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"Bad Joke Friday" Dan (moderator emeritus)
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Copper,

Very good question. The primary two results I look at are the Std. Dev. which will give you your distribution as has been already nicely covered. The second criteria is the ES or Extreme Spread, which is nothing more than subtracting the slowest velocity from the highest velocity to determine the ES. As you can certainly guess, the smaller the ES, the better. But I no sooner say that then I refer to dodgestdshift's comment "Note this may not be the most accurate load."  I can't explain the magic (or whatever it is), but your smallest SD/ES may not be your most accurate load, but they are typically very close to being the best load and certainly are excellent indicators.

I would suggest one more function of your timing device that can be critical, and that is in determining your max. load. If, as is common, you start a few grains below the reference book's maximum load and work up, your velocity increases will be linear (not perfect, but fairly linear) to a point at which your velocity increases will significantly reduce or disappear. At that point, more powder will only dynamically increase pressure without velocity increases and you've obviously reached a maximum powder point. As I'm sure you've noticed, the reference books vary, and using the chrony to validate your particular rifle and components "point of diminishing returns" is a profitable use.

For a much better explanation on this important function, I'd sure suggest that one of your best buys would be the Beartooth Tech Manual.

Dan
 

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"Bad Joke Friday" Dan (moderator emeritus)
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7,761 Posts
Jack,

A "real statistician" would sure be disappointed with my efforts! I plan on knowing all I want to know about a particular load way before I get to the 33rd shot! But your point is well taken as I have noticed when I shoot/calculate five 5-shot groups individually, and then calculate the aggregate, the five groups vary from the aggregate somewhat.

Copper,

I'm afraid I'm not able to offer any additional suggestions on your techique, but I will tell you that my tests indicate that however hard I try, there is some inconsistency. By that I mean, I'll load and test one day, load with what I consider exactly the same load the next day, same settings, temperature, etc. and and the two day's results will vary. I'm not talking about accuracy, but the performance data we've been discussing! So as far as I'm concerned, you're on the correct path to think along the lines of good loading technique, because consistency isn't a given.

Dan



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"Bad Joke Friday" Dan (moderator emeritus)
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7,761 Posts
Copper,

Apologize for not paying more attention. MikeG's excellent recommendations alerted me that the questions pertain to rifle, not pistol, cartridges.

My remarks are directed to someone interested in increased accuracy (sub-MOA) for target purposes, not sporting rifles looking for 1.5" at 100yds.

1. Completely agree with MikeG's recommendation for gauges for determining the overall length for best accuracy. I use the Stony Point mechanism to determine bullet seating depth to result in the bullet olive being .003 off the lands. That improved my accuracy for my .223 in 14" Contender.
2. I also do something that is a time consuming pain in the neck, but it also made a noticable accuracy improvement, and that is I trim the necks to assure they have equal thickness.
3. As Jack and Mike point out, gauges to check concentricity and run-out also help. When I got started, I read everything I could get my hands on and then bought "a bunch" of equipment. Then I came accross an article that said that the primers, bullets and powder have pretty good consistency, but that 90% of the problem(s) was with the brass. The article concluded with the advice that you should consider buying the best brass in the first place, and every since then I've purchased either Lapua or Norma brass. In every instance, the concentricity, run-out and weight have all been within the benchrest recommended criteria. The better brass is expensive, about $54 a hundred versus the usual $15 a hundred, but it sure took between .5" and .75" off my 100yd. results without any additional efforts. And if reasonable loads are used, eight to ten reloads or more are common.

Dan
 
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