Thread: "Trueing" BC/Velocity

Originally Posted by eamars

Your elevation looks fine to me. If you're aiming the center of the plate, your dope seems correct.

I suspect Gimp has adjusted dope to get to where he is and now is asking if he should adjust either BC or Speed to line up

Originally Posted by Gibo

I suspect Gimp has adjusted dope to get to where he is and now is asking if he should adjust either BC or Speed to line up

To be clear, I'm setting up a strawman to test other's thinking, not genuinely asking for advice

Originally Posted by gimp

To be clear, I'm setting up a strawman to test other's thinking, not genuinely asking for advice

Greetings @gimp,
Assuming you have a half decent chronograph I suggest you use your measured velocity. If you want to measure your down range velocity you may want to consider joining your local NRA club so you can use the Silver mountain kit. This will either correct or validate the predicted velocity. If the downrange velocity checks out then any difference in trajectory in likely to be operator error (sorry). If you can't measure down range velocity and wanted to change your predicted trajectory then I would adjust the BC and not the velocity. In spite of what some believe BC varies from shot to shot and day to day. I would also do some test firing at 300 metres to see how trajectory matches prediction. Last as mentioned above a decent aiming mark on you 600 metre target would help.
Regards Grandpamac.

Originally Posted by grandpamac

Greetings @gimp,
Assuming you have a half decent chronograph I suggest you use your measured velocity. If you want to measure your down range velocity you may want to consider joining your local NRA club so you can use the Silver mountain kit. This will either correct or validate the predicted velocity. If the downrange velocity checks out then any difference in trajectory in likely to be operator error (sorry). If you can't measure down range velocity and wanted to change your predicted trajectory then I would adjust the BC and not the velocity. In spite of what some believe BC varies from shot to shot and day to day. I would also do some test firing at 300 metres to see how trajectory matches prediction. Last as mentioned above a decent aiming mark on you 600 metre target would help.
Regards Grandpamac.

I have a magnetospeed v3.

Originally Posted by gimp

I have a magnetospeed v3.

All the more reason not to fiddle with the velocity then.
GPM.

Originally Posted by gimp

I have a magnetospeed v3.

So if you have a 9g bullet with mv about 2500 fps and a 4500g rifle that will Be recoiling backward at about 5 fps by the time the bullet passes the magnetospeed you would need to subtract 5 from the measured velocity ?