Velocity jump with brass change

[Moe0001]

Hey! I've been reloading for almost a year now. 6.5CM and .223. I've tried loading with H4350 in the past with nothing special and eventually went with Superformance. I've finally upgraded my rifle to a Bergara BMP and began development again. I loaded up a few different powders and a couple bullets. One load was 42.5 g H4350 with 140g ELD-M. 5 rounds I got an average of 2817 fps, ES 6, SD 2. Load Development done! I then loaded a batch of 50 with some other Hornady brass - average now 2801 at a warmer temp. Not a huge deal, But then I loaded another batch with Starline brass and ended up way over pressure pushing 2875fps. I pulled a bullet and weighed the powder and it was right in line with what it should be. Has anyone seen such a huge swing in velocity from switching brass? Since I've picked up a couple hundred pieces of Hornady brass to keep all my loads consistent. I've never seen a wild swing like that loading Superformance. Does anyone know H4350 to be sensitive like that?

 

[lash]

What makes you think that the internal volume of the Hornady and the Starline brass are even close? Hint. They are not.

You cannot willy-nilly change major components without knowing the differences between them.

 

[Moe0001]

What makes you think that the internal volume of the Hornady and the Starline brass are even close? Hint. They are not.

You cannot willy-nilly change major components without knowing the differences between them.

That's why I've standardized to one lot of brass. I just thought that was a pretty substantial change. I predict that the fired brass will probably be a little slower than the new brass because of the increase in capacity. Actually, I fired a few load yesterday and I was getting pressure signs on the primer but no ejector marks. Using CCI200s. I'm wondering if maybe Magnum primers might help that or if I'm just not going to get the velocity I want out of H4350

 

[Kadams1563]

With any quality brass change you should drop a grain or two at the very minimum.

 

[MarinePMI]

IIRC, Starline brass has a smaller volume, which would cause a pressure spike using load data from a larger case (this is what I believe Lash was trying to tell you). Rework up your load for the new brass...

 

[Delicatessen]

As others have said volume either by brass or change from bullet depth from seating or by just a different bullet design will change your pressure quickly. I would try to standardize with good brass (Peterson makes reasonably prIced), pick a primer that is usually available, and then work up each combo of bullet and powder carefully be very careful if you are moving towards lowering the volume from a previous load by seating etc. if necessary you can always check case capacity with water with spent primer seated.

 

[Deleted member 10043]

Please don't experiment with compressed loads where others have before.