Shooters Forum banner
  • Hello Everyone! Let us know what you would spend a $50 Amazon gift card on, HERE For a chance to win a $50 Amazon Gift Card!
21 - 32 of 32 Posts

·
Super Moderator
Joined
·
14,119 Posts
Interpolation takes values off a trendline inside the range of known good data points, while extrapolation takes values off a trendline outside the range of the known good data points. Extrapolation is more prone to error than interpolation because you can't know if there is an abrupt change in the trendline outside the measured data range, as when a powder is spikey on the high side of the known good data range or prone to squibbing out on the low side. A trendline taken from good data doesn't tell you that. The point is, In both cases, you depend on some known-good data points to determine a trendline from which you estimate what other good data points are likely to be. The problem with old data is you can't count on its good data points to have remained good over time, so you can't count on constructing a valid trendline from it for either interpolation or extrapolation.

This is not to say all old data has gone bad. The same 45 Auto loads of Bullseye that were good in the 1920s work safely with hardball today. I can think of a few others, but the point is not to blindly trust any old data, as some products have seen more significant changes.
 

·
The Hog Whisperer (Administrator)
Joined
·
38,161 Posts
Case capacity, bullet mass, and bore diameter don't "know" the age of gun, or the year the cartridge was invented. It's all pretty basic when you look at it from that perspective. Find two cartridges, one a bit less, and one a bit more case capacity, of the same bore size and there ya go, fairly easy to see what is realistic, and what is not.

Gigantic black-powder cartridges, that gets a little more difficult. Mostly due to lack of things to compare to.
 

·
Registered
Joined
·
462 Posts
After 40 years and I don't know how many cartridges I've worked up safe, accurate data, for which there never was any data, by extrapolation or interpolation that was a lot more than a supposition, with zero excursions, I believe I'll trust my experience and results rather than someone else's opinion of what extrapolation consists of.
 

·
The Hog Whisperer (Administrator)
Joined
·
38,161 Posts
Nick's 'opinion' of extrapolation isn't idle talk. It's a fundamental tenet of higher math. If you don't know the difference between interpolation and extrapolation, I suggest you don't get in a math debate with him ;)

How many of those loads that you "extrapolated" did you have pressure tested? Just curious. Do you have Quickload or any other pressure modeling software?
 
  • Like
Reactions: Darkker

·
Registered
Joined
·
5,356 Posts
I buy the Hodgdon annual manual every year and the Lyman one every 10yrs or so. Having had half a dozen wildcats that had little or no current data you get used to working up your own, if you can read micrometer readings at the web and interpret chronograph readings manuals are interesting reading and offer starting points. Hodgdon is the most common powder available around here so it's exciting to see what new "wonder" powders they introduce every year. Still waiting for that magic powder that will shoot a 140gr bullet 3600fps with 36gr. of powder and never burn the throat out!!!!!!
 

·
The Shadow (Moderator)
Joined
·
10,038 Posts
After 40 years and I don't know how many cartridges I've worked up safe, accurate data, for which there never was any data, by extrapolation or interpolation that was a lot more than a supposition, with zero excursions,
Then prove it. Start posting the traces supporting the claim about pressure. I'm suspicious that extrapolation of burning charts across various manufacturers and formulations has never had any excursions. You'd be ahead of many of the actual manufactures, if you can do that on anything beyond a couple one off attempts.
 

·
Registered
Joined
·
462 Posts
I have proven safe loads, repeatedly, to myself and many others. Obviously that isn't good enough for you but, you cannot possibly know how utterly insignificant your opinion or future post is.to me.
 

·
The Hog Whisperer (Administrator)
Joined
·
38,161 Posts
I think it would be fascinating to see actual pressure testing done on your "proven safe loads" to see how close your guessing, and reading of signs, got you to the end point. Hey, if you hit within a few percent of what you were targeting as pressure, I'll be severely impressed!!!!!
 

·
The Shadow (Moderator)
Joined
·
10,038 Posts
You made a claim about knowledge of pressures, I simply asked for the evidence to support that claim of knowledge. 🙄
 
21 - 32 of 32 Posts
Top