Next, I filled the case with water, reseated the bullet allowing the water to be displaced through the groove I had filed, and weighed the assembled cartridge. 17's powder chamber by pulling a bullet, dumping the powder, filing a small groove along the length of the bullet, and then weighing the two in grams on a PACT electronic scale. To check expansion ratio, I measured the volume of the little. 22 Long Rifle, had a high expansion ratio and expected similarly to find a barrel length near 18 inches where velocity would be highest. 17M2's small powder chamber, I assumed it, like the. A line graph of those results is shown nearby.īecause of the. There was no "blip" in velocity like I had with the previous barrĮl, and velocity appeared stable between 16.5 and 23 inches of barrel length. This time, muzzle velocity appeared to increase steadily as the barrel was shortened until a barrel length of 23 inches was reached. This time I also cleaned the bore thoroughly between groups of shots using a Hoppe's BoreSnake, fired one fouling shot before recording velocities for each group of shots, and used an indicator on the shooting bench top to make sure that regardless of barrel length, the muzzle was always at the same distance from the "start" chronograph screen. I also made it a point to control my variables a lot better by crowning the muzzle between cuts using a brass round-head screw and valve-grinding compound in a cordless drill. Physically, that little increase in the velocity can't occur, and indeed when I checked the data using Tioga Engineering's Baltec1 program, it showed that the blip in velocity was not statistically significant and might not have actually occurred.īlip or not, I decided to repeat the test using a special 27-inch barrel T/C made for the occasion and to fire 20 shots per inch of barrel to try and lower the standard deviation. By the time I had the barrel cut to 17 inches, velocity appeared to be going back down. With each inch, velocity declined until I got to 20 inches, then velocity appeared to climb again. Using an Oehler Model 35P chronograph set up with four-foot screen spacing at 15 feet from the muzzle, my procedure was to chronograph and record five shots, then clamp the barrel in a Wheeler Engineering barrel vise, cut off an inch using a hacksaw and record five new shots. 22 Long Rifle, so I started with a 23-inch factory barrel. 0176 in3), I assumed optimal length would also be about 18 inches, as with the. 17M2 has such a small powder chamber (it measured. So all this brings me back to the Contender project and cutting off its barrel in one-inch increments and how the velocity changed as a result of it. In other words, it has a very small powder chamber relative to the bore. Regardless, the reason for the bullet slow down at that short a barrel length is because the expansion ratio (the sum of the volume of the bore and powder chamber divided by the volume of the powder chamber) for the. 22 will vary from one load to another and one gun to the next because of different powder charges in the loads and tolerances in the bore dimensions. 22 Long Rifle, and from those experiments it has been concluded that generally any barrel length greater than 18 inches is actually causing the. Published experiments on how barrel length affects muzzle velocity have been done with the. But the project also presented an opportunity to cut the Contender barrel off in one-inch increments to see if there was an apparent optimal barrel length for velocity that I could ascribe to the little. In fact, the R55 produced slightly higher velocity. The purpose of the amputation was to compare muzzle velocity of the fixed-breech Contender to that of the R55 autoloader to see if there was any significant velocity loss from the self-loader.
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