Powder load: What's YOUR acceptable variance?

[indyjohn]

I ground a front sight blade down to about .010" high as well as removed my rear sight elevation rack and with a three cornered file I cut additional teeth for more adjustment.

Ha Ha, I've been there, my friend, I've been there. Lets just say the receiver on my M1A was ringing...

 

[Broom_jm]

I had the privilege of learning to reload at the foot of a former benchrest competitor with many trophies on his mantle. When I met him, he was in the late 70's and still shooting in the 5's or 6's, with boring regularity. His 6mmPPC was minute-of-postage stamp, all day long.

He taught me something about reloading that I'll never forget. His loads were not individually weighed down to a tenth of a grain. He worked with different powders, bullets and seating depths until he found a load that was both accurate AND tolerant of minor changes. Those 1/2" groups he was shooting were with loads of H4895, dropped straight from the tube. He took the time, one day, to weigh out a few loads to show me what I wouldn't have believed, otherwise. He intentionally loaded 3 rounds with .3 more powder than his base load, and 3 more rounds that were .3 less than his base load. He then took 3 rounds that were dropped straight from the tube, so he had no idea how close they were.

He took these 9 rounds, mixed them all up so there was no way he could possibly tell them apart. Then, he shot three, 3-shot groups. Every one of them was sub-moa, with nothing you could call a flier. In fact, 2 of the 3 groups were essentially one hole. That opened my eyes to just how unimportant being off a tenth or two can be...with the right powder.

I would not like to be off a full grain, but I do have to ask the question: If you're shooting these from a bench rest position, why would you not load them for the best possible accuracy? If you're shooting from off-hand or improvised rests, loads that vary as much as +/- .3gr will not keep you from enjoying the practice. The only real way to tell is to load them up "wrong" and see what the results are.

If you're going to use a progressive, don't choose a stick powder that doesn't meter well. That much is obvious. Also, if you want to crank out a volume of ammo in short order, don't nit pick about the accuracy you get. Progressives and MOA accuracy don't go hand n' hand. YMMV, n' all that.