Thread: 6.5 Creedmoor load development

Originally Posted by Puffin

I found Lapua brass in 6.5x47 seemed to stretch more on first firing with a moderate load than expected, giving the impression of high pressure on extraction. This may have been behind your AR2209 experience? Perhaps your brass is similar in composition and manufacturing process (as the cases are in design) and prone to the the same behaviour? For a given load it affected some cases more than others in a way that could have been interpreted as "spiking". QuickLoad couldn't match the velocity and powder charge to the pressure signs by a large margin so I knew something odd was up. It settled down on a repeat firing, and then I lightly annealed and that fixed it completely.

A very likely theory, I didnt measure the virgin brass before the first firing and compare it to resized dimensions but that is very likely. However I fired about half that virgin brass with 2208 and hotter loads than the milder 41gr 2209 loads without any sticky bolt at all.. I would have thought the 2208 would have produced higher pressures than the 2209. This Is why I first suspected the full case was lifting pressure beyond what it should be as the 2208 had a lot of empty space under the projectile.
I should try a few more 2209 loads with the same original deep seated COAL at some stage to try and replicate the initial results.