black soot on brass

[britz]

I was messing around testing some loads in my 300wsm. 64g vargete, 110g vmax and BR2 primers. I have shot them before and it seems to be a fairly moderate load. I decided to test seating close to the lands to see if it would affect accuracy much. I was only able to seat them 0.008" from the lands and that was absolutely it. The bullet was seated by about .02 or so into the case. I fired the first shot and immediatly could smell a strange odor from my rifle. Easy ejection and noticed that the case was sooty. SHot the next two with the same affect. Impacts were ok - 1.5" at 200 and the primers were not flat at all.

I was thinking that because the bullet was almost setting on the case that the chamber pressure wasn't able to make an immediate seal around the case causing some gas to leak out around the case and bolt before the case was pushed tight to the walls. Does this make sense? I dicided to abort the rest of my test shots with seating them so far out.
Thanks for your input, Mark.

[Fiftydriver]

Generally, this is cause by very low pressure. This could be caused by the very light bullet with very little neck tension on it preventing a good powder ignition.

Generally, going to a hotter primer will help and generally increased the powder to jump up pressure will help also.

As the cases are fired more and more, the case begins to heat temper as well which means it looses its elastic properties which allows it to expand to seal the chamber as easily as with a newer case. This can be corrected by annealing your case necks and shoulders.

Simply put, if you have no other pressure signs, I would say working up your load will make this problem go away to some degree. That said, very light bullets in this class of chambering can results in these issues no matter what but you should be able to limit this to some degree.

Kirby Allen(50)