Doug,
Today I did an experiment I tested the velocity ( speed ) in several different pellets in two of my airguns with a chronograph. I measured the muzzle velocity and the velocity at 35 meters. These are the average results ( 3 shots per test ):
Cinetic energy: 1/2 . m. v2
Diana 45 T01 .177 4,5 mm
Gamo Match ( 7.5 gr ) :
muzzle: 276 mts/s 35 meters:178 mts /s ( % of veloc. reduction: 35,5 %). Cinet.energy:1188 J
- The wadcutter Gamo Match .177 showed a big velocity reduction. The wadcutter shape is not good at 35 meters. But, paradoxically, the wadcutters RWS Meisterkulgen .22 showed the same % of velocity reduction than the Superpoint and Superdome; why this discrepance ?.
- In the .177 caliber, at 35 meters, the RWS Superdome retained more velocity than the others, Superpoint and Gamo Match.
- In the .22 mm caliber, the Meiterkulgen, Superpoint and Superdome suffered almost the same % of velocity reduction at 35 meters. The JSB Exact retained much more of its velocity ( and cinetic energy ). This is wonderful .WHY ??.
- Is it correct to express the cinetic energy as = 1/2 m.v2 ?
- Is there a positive correlation between velocity and flat trajectory ??. For example the Superpoint weights less ( 14.5 gr ) than the JSB Exact ( 15.9 gr ). We assume that the gravity will affect more the Exact than the Superpoint, which is lighter. Nevertheless, the velocity at 35 meters is much faster in the Exact. Which one will have a flatter trajectory, the Superpoint or the Exact ??.
1.- The strongest decelerating forces in a pellet's flight are induced by the "parachute / shuttlecock" effect of the vaccuum behind the skirt. The shape of the nose is not that important UNLESS the shape of the nose makes the airstream close BEHIND the skirt, in this way, the skirt is not actually sucking up the energy in the pellet just to let the pellet fly through. That is why between two similarly bodied pellets RWS Meisterkugeln/SuperPoint/Super Dome, the nose shape makes little difference.
2.- When you cross the line of basic architecture (slimness ratio, place and shape of waist, size and girth of waist, curvature behind the head, etc, etc, etc) all bets are off. The match pellets are designed to be as accurate as possible within 10 meters and then to cut a nice neat hole, everything else is superfluous. Domed pellets are aimed at the longer range airgunners. Superpoints ar peculiar beasts, their sharp point makes it easy for the air to open, but also creates a fast closure just at the point where the waist narrows, this creates a vaccuum and friction, so SuperPoints should not be used for long range shots in your gun.
3.- The JSB pellets are among the best pellets in the world. The shape of the nose makes for a good penetration through the air at subsonic speeds and the air does not close behind the head as much as with other pellets, I've found that the 0.177" new model heavies (10.12 grainers) actually behave almost like a 14 grains 0.20" cal. pellet, the 0.177" mediums (8.44 grainers) behave almost like an 11 grain 0.20" cal. pellet. In 0.22" the Exact Jumbo's have as good a performance at 16 grains as pellets weighing 5 grains more. JSb pellets are really, really good. There is a lot of research and testing done on those designs.
4.- KE is 1/2 M V V, if this is what you meant, you're correct.
5.- Yes, there is a positive correlation between Velocity and flatness of trajectory the higher the velocity at all points, the flatter the trajectory. A trajectory is the result of two things happening at the same time: horizontal translation and vertical fall. If the translation happens faster, there is less time for the falling. Simple really. Gravity does not affect heavy things more than light things. Galileo demonstrated that heavy objects fall at exactly the same speed as light objects.
6.- The JSb will be by far (about 1" at 35 yards) the flattest shooting of the SuperPoint/Exact duet.
I have tried a simple test of certain pellets by aiming at an object across a 250 yard pond (very low tech, but it works!) The difference between the distance the pellets traveled was hard to believe. The JSB's were so much more efficient, you'd have to see it to believe it. And when it came to how the pellet stayed on course, again the JSB's were far superior. This may not suprise some of you but, at 150 yards, the JSB's would reach out to a rock I was aiming at with a simple adjustment of elevation on the rear sight, no hold over was required. I can not say that about the others pellets used, they fell way short. I had no idea that the 350 was capable of of shooting a pellet that straight at that distance. I guess that's why It has always been my "go to" gun!
Hector, thank you very much for your very technical info. We would like to have you working here in Argentina !
Doug, your field observations are very useful.
I´m talking with the JSB factory: they are very informative.
I´ll use JSB pellets for my airguns; I don´t know what I´ll do with the thousands of RWS that I´ve alreadsy got !
