stubblejumper

I am having a hard time convincing an individual that in order to use a ballistics calculation,you must know the sight height.He insists that if you know where the point of impact is at 50 yards,you can use the calculation to find the point of impact at another rangewithout knowing the sight height.He claims that different heights of rings will not effect the results.Your opinions on this?

longrifle1000

The ballistic program I use takes sight height into account. I would venture to say that it is a neccessary component to calculation of trajectories.

bigcountry

My opinion is to send the young boy to a good geometry class. And buy his books and teach him something.I can't believe all the folks who take these calculators so serious without trying them out. I have seen shooting past 500 yards where .1" makes a world of difference.

I use sight height as like "k" value. Math guys know what I am saying. Bascially use the calculator to get you on the paper at 500 yards and then take your velocity, BC, and altitude, and spit that into your bullistic calcutor and play around with sight height until you match up your real time results with the calulator.

James B

I can only say that I have high rings, low rings and medium rings. Once sighted in, I have never had a problem with dialing in at any range. This from shooting the 500 Meter steel silhouettes with several different rifles and scopes. Maybe I am misunderstanding your point.

pig dog 02

I asked a question about this in a recent thread. I fully trust and believe that scope height does affect MPBR...but my question is how? I would like to understand how. I have a hard time grasping the idea that the height of a scope above the boreinfluencesthe arc pathof the bullet.

If anyone can explain how this happens, I would be grateful. I prefer to know how it works rather than just plug numbers into a formula and see the results change.

Thanks,
PigDog

stubblejumper

Judging by your answer ,you certainly are.
The question is,when using trajectory calculations,do you have to know the height of the sights or crosshairs above the bore to use the calculations?If you use a trajectory calculator,does it ask for sight height?Why?

Anthony T.

Sight height most definetly affect MPBR. It's just a scientific fact. Do a google search and hand him your laptop. He'll see. It's really a no brainer though. [&:]

doubleA

Yes the sight height above the bore has to be taken into account. The down range trajectory or path of your bullet changes slighty with changes in the height of the scope/sight. Unless your are shooting tiny targets at long ranges in my opinion it's a moot thing.

For what it's worth I just ran these figures using a 7mm Nosler BT driven to 3450fps at ranges out to 1000 yds with sights 1 inch, 1 1/2 inch and 2 inches above the bore.



At 1000 yards the difference is only appx 9 inches with a 1 inch difference in sight height.

Of course with all computer ballistic programs I only use them as a guide, in actual shooting at these ranges the results will vary.

Pig Dog.... the bullet, no matter how fast it's drivenwhen fired from a firearm travels in an arch. Now imagine your eye sight is as staight line. When you are looking through a scope this imaginary straight line intersects the arch(path of bullet) twice. When you raise and lower the imaginary line(line of sight) through the arch it does change the amount ofelevation of the bullet at various distances. It's kind of hard for me to explain but in reality is quite simple.

m.t.hands

show him a gross over exgeration(sp) of iron sights, say like some five inch tall ones, then explain line of sight and bullet path travel/traj.

i had a budy of mine swear that "bullets rise" because of air when they leave the muzzle, i used the big sights and line of sight to finally get him to understand that the two points meet/intersect twice....

hope this help, cause i understand what your dealing with

pig dog 02

I think stubblejumper and I have come to the correct conclusion. Scope height does not change the arc path of your bullet. Think about it...how could a scope change the way your bullet flies?

What actually happens is a change in perspective. When your scope height changes, the angle of your line of sight changes. So, with different scope heights, your LOS intersects bullet arc at different points in space. I used this example in a different thread:
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"I am visualizing a line of sight (which is straight) and a bullet path (which is an arc). For simplicity, lets say the arc crosses the line of sight at 50 and 150 yds. And it reaches the peak at 100 yds...3 in. above line of sight. And it reaches 3 in. below line of sight at 200 yds. That means the Max Point Blank Range is 200 yds with the scope zeroed at 50 and 150.

Ok, so now we raise the scope higher and angle it down, forcing the same 50 yd intersection of LOS and bullet arc. The second intersection would be beyond the original 150 yds...lets say its at 175. But in this case, the peak of the arc would be more than 3 inches above LOS. So, I can see now that you can't just say, "if I am zeroed at 50 then i am 3 inches high at 100" (for this example)...because your scope height may or may not allow for the correct LOS angle to make that true. But scope height will not infact change the MPBR. The LOS angledoes not affect actual arc path/shape.

So, scope height will affect POI, but it will not affect MPBR. Right?

So, the next question is...knowing the arc path of the bullet, how do you figure out proper scope height to get the most out of thearc? In other words how do I know where my LOS shouldbe in order to make the arc's peak 3 inches above it? "
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Anyways, your actual bullet arc does not change with scope height, but your LOS angle does change, which affects point of impact, and perceived bullet path. Ultimately at ranges under 300 yds, it probably makes very little difference.