QuickLoad cartridge data for polyonal rifling

[cwsanfor]

QuickLoad, at Data: add, load, change, save> Case/Caliber data> Change data records in active file> Cross-sectional bore area> Calc lets you select "HK Polygon Rifling" or "Normal Rifling". If you select HK Polygon Rifling" you must input Caliber (groove", Caliber )bore), Larger Radius R, Small Radius r, and Number of Grooves.

I may be overthinking this, but under the assumptions that polygonally-rifled barrels actually perform differently than conventional ones, that "HK Polygon Rifling" (although I believe HK's are octagonal rather than hexagonal like the Glock) is similar to Glock polygonal rifling, and that QuickLoad effectively uses this data, I'd prefer to have data there that matches my Glock 19.

I can't find the groove or radius data anywhere. Do any of you know the correct values for the Glock's "lands and grooves" (sic)?

Thanks.

 

[918v]

Those values are prolly proprietary. I once tried to get those values from Walther and was basically told to F-off.

 

[ngnrd]

Why can't you simply measure it?

 

[918v]

How would you measure it?

 

[W.E.G.]

Here is what you do.

Load up some ammo.

See what Quickload gives you for velocity numbers using the default cross-sectional bore diameter.

Shoot the ammo over a chronograph.

If your chronograph gives you the same numbers as Quickload, you know Quickload is right on the money.

If you get different chronograph numbers, you have to tweak other variables on Quickload to get the Quickload velocity numbers to match the chronograph numbers. Cross-sectional bore diameter is one of the numbers you can tweak.

I find cross-sectional bore diameter to not make a huge amount of difference on the Quickload output. Unless you foolishly believe there is something to gain in performance by pushing your handloads to the limit, you can just use the default cross-sectional bore diameter, and live with the small differences.

 

[W.E.G.]

I also urge you to take Quickload data, as it applies to anything other than .308/30-06 with a grain of salt.

See http://www.frfrogspad.com/intballi.htm

There are some "mathematical" methods of computing a fairly close approximation of the actual internal performance (i.e.: chamber pressure and muzzle velocity) of a given combination of cartridge, firearm, bullet, and powder but their details are beyond the scope of this page. The "Powley Computer," a slide rule type device was at one time available and gives rather good results when used with the "IMR" type of powders and cases of similar capacity to the .308 and .30-06. It is based on some mathematically derived "constants" developed at Frankfort Arsenal which provide a close approximation to the results derived by some rather complex mathematical gyrations. Several computer-based adaptations of these calculations are available from different sources (such as QuickLoad) and all suffer from the limitations of being based upon the Frankfort Arsenal model of the .308/.30-06. As far as I know the Powley Computer is no longer available although Powley's code has been privately adapted to computer use by various people. As mentioned previously these computations are based upon case capacities and pressures in the .308 Win & .30-06 range. For cartridges of significantly larger or smaller capacities, or lower pressures, the result will be not be accurate and can frequently be dangerous if you don't understand what is what.. For some information on the Powley Computer you can visit the following web site thanks to Nels Tomlinson.

http://geocities.com/nelstomlinson/sliderules.html#powley