Velocity difference when changing brass

[EchoDeltaSierra]

I recently did a 6.5 Guys ladder (http://www.65guys.com/10-round-load-development-ladder-test/) on the GFs new Ruger American Rifle and thought, what the heck, I'll run a similar test on my R700. First off, it was super easy to find a velocity node for her rifle and the 10-round method worked really well.

With my R700, I've been using Nosler brass for my rifle's load and had a solid load already developed. I was curious so loaded a matching ladder with brass from some Hornady ELD Match ammo we previously fired (both rifles), shot the ladder, then reloaded 20 rounds at the chosen charge weight for some group tests. The results somewhat surprised me.

42.2gr of H4350 in the Hornady brass produced about 2650fps and shot well. ... but...
My existing load, 41.9gr of H4350 in Nosler brass produced 2690fps. Both measured with a Magnetospeed.

Is it typical to see that significant of a velocity change merely by using different brass? I suspect the Nosler is thicker, thus less volume, thus higher pressure, thus faster...but that is just a theory and it'd be interesting to hear some commentary.

Thanks!
-ES-

 

[Crang]

Yes. I have to rework loads when changing brass.

 

[supercorndogs]

Yes, its very common, just more talked about in .308. The 6.5 creed just only had one brass option for so long.

 

[LRShooter101]

YES!

Change brass, you change some dimension/thickness, internal capacity changes, and your resulting velocity changes.

If you use Quickload, you can make changes in the case capacity to account for this.

There are also plenty of references online that will show you case weights/capacities.

 

[Stpilot12]

Nosler, Prime, Norma Brass are almost identical (all made by Norma) and have less case capacity than Horny.. Lapua has slightly less than all those.
Always work up/tune for each case.

 

[918v]

YES!

Change brass, you change some dimension/thickness, internal capacity changes, and your resulting velocity changes.

If you use Quickload, you can make changes in the case capacity to account for this.

There are also plenty of references online that will show you case weights/capacities.

Which are often wrong.

The primary cause of error is they measure the capacity of a virgin case and QL needs the capacity of a case fired in your chamber. Second, it is unknown how they analyzed the water in the case. Did they have a concave, convex, or flat meniscus? The shape of the meniscus significantly affects the case volume reading.