RIFLED BARREL TESTING RESULTS!
Successfully tested--Rifled PVC launcher barrels.
Static and pseudo-dynamic pressure testing demonstrated the structural integrity of the pipe is quite high, up to the design limit, to withstand any launching pressures. See the results of this test below.
- STOCK: 1 1/2" diameter SCH40 PVC water pipe 330 psi rating
- BORE: 1.582" before modification LANDS: Standard six equally spaced angularly.
- PITCH: 1 complete turn in 60 linear inches of travel
STATIC LABORATORY TESTING:
Test method: One specimen one (1) foot in length, processed with six lands symmetrically placed around the inner bore.
Specimen capped with SCH40 PVC caps glued to each end, one cap already drilled/tapped to receive charging stream. After glue had cured over 24 hours at room temperature, a high pressure hose was connected through the barb fitting in the cap. High pressure room temperature 3.9 grade nitrogen was introduced slowly, while the regulator pressure gauge was observed. Pressure rise rate was approximately 30 psi/minute.
When pressure reached 320 psi and held for several minutes, it was bled out. Then the sample was recharged in about 5 seconds, fairly quickly, to 320 psi. Again, held and bled, then recharged very rapidly (<1 sec) to 320 psi. Nothing hapened--the pipe was still capable of sustaining its design load under the testing conditions. This was all done inside a 4" 5000 psi autoclave in case it did decide to fail.
Range testing has been performed on the various barrels, results as given below. Only ten rounds were successfully recorded for each type, due to time restrictions and hungry cattle on the test range (no, we didn't shoot any of them).
Since the target was only 4'x8' in size, sometimes a highly asymmetric potato would veer off dramatically (a miss)--this data point could not be accurately recorded. A note was made however about how many rounds exhibited this behavior, each potato loaded pretty much the same way from the muzzle with a pusher stick.
- Ambient Temperature: ~75F
- Light and Variable Wind
- Target Range: 115 feet
- Target: Two layers of old crusty 1/2" CDX plywood, 4'x8' size
- Launcher Anchor: Two forged steel fence posts Launcher cradle of a recessed board, entire assembly rigidly lashed to forged posts
- Chamber volume: 252 cubic inches (~1 gallon)
- Barrel Length: Both 36" in length
- Same chamber, 2" threaded interchange used
- Fuel: ~6 cubic inches of propane, metered with pressure regulated constant volume device
Enough with that, the results!
First the smoothbore 'regular' barrel, at 115 feet, several warm up rounds fired to get the system up to 'steady state.'
Rounds fired: 14
X-axis standard deviation: +/- 13.6 inches Y-axis standard deviation: +/- 21.6 inches (4 Total misses)
And for the rifled pipe, six lands, the results are dramatically enhanced. Far tighter group, and only one miss.
Rounds fired: 11
X-axis standard deviation: +/- 6.7 inches (51% improvement) Y-axis standard deviation: +/- 11.2 inches (49% improvement) For a 50% increase in accuracy! (1 Total misses)
Upon inspection of the rifled barrel, the 'spud streaks' were evident and parallel with the riflings. I was using a perfect propane load in an oversized chamber every time, which was VERY loud! If you don't believe me......Check out the independant testing done by one of my customers.
document created 7/7/2002 3:28:05 AM;
last modified 8/29/2008 8:19:52 PM