Bullet impact at different distances.

[onelastshot]

Quick question; If your rifle is zeroed at 100 yards (it's a 6.5-284, 140 grain bullet if that matters) where would you expect the bullet impact to be at fifty yards? Half inch low, possibly an inch? Years ago I read somewhere that a bullet would impact at 33 feet (possibly yards) at the same level as 100 yards. Does anyone ever recall reading something of this nature? The reason for the question is I'll be trying to sight in a rifle tomorrow but won't be at my normal 100 yard range; I'll only have about a fifty yard range to work with. Any input would be greatly appreciated.

 

[K22]

There are numerous sources for ballistics data. The one I use is www.federalpreimum.com/ballistic-calculator.

This will give you an approximation of bullet trajectories at various sight in distances for different velocities, bullet styles and bullet BC's.

Keep in mind because of all the variables involved that this is only an estimate. The only way to obtain more precise data is to shoot your rifle with your load. Even then, because of load variables, shooter variability, and environmental conditions there will be some variability in your data, but you will be able to obtain a useful bracket of bullet trajectory.

 

[davidjoe]

Low, by approximately half of the height the crosshairs, over the bore’s center.

 

[Bill Norris]

From the checking I have done with bullet speeds around the 3000 fps range app. 35 yard zero will put it fairly close at 100 yards.

 

[davidjoe]

Quick question; If your rifle is zeroed at 100 yards (it's a 6.5-284, 140 grain bullet if that matters) where would you expect the bullet impact to be at fifty yards? Half inch low, possibly an inch? Years ago I read somewhere that a bullet would impact at 33 feet (possibly yards) at the same level as 100 yards. Does anyone ever recall reading something of this nature? The reason for the question is I'll be trying to sight in a rifle tomorrow but won't be at my normal 100 yard range; I'll only have about a fifty yard range to work with. Any input would be greatly appreciated.

Be careful not to confuse something written about a .22 RF with your CF rifle.

CF’s should come up to line of sight at 100 one time if zeroed at 100, and need come ups beyond 100.

.22 RF’s drops more from the muzzle to 100 than the height of a scope mount.

Therefore, the .22 needs to pierce the scope’s waterline before 100 yards while still rising, and come back down to it at 100.

CF’s like yours don’t drop more than a mounted scope’s height on the way to 100 and therefore shouldn’t be dead on at 100, at different distances, - but, I do mount them high, and that’s my experience.

If you zeroed at 200 with a CF, you’d cross the 100 zero, on the way to 200, touch tangentially at 200, start dropping again and recross the 100 zero once more probably several scores of yards later.

 

[painter]

JBM Calculations will answer this by allowing you to add the information that you need.

 

[davidjoe]

Noodling on this more, I think the principle would be stated this way:

**** All bullets follow a “rainbow” path to hit a target at a certain distance, of which you may choose to zero the scope at.

If the height of the rainbow at that chosen distance is greater than the height of the scope over the bore, then your bullet is going to have to intersect the crosshairs twice.

If the height of the rainbow at that chosen distance is still less than the height of the scope over the bore, then you will be able to adjust the scope to tangentially touch the peak of the rainbow, and the bullet will not cross twice. *****

If this is correct, high mounts may be preferable.

 

[onelastshot]

There are numerous sources for ballistics data. The one I use is www.federalpreimum.com/ballistic-calculator.

This will give you an approximation of bullet trajectories at various sight in distances for different velocities, bullet styles and bullet BC's.

Keep in mind because of all the variables involved that this is only an estimate. The only way to obtain more precise data is to shoot your rifle with your load. Even then, because of load variables, shooter variability, and environmental conditions there will be some variability in your data, but you will be able to obtain a useful bracket of bullet trajectory.

Thank you. The Federal Ballistic calculator is exactly what I needed for an approximate range estimate. Having the bullet impact at .5 inches at 25 yards will have it impact at 1.2 high at 100 yards, 1.2 at 150 yards and point zero at 200 yards. I will check again when I get to my 100 yard range but this will provide an excellent starting point.