Thread: MV SD of wet tumbled brass vs inside dirty.

Hello Lads
Curious to know if anyone has any links to an experiment between shooting spotless cases vs internally sooty ones. I came across a rumour that just a fraction of a grain in case capacity will cause as much as a 20fts difference in MV (all other things being the same).

QuickLOAD predicts a 3ft/sec change in MV for a 0.1gr change in case capacity in a 6.5x47 case, a lesser change in larger cases. On the other hand I have measured at times up to a 25ft/sec reduction in MV from cases with cleaned inside neck surfaces from those where the necks have been lubed with graphite for seating, and usually somewhere between with cases where the neck was left with a residue coating from the previous firing. Certainly any experiment would need to hold the condition of the inside neck surfaces constant. From the QuickLOAD output it seems unlikely though. Burn rate being being influenced slightly?

I'd not thought of quickload! Cheers for checking that for me. Yep deffinately the effect of a .1gn change would be more pronounced in a smaller case, but im thinking a larger case may have much more variation than that. I recall looking inside my cases when using 2209 and the soot looked more uniform. 2213sc it looks patchy in there. Wondering if cleaned then that increases consistency between shots