Variance between manuals

[golfballshootr]

Apologies gents if this has been asked before, but here goes.

The question is; why is there such a varied range between starting and max loads for the same powders? Hornady, versus Speer, versus Nosler, (also powder manufacturer websites)? I have wondered this before but, it came up last night with a friend getting into loading. I don't know the correct answer, I just told him that I always erred on the lower side and worked up.

 

[Brian Pfleuger]

There's variance in the published data because there's variance in the test equipment and conditions.

Think of it this way... why do we "start low and work up"? Because all guns, all powder lots, all primers, all cases, all scales and dippers are not the same.

The published data is really no different. Some of them don't even use test equipment, they do no more than you or I could do (guess), other use test equipment on standard guns, others use test equipment on universal receivers. Besides that, one might use Remington primers and Remington Cases, another CCI primers and Federal cases, a third Federal cases and Remington primers....


So, short version, there's variance because there's variance.

 

[RC20]

I get to jump in on this one (note while I was making a wonderful missive Brain jumped in line and beat me to it, his version is better! - forgot to mention the primers but cases also play a part)

I don't mind the question, good one though you can Google it you don't get the active discussion. Enough views (opinions) and you an form your own idea of what valid.

Probably the first one (my opinion) is how conservative the maker of the manual is. Falls into two groups, those who make bullets and those who make powder. Mine are bullet maker manuals, no powder though I do ref the power companies on line.

Just an aside my go to manuals are Sierra and Hornady as they provide a wide range of bullets as well as a wider range of powder listings than others. Even if you don't use their bullets they almost certainly have a weight and close profile of everyone else's.

Both list Rifle, twist and barrel length tested with.


The other has to do with what rifle (or test setup) they do their testing in. That also changes things a lot.

In older manuals the load levels were hotter, but also keep in mind powder has changed some as well so stay with current manuals.

I look at all my sources and select usually a mid range load to start with, but that's me, I just bench shoot and am not after hot loads.

You should be safe is you stay conservatively inside the limits of the two widest listings

Pressure signs are an elusive thing and the best check is a chronograph to see if you get a sudden increase in velocity if you are in the upper end.

All guns are different so the results are going to be different.

Powder lots vary as well. You would need to know the person who does the test protocol in each organization to really understand what drives them, you can only get a general outsider idea of the variances involved (and probably people bias in each organization as well not to mention legal)

 

[Clark]

I had to fly to Atlanta [with contract managers as their technical armament] in 1988 because Marconi had received attack helicopter power supplies that passed final test in Seattle, but flunked in Atlanta, sent back to Seattle and passed, sent back to Atlanta and flunked.

That was simply a case of tolerance build up in resistance with processes that traceable to NIST.
http://www.nist.gov/

In the 1990s I was working at a company where all 200 engineers went from designing electronic medical products to validating and verifying parts receiving processes to satisfy the FDA that human lives were not at risk.

I learned how painful it can be to prove that the simplest measurement is correct. Coincidentally my wife was designing calibrators at that time and spoke the language.

So when I look at the budget and process of how pressure is measured in guns shown in the pictures in load books, it is like looking at a caveman on a dirt floor holding his thumb up next to something to judge it's size.

 

[RC20]

But generally reliable. Some things that are simple work best.

Fortunately there is a lot of latitude for the most part. Bad data stands out.

One of my favorite though it was also tragic ones is the guy in the helicopter factory making shafts who ran out of the approved cleaning material.

He used a scotch brite pad which was also there but used for a different process.

Upshot was that it caused micro crack and the shaft broke over the North Sea.

Some things have NO tolerance and others no big deal.

Reloading is one that is not generally picky but it will bite you if you push the boundaries (upper end mostly).

I saw the end result of a Model 70 Winchester blow up a while back. Reloads we think. The gas did not do what it was supposed to in a more modern gun, blew the top off the receiver, shucked the barrel down range 20 feet and the scope went sideways.

Usually a failure of any kind is a cumulative series of events. for guns a Hot reload, something not right with the gun, chamber modified but not right, too much headspace etc.

 

[golfballshootr]

Thanks for the feedback gentlemen, I feel, as I infer from the information, that my initial answer is the correct one. With the caveat, that there are variances due to difference in standards and QC per company.

I don't mind giving information to the new, sometimes younger folks, to hand loading, but I don't want to give wrong or, misinformation.