Seeing those results on a chronograph, and nothing "happens"( no outward signs of pressure) is what we get when a bunch of amateurs (us) gets turned loose with a bunch of powders full of promise and a chronograph, with a million variations in components and barrels,and some pet cartridge.
If you do this stuff often enough eventually we run into these velocity anomalies,there are no outward signs of pressure we can detect with our "guessing" techniques and we think everything is fine and some miracle powder gives these results.
Just as examples,similar situations I've walked away from include: 3200 fps from a 22" barrel 270 and a new lot of RL22; 3100 fps from a 150 gr in a 23" 30/06 barrel and H205;3300+fps from a 160 AB in a 7mm Mashburn and a load of Retumbo;one 7 Rem mag that gave close to 175 fps more velocity in one rifle than another with the same load of H4831.
There have been others but the point is that familiarity with the cartridges and lots of data told me those velocities were over the top,even though there were no outward signs of pressures to indicate I was over the top.Those are the kind of loads that will sneak up on you one day,or leave you in Montana on a hunt with a seized up action or worse. Bad practice.
Dunno know about anyone else but when I try to figure what a cartridge will do I don't look at the max velocity in a manual or what one person got without getting into trouble....too many variables and you have to leave yourself some wiggle room. Just because we see these velocities,even with manual loads,does not mean they are safe in our rifles.
It means we are redlined and a small step or slight variation away from bad stuff.
