View Single Post
Old 08-24-2013, 12:38 PM   #47 (permalink)
CarmatechEng
Newbie
 
Join Date: Feb 2012

Testing

This is a great opportunity for all parties involved to discuss and dialog about these projectiles and paintballs in general. My opinions are just that, and they are derived from my experiences, conversations with firearms experts and performance testing. I will summarize the test that was performed; however, I will neglect product specifications and technical matter regarding our rifle and technology.

TEST PREPERATION:
Below is a list of the equipment and atmospheric conditions on the date of testing.

ATMOSPHERIC CONDITIONS:
Temperature: 84-86 Deg F
Skys: Partly cloudy
Wind speed: 3-5 mph
Wind direction: 9 o’clock
Humidity: 60%
Elevation: 845 ft
Elevation change between chronographs: < 6 inch

EQUIPMENT:
Chronographs: Competition Electronics light sensitive, Model # CE13800 Accuracy 1%
Rifle: SAR12 production model
Barrels: 16 inch Custom Products 2 piece barrel, 10,14,20 inch HH barrels
Light diffusers: 10x10 pop up tents
Linear Measurement: 150 ft tape measure
Elevation Change: Water level
Projectiles: FS rounds, Valkan Graffiti

TEST SETUP:
Fortunately we had the opportunity to set up our testing with a large woods at the 6 o’clock position and fully grown field corn to our 9 o’clock. Both of these natural structures benefited greatly in reduction of observed wind. We chose a 100 foot stretch of land that was relatively flat. We used a water level to inspect elevation change and found less than 6 inches of drop in the hundred feet. Six inches of drop in 100 feet is not optimal; however, for this particular test it was perceived to be a minor deviation.
We covered the shooting position and the 100 foot chronograph with 10x10 pop up tents, as the chronographs being exposed to direct sunlight created substantial errors. Once covered with diffused light we proceeded to shoot through both chronographs (One at a time) to verify correct measurements were being acquired.
We then proceeded to send rounds through the set of chronographs using the SAR12 with 20 inch rifled barrel. We sent a minimum of 20 rounds through the chronographs with the 20 inch barrel. An observation was made that the velocity drop was very consistent across the board. It was very common for the FS rounds to cross the second chronograph with a velocity of 220 fps. We didn’t measure each rounds mass! Final results were barrel velocity of 299-301 fps, and 218-222 fps at 100 feet. This gives us a BC of .0152 GA.
We then switched the rifle over to the Custom Products two piece 16 inch. Bore was very similar to HH20. Re adjusted the regulator to shoot 300 fps at the barrel. Sent another 20 rounds down range. Final numbers floated around 195 fps at 100 feet. This gives us a BC of .0115 GA.
Finally we decided to use the GA rather than G1 as G1 is based on more aggressive ogive designs. It has been expressed to me that the G1 modal is based on geometries that are exposed to supersonic flight. We went to the GA modal because the overall nose cross-section of pellets are in some examples very similar to the FS rounds. With exception to the waist design which is used to induce drag, thus stabilizing the round in smooth bore barrels. Very interesting article!


Finally my opinion about the Chronograph separation distance: I want to have the largest separation between chronographs because I want to find average BC values. The BC value probably decreases at range due to a slowing of the rotational velocity of the rounds. I am assuming that the spinning of the round from the barrel is reduced thus forcing the fins to create the spin from forward motion. This would then decrease at distance efficiency. I will be doing testing out to 100 yards to either prove or disprove my theory. I will be setting the at range chronograph at an angle parallel to projectile path and not parallel to earth surface. By doing this I eliminate the vector quantity that UV Halo is concerned.

Thanks
David Williams
CarmatechEng is offline   Reply With Quote