I've read a whole lot of opinions about making the best homemade (stefan) darts on the discussion boards. What really bothers me is the blatant disregard for the scientific method. I'm tired of people trying to explain why this type of "air pocket" is better or that type of depleted uranium weighting prevents "spin-out". What it all comes down to is which dart goes the farthest right?
Well, I sat down to answer the whole air-pocket question conclusively. A bunch of people maintain that darts need a hole in them to "trap" the air coming out of the gun. This is of course crap. If anything, that pocket of standard pressure (1 atm) air is going to increase the volume that the high pressure air must expand into - thus lowering the pressure behind the dart as it exits the barrel. That being said, there's a possibility that drilling or melting a hole in the back of the dart shifts it's weight balance enough to be beneficial.
Since my guns are all modified to use micro stefans, that's what I made. I made 4 types of 2.5" dart and one 1.5" to throw in a quick length comparison. The four varieties (in order) are: nothing done to the back of the dart; 13/64" hole drilled halfway down the length of the dart (taken from Stefan's original); a 3/4" long hole melted in the back of the dart with a soldering iron; a slightly "tapered" dart with the back end melted and rounded off somewhat - an attempt to make it more aerodynamic. The short darts have nothing done to the back. I made two of each so that inconsistencies in manufacturing wouldn't throw off the numbers too much. The tips are color coded to help me easily distinguish them during field testing.
I shot each dart three times from my modded SM1500 for a total of six shots with each dart body type. I figgure this is a pretty good baseline gun as it's very popular and is an excellent all-around gun. All shots were fired level, with the same barrel of the gun, pumped three times. I get slightly better range with four pumps but it leads to greater variance in groups so I stayed conservative. The results are below. I measured variance in groups in order to quantify the consistency of each dart type. Lower variance should make for a more "reliable" dart.
Dart Type Avg Distance (feet, inches) Variance (Max - Min) 1 88', 10" 215" 2 84', 10" 461" 3 88', 7" 125" 4 81', 8" 293" 5 86', 11" 213"
All of the darts had similar flight characteristics and were equally accurate except for type 5. The smaller dart took longer to achieve a straight flight path and was somewhat less accurate. While body type 3 demonstrated greater distance consistency than the other darts, I'm not entirely sure the difference is statistically significant given my small sample size and great variance among the types. What is clear is that there is no distance gain as a result of modifying the back of the darts.
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