Optimal pellet/slug speed related to distance to target

[Floris]

Hey all,



Optimal pellet speed related to distance to target



Ive been “tuning” my impact and Dreamline over the last couple of months and learnt a lot about many things. Last interesting bit I read was about the transfer port mods and efficiency. I was testing yesterday with shooting 18gr JSBs with 880ft/s but with different settings using the transfer port on my dream line.

This got me thinking about speed of the projectile when leaving the barrel and when at the target. I see many questions about the optimal speed of different pellets and slugs but these are never related to the distance the shooter wants to use them.

I could think of reasons that if you are shooting long range (eg 100m or further) you would want to shoot a projectile faster then when shooting short range. My reasoning behind this is to have higher speed when at the target closer to the optimal speed and better trajectory. When I shoot slow I see my groups opening up and as pellets lose their energy fast. This is not about hitting power but about accuracy and precision.

Has anyone thought about this or an opinion?

Thanks

 

[nervoustrig]

For each projectile, there is an optimum muzzle velocity that will provide the best average ballistic coefficient. For domed pellets, that’s usually in the vicinity of 800-900fps. 

Slower than that and the BC suffers, and ranging errors will also have a disproportionately larger effect.

Faster than that and the BC suffers, and there’s a greater chance spiraling will develop at extended ranges.

To put it into context, these considerations are useful for achieving incremental improvements after you’ve moved past the basic accuracy of the hardware…the quality of the barrel and the pellets and how well they are matched, and the capabilities of the shooter. 

Seeking to optimize the BC is not just a theoretical advantage. If we look at the state of tune for most competitor’s airguns, they’re almost always in that velocity range. However for someone like me who just enjoys airguns, there’s plenty of accuracy to be found at many different velocities so generally I don’t get too hung up on it.