Powley Computer on the web...

[AZ-Stew]

Am I the only one who didn't know this was available?

http://kwk.us/powley.html

Enjoy,

Stew

[Dixie Slugs]

Always remember Homer only worked with IMR powders. The computer has a 15% ratio of powder to water...and is the average density of IMR powders, except 4227 and 4198. That 15% is not some kind of safety margin that some people think! I talked to Homer a few weeks before he died. His mind was alert and clear to the end. He did express concern, as I did, that many people did not understand what the 15% was.
I have used his sliderule type computer for years in designing loads for established rounds and wildcat rounds.
Regards, James@Dixie Slugs

[Nueces]

Thanks, AZ, I didn't know about it. I've got a couple of slide-rule versions, but I'm glad to have the site as well.

Mark

[4570guy]

I recently cross checked several loads for IMR powders in the .30-06 and .270 Win with book loads using this websight's calculator and they were spot on. Just for grins, I also checked some Krag loads (which the calculator is NOT supposed to work all that well for) and they were good as well.

[Harry O]

Yea, I knew it. I have and have used the slide-rule version for many years. In the early years (this was before chrono's became widespread). I used it to work up many loads. After I got my first chrono, I found that the calculations from the Powley were unbelievably accurate. Of course, I was using IMR powders, but even so, I had some chrono readings that were within 10fps of what was calculated. I don't think that any of the ones I tested were more than 50fps off.

[4570guy]

I've recently been playing around with regression curve fitting load data from a number of books, together with my personal load data, for the powders and calibers that I use. I've found that the regression curve fit models that I've managed to generate are quite accurate. This is essentially what Powley did, only over a much wider range of data. The truly amazing thing is that he did this before the day of the inexpensive PC. THAT is impressive!

[Harry O]

4570guy: I did some playing around with numbers myself. One thing I found interesting is what I call the "wisdom of the masses". I have a bunch of different loading books. What I did was get every load I could find for a given bullet and powder and plotted them on a graph.

There was the usual shotgun spatter of points. Then I laid in the least squares straight line (easy with computers nowadays). Then I tested several points on the line with my chrono. The results were remarkably close even though the original points were in all kinds of different guns, different barrel lengths, and tested with different chronos. Tere were lots of individual points above and below the line, the line itself was right on.

[4570guy]

HarryO: Yes, those least squares fits work out well. I too tried what you are talking about in using data from several different sources in order to provide sufficient data for a good curve fit. Interestingly, the higher order surface fit I obtained for muzzle velocity gave me an R^2 goodness of fit of .927 -- pretty darn good I thought. The software that I'm using is basically doing a polynomial least squares fit for "n" independent variables, where "n" can be any number. I was using powder burn rate number as one of the independent variables as a start. I was surprised it worked out as well as it did as I know the burn rate numbers are not gaussian, but ordinal and clump various powders together -- it worked out okay though.

[Dale53]

My head hurts!

Dale53

[leftiye]

Yeah, and I'm getting "gauss" pains!

[4570guy]

Sorry -- [smilie=1:.

[Larry Gibson]

No need to be sorry 4570 guy, some just have a hard time with a scientific approach to loading.

I used the Powley Computer along with the Speer Balistics Calculator for some years back in the late '60s and early '70s. When I got my first chronograph, an Oehler M10 with M61 Skyscreens i quickly found the Powley Computer was not that far off. It was actually pretty close many times. I still have both and occasionally use them when working wiith a new cartridge. There was an article by one of the major gun writers (may have been Powley himself) that correlated ball powders to the Computer. I wrote those on my Computor but unfortuneately did not save the article. There was a caveat with ball powders that they peak out at higher pressures much quicker than do IMR type powders. There was a graph in the article showing that while IMR type powders have a linear rise ball powders do not.

The Powley Computer and Speer Balistics Calculator still are useful but the computerized versions are more useful (and probably more accurate) than the older slide rule type. I'll keep mine at any rate.

Larry Gibson

[leftiye]

So, Larry, How scientific was your barb? I'd kinda hope you could keep your bad manners to yourself, and not take your problem with you all over the site.

[waksupi]

You guys play nice, please.