Hi all, in the sierra data they give different ballistic coefficients for different velocities for every one of there bullets, nobody else seems too, would these velocities be relative or very similar for other bullets. Swaro
I assume that the highest figures are max bc that bullet will be no matter how fast it goes.
There was a time when Dupont put out sheets of bullet "forms" so that a shooter could match his or her bullet to the form as closely as possible and plug in a BC so, in that sense, yes: It's relevant. Sierra A 150 grain Game King flat base probably has a very similar BC to a Speer 145 grain Hot Cor 7mm bullet based on a fairly similar form and weight.
It will be close, but not exact. For coarse work it's an OK starting point. For serious work, you won't even take Sierra's word and you'll calculate your own BC.~Muir
Ive tried the g7 bc on my bal cals and they are way off, g1 bc's are very very close to actual as I shoot out to 1000yds thats a good yard stick to measure with.unless I am doing something badly wrong with the g7 figures which I cant see what as all I am doing is changing from one to the other on the bal cal, not changing anything else.
Ive tried the g7 bc on my bal cals and they are way off, g1 bc's are very very close to actual as I shoot out to 1000yds thats a good yard stick to measure with.unless I am doing something badly wrong with the g7 figures which I cant see what as all I am doing is changing from one to the other on the bal cal, not changing anything else.
surely the only reliable way is to work out the BC for your chosen bullet at your chosen velocity over a suitable range
the further away from the muzzle the better
Possibly but as the drag on the projectile (bullet) isn't a "fixed equation" and depends on the velocity itself it could be fraught with issues.
You'd need to measure a series of velocity / range data for each velocity zone.
If the projectile stayed inside a velocity zone (such as well supersonic) then one could do the estimate given that the drag would be proportional to some fixed power of the velocity: make a few measurements at, say, muzzle, 50m, 100, 150m and some simultaneous equations.
However, if the projectile transitioned to a low sub-sonic or into the transonic / subsonic then that'd be a nightmare as one doesn't, without masses of measurements, know precisely where the bullet transitioned from each velocity zone and whether the drag is, for instance a v^6 or a v^2 etc.
It'd be a lot of fun to measure it but I think the Artillery types in the 19th / 20th Century produced a lot of paperwork on the subject.
This is exactly what Sierra do. ...the thoroughness of the research Sierra put in. This is incorporated in their Infinity software.