Stan;
The data I have was cited by Burrard. unfortunately, when I was entering chemo back in Oct of '17 we had to do some re-arranging of the house. Somewhere, Somehow my copy was misplaced & has not been found yet. I Fear the Worst, that somehow it got in the trash. "The Absolute Best Book" I have ever had on shotguns.
I will do the best I can from memory. A heavy pendulum gun was made up with as I recall a 24" barrel. This barrel was fitted with a crusher pressure sensor. Barrel extensions were made up to around 32" as I recall with each one very carefully fit to within a couple of Ten Thousandths of an inch (.0002") & carefully lapped in for no step in the bore. The two of interest for this discussion though were two 30" total lengths with one Cylinder bore & one Full choked. Loads were loaded using several powders all in the nominal 2˝" chambering & with the nominal British Game load & Velocities were recorded at the customarily observed vel over 20 yards & the recoil recorded. Interesting thing was that within each barrel recoil varied according to the velocity of each individual load as would be expected.
What was Not expected was that while the observed velocity was slightly higher for the Full barrel than for the Cyl barrel, the Recoil Reversed with the Cylinder barrel showing a very slight but consistent increase in recoil. So far the only explanation for this was the cylinder barrel was giving a very slightly higher velocity than the Full barrel. What could account for this other than a slight checking of the shot upon hitting the choke?
Nota Bene (Note Well) I consider Don to be one of the very most knowledgeable posters we have here & I have learned a tremendous amount from him over the years. Never-The-Less I am not thoroughly convinced that solid shot behaves identically to a liquid or gas in passing through that venturi.
Also in the early days of choke boring, many barrels had very thin muzzle walls. Problems were soon encountered with bulges at the choke or as the Brits called it Lifting the Choke. This would tend to indicate a slight checking of the charge & the creation of an obstruction shock. Most did not bulge but simply had a slight ring bulge at about the beginning of the choke.
If anyone has any data as to what is the absolute closest to the muzzle it has been possible to record velocities I would like to have this knowledge. The difference in absolute muzzle velocity & that at even 2 or 3 feet is easily accounted for by the speed at which the shot from the cylinder bore disperse & drag affects the individual pellets rather than the whole charge reacting more like a solid projectile from the choked barrel. All I've got at the present.
Sure Wish I could find that "The Modern Shotgun" book. The Most Valuable book I have ever owned in my entire life is "The Holy Bible" but this was the most valuable one I ever had relating to shotguns, & not just from a monetary sense but the value of the information therein.
Last edited by 2-piper; 06/17/19 10:09 PM.
