velocity loss throughout case life.

[ajhardle]

I understand velocity loss will happen after fire forming, but I didn't expect to lose so much more. I stared with an accurate load of 23.2 gr of 844 to reach 2930 fps (my accurate node happens to be Berger's published max for the 70VLDload) . This is from once fired, not new. Now for the fifth firing, I'm up to 23.8gr to match velocity. Now, I've done no sizing other than lee collet neck sizing because the lapua brass has a neck so thick I will need a bushing die (top of my list of things to buy).

So, question is-it's what I'm recording normal, and how much a difference will f-l sizing make?

 

[Mikecr]

By the 3rd firing your MV should have stabilized, as the cases should have reached pretty much fully formed. This is not a problem.
That you load developed before cases were stable, that's where you left yourself.

 

[boomtube]

Is that drop in velocity coming from the same container of powder?

 

[ajhardle]

Same container. I even have my scale fixed to the bench. I check zero quite frequently, but it's been so long, I can't recall when it was last off.

Mike, thanks fire the info. I think I might go to the range and reload once until it splits just to see how velocity changes with each firing. Maybe try it again and see if I can keep it in the node.