Ballistics by the inch

How I spent my vacation.

So, all last week we were finally conducting the Cylinder Gap tests. For this test alone, it was over 6,000 rounds. I thought as part of documenting the whole process I’d share a buttload of images and a brief description of each.

Given the size of this sequence of tests, we knew we needed to make a number of upgrades to our equipment and set-up. Jim Kasper did most of this work in advance. The Ransom Rest was mounted to a plywood platform which fit perfectly over one of the banquet tables, so we could just snap it into place each day.

To minimize problems with getting good readings from the chronographs, Jim K built a framework to support 250w lights which shined down into the sensor positions. After a couple of hours use, we decided to adapt a fabric panel from the new EZ Up we got to protect the chronos from weather as a diffuser.

Jim K also built a couple of racks to hold boxes of ammo. That way we didn’t have to sort and arrange everything each morning – just make sure the racks were filled before we left for the site each day, and then draw what was needed as we did the testing.

We had to run the generator continuously, so as to power the lights for the chronos. I designed a simple sound box out of 2″ construction insulation which would go together with a little duct tape, and would shield us from the excess noise while allowing the generator to operate.

The test platform was an Uberti Single Action Army clone in .38/.357. For other reference points, we also tested a number of ‘real world’ guns – shown here are a 2″ Chiappa .357, a 16″ Winchester 94 AE lever gun, a 4″ S&W 586, and a 3″ Bond Arms derringer. In addition we used a 1.875″ Ruger LCR in .38, a 1.875″ S&W 642, and a 6″ Python.

The Uberti worked remarkably well. We used a Ransom Rest in order to give consistent aiming and minimize hand trauma (when you’re going to shoot 6,000 rounds in the course of a week you’re going to suffer if you actually do it all by hand.)

Each day we’d take the lights, the chronographs, the guns, and the ammo home so as not to risk theft.

Our backdrop, same as with the previous tests, was a wall of railroad ties that is part of an old cabin. We used fresh-fallen Locust logs as a target, going through one or two 18″ logs a day, and replacing them as they got chewed up from so much shooting.

As we emptied boxes of ammunition, they got tossed under the tables, out of the way. All the cardboard was latter flattened and recycled. The plastic and styrofoam, unfortunately, was not. I must admit, as much as I like Buffalo Bore ammo, I hate their oversize boxes.

After we finished a round of shots, doing all of the ammunition with a set cylinder gap, we’d unscrew the barrel, change the shim (which changed the cylinder gap), and then did another round. With the Ransom Rest mounted in position, and the gun mounted in the Ransom Rest, there was an accumulation of gunpowder and particles from the cylinder gap. You can see this in the marks on the board under the gun, as well as the discoloration of the foam on the ‘blast shield’.

Here’s another shot which shows the gas/particle effect, with Jim Kasper in the background, a clipboard ready to record more of the chrono readings.

After we finished all the cylinder gap testing, we did the classic BBTI ‘chop tests’ on .223 Remington and .460 Rowland.

Even with the Ransom Rest, and using a Weaver Rail with a laser sight, it was easy to allow shots to creep up a little too high. In this case, the fabric used as a diffuser over the chronos served as a warning before we hit any of the lights.

7,000 rounds is a *lot*. Here’s a shot of a bucket about half filled with spent brass cartridges, taken towards the end of the testing. And this was the second of these 5-gallon cat litter pails used (the first was filled completely).

Testing the .223 Remington cartridge was the first real rifle round we’ve tested. The protocols we decided on were a bit different then in our previous chop tests of handgun cartridges. But we did go ahead and get down to a 3″ barrel, since we had a Bond Arms derringer in 3″ in that cartridge to test as a reference – this thing only has about a quarter-inch of rifling in the barrel. And it made a most impressive fireball when shot.

Just for giggles, we chopped the .223 barrel down to 2″, to show what would happen if you tried to go to that length. Here’s the result:

That should give a sense of what it was like this round of tests. I’ll have more to say about the testing, but thought it would be fun to share the images right away. We hope to have the data crunched and ready to post sometime later this month, but watch this blog for some previews.

Jim Downey

May 9, 2011 - Posted by | .357 Magnum, .38 Special, Anecdotes, Data, Discussion., General Procedures


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