Quote Originally Posted by 4end View Post
Having seriously looked at Ballistic Coefficient and any benefit it can produce for air gun use, it appears there is no constant BC for any same brand pellet. Minute differences in weight can alter the BC as can velocity so what is the point of persisting with its use. Consider that velocity variation is common even in PCP's fitted with a regulator, a springer with its wider variation has less chance of consistency, add to that any weight or dimensional difference, BC has little chance of being a constant that has any worthwhile benefit.
Having shot many different rifles over a 60 year association with them, I believe the only true way to set up and hit long range targets is with trial and error, perseverance aided by a little Strelok Pro on a still windless day recording the scope turret settings for future reference. I look at BC, weighing pellets, washing and resizing them, barrel harmonics, barrel cleaning etc and think what its all coming. If you believe all this is necessary then the days of loading your favourite pellet into your favourite rifle are numbered as you will need to check some computer app before proceeding.
99% of the factors you are talking about produce minute changes in BC, which will have no effect on computed trajectories. Weight will only affect the sectional density. If your velocity variation is so high as to change the pellet BC, even with the wrong reference drag law, you have a lot more than BCs to worry about. Again, any dimensional differences will have to be pretty severe to make a real change, particularly after the pellet has been squeezed through a barrel.

The biggest causes of changes in BC are experimental technique, not taking into account atmospheric conditions, and use of unsuitable reference drag laws.

I am no lover of the BC system, particularly for long range shooting. For accuracy of predictions, the use of purpose drag laws is much more accurate but, unless you can produce them yourself, there are none available.

But again, no-one is saying using a trajectory model will immediately put you on target, even a large gun's fire control cannot do that. It will put you in the right area to start the process of setting up your sights for long range, thus getting rid of a lot of effort and pellet waste, but the models need to be used correctly, which unfortunately is often not the case.