

Well I had plans to test 5 different loads today, but was interrupted by some much needed rain.

A couple weeks ago I tested a load on brass that had been fired 14 times. That 3 shot test shot an impressive .354. I knew I was getting close to the end of that brass life, but wanted to test a 12 shot group with that same load to get a good batch of data. The first 8 shots were all over the place. Then I split a case on the 9th shot so I called it quits.

Fast forward to today. First three shot group with brand new unfired brass, same load as the .354 group from a couple weeks ago, shot .451




I was able to test just one more load before the rain started. Same seating depth, but .010g less powder. This is brand new load so I don't have anything to compare it to. Shot a decent .555.



Now I know 3 shots represent a very small sample of how brand new brass performs against fire formed brass, but it's a start anyway.

[Lefty7mmstw]

I'm already at .3moa( 3-3shot groups separate days) with my 7stw with new rp brass using the 171 matchburner and rl25. An 8# 7stw shot off sand isn't going to get much better with fired brass.