Well here is the deal. I looked on Nosler.com and they show that you can put in more powder than what this reloading book shows. I think the book is either outdated or being pretty conservative. Plus I believe it's an older book.
We did not chronograph test loads. I'm going strictly to what the ammo box says and what the book says. And as some have mentioned, they may have fudged their numbers a bit or shot under ideal conditions.
most rifles will shoot best just under max pressure. pressure being the amount of powder you can safely put into a case. if you have questions in regards to where your at look at your primer after the shot and the casing around the primer. if you see little black specks, that's gas leaking out the primer and your likely at max and if you go anymore you will risk blowing the primer out the back. i.e. not safe.
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I do agree a chrono is the best way to do it. you could do a "drop chart" say for 4-5 different velocities. shoot at 100, 200, 300, 400, 500, etc and you will likely start to follow a a curve and could make a pretty good guess at what velocity your shooting at in comparison to the drop charts you created.
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what I do is start on the low end and work up. shooting 3 shot groupings. My 7mm got more accurate as I went up with powder but noticed I was at max pressure and dropped .5 gr powder no pressure sign observed and just slightly looser group then the max pressure.