I tend to think of the optimal velocity like Bob described, being relatedness to the pellet’s wind drift sensitivity. However most of my shots are inside of 60 yards and we don’t have a lot of wind so it’s not something I have to obsess over.There was just one other thing I wanted to mention which is associated with the velocity and that is barrel harmonics. Vibrations induced during the shot cycle couple into the barrel and cause it to vibrate. This vibration translates into some degree of dispersion of the groups. An exaggerated way to visualize it is to think of the barrel being an elastic tube flapping in the breeze. Depending on where the muzzle is just as the pellet exits, the shots will disperse to different points of impact. With a well behaved barrel, that dispersion will be small...but by varying the rifle’s state of tune, you change both the excitation forces and the time at which the pellet reaches the muzzle. In so doing, it may either improve or worsen your groups so it’s a worthwhile thing to experiment with. This is also the sort of thing that is being manipulated when groups are improved by either relocating a barrel band or adding another one, or conversely, removing a band to free-float the barrel. There are also accessories sold as harmonic tuners that slip onto the barrel and can be moved fore and aft to achieve the best result.Fortunately, much of the time things like wind and biological factors make it all but impossible to discern any improvements but there are some cases where it makes a big difference.
Greg, while higher velocity does decrease the time to target, that is NOT what produces wind drift.... It is a hard concept for most to grasp, but the wind drift is proportional to the DIFFERENCE in the time to target in the real world, compared to a vacuum.... This LAG TIME, coupled with the wind speed, is what matters.... Since bullets flying Supersonic have a much greater drag, even though they are going faster, their lag time is greater, and so is the wind drift.... I think the concept that higher velocity equals less drift comes from PBs where if you compare on that graph, say, 2000 fps to 3000 fps, in all cases the higher velocity has less drift.... However, you will note that below 1500 fps or so, that is not true, and in fact the least drift occurs at around 850 fps within 50 yards, increasing to about 900 fps at 100 yards.... Whatever velocity produces the least lag time from muzzle to target for your pellet will produce the least wind drift.... Since doping the wind is the most difficult part of long range shooting, because as you say, the trajectory can be calculated (it is mostly velocity dependant, BC only plays a small role)…. IMO staying just above the velocity that produces the lowest lag time to target is the best, from an external ballistics point of view....Bob
PCP airguns use a lot more air to propel projectiles faster than about 1000 fps.... They are more efficient at 800 than at 900, and much more efficient at 900 than at 1000.... Over Mach 1 it takes a LOT more air to get there, and then you watch the projectile lose all that hard-earned velocity in the first few yards....For the above reasons, I think that the optimum range of velocities for airguns is 800-950 fps for pellets and 800-1050 fps for bullets.... The only way to find the BEST velocity for YOUR pellet/bullet is to test it.... but I recommend you stay within the above ranges....Bob
For the above reasons, I think that the optimum range of velocities for airguns is 800-950 fps for pellets and 800-1050 fps for bullets.... The only way to find the BEST velocity for YOUR pellet/bullet is to test it.... but I recommend you stay within the above ranges....Bob
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