Just posted this over on UKV and pigeonwatch but thought I'd add it here to open it up to discussion on old powder.
Having picked up my .20Prac Sako A1 from Neil Mckillop a couple of summers ago I've been reloading using an old tub of Viht N133....... I'm sure I've read that powder goes off but you can tell that by the smell losing that ammonia type edge...... the tub still has that whiff.
There's nothing untoward in the performance and I get good grouping at 24grns at an average of 3671fps which is pretty much on a par, or even slightly less of a charge, with what other .20Prac owners load to.
But I do get staining/acid etching of the next bullet head loaded into the chamber after firing a shot......... the smell of the fired shot is sulphurous.
The round on the right was chambered for 2 hours after 10 shots zeroing 2 'scopes to the rifle. (On a side note I'm really impressed with the new Photon XT 6.5!) The barrel was cool between shots walking to and from the target each time.
Shot 4 foxes with the rifle last night within a half hour slot and the middle bullet is the one chambered after that for another 3/4 of an hour.
The fired cases all extracted as you'd expect without signs of undue pressure...... I'd have thought the presence of fluid around the bullet must be increasing the pressure too!
Is my powder past it's best?