Posted by Tim Kraft on August 30, 2000 at 12:51:57:
Over the lifetime of one tank of air on your typical air pistol, what is the speed variation for shot number 1-10 vs 110-120 for a tank that is supposed to give you 120 shot??
The reason for my question is that the flight-time difference translates directly into a pellet drop difference. For example, if your gun starts out at 450 fps and drops to 410 fps, the impact point will be over 5mm lower!!
I don't have the equipment to test speeds, but I know some of you out there have done this.
Posted by Roly on August 30, 2000 at 16:26:56:
Last winter I did an extensive study using an LP10 to test about 10 different pellets. The astounding thing I found was not what I was looking for. I was testing for an accuracy variable among the various pellets. What I found during testing was that the amount of CO2 charge had a greater affect on accuracy than any variation among the top pellet brands/weights.
In summary, a full cylinder weighs 204 gr. and I used to fill to the limit. But when I do there is a 25fps plus or minus variation in pellet speed for the first ten grams. In addition the first 5 grams or so tend to put out faster average speed pellets than the next five grams. Then the curve flattens out with negligible variation.
The ambient air temp was 65F during the test. My gut feeling is that results will vary with ambient temp.
The lesson for me was to pick a good pellet, then never fill beyond 190 grams.
Posted by tim k on August 30, 2000 at 18:21:53:
I saw that article published somewhere, and in fact that is why I did the calculation. A difference of +/- 25 ft/sec equates to +/- 2.5 mm in verticle separation at the target for a mean velocity of 430 ft/sec. Clearly the regulator on your gun was not providing adequate regulation when the tank was near maximum capacity. Are other guns equally unreliable in their first 20 shots of a maximally filled scuba tank? It would be difficult to repeat your study, but many people check the speed of their gun. So I am wondering if anyone has check the speed, and thus the quality of their regulators over some range of tank pressures.
Posted by Andre on August 30, 2000 at 17:54:12:
Most air-pistols use regulators, and have built-in systems to prevent you from firing when the cylinder pressure drops below minimum functional. The morini 162 locks the breech, while the FWB P-34 purges the cylinjder when pressure gets too low. The Pardini K2 doesn't have any of these systems, so you'll just have to watch the rings at the front of the cylinder.
I shoot a CO2 pistol myself. I've found out that I can shoot about 120 shots without loss of accuracy at 90% of the cylinder's maximum capacity. So I don't overcharge and don't go beyond a 120. Simple as that.
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