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-   -   Scope height over bore (question for long range shooter) (http://www.firearmstalk.com/forums/f48/scope-height-over-bore-question-long-range-shooter-90797/)

Nathantc 05-16-2013 08:09 PM

Scope height over bore (question for long range shooter)
 
ok i been playing with my ballistics computer and it seems that for my .270win its better to have my scope at about 3" than to have it at 1.75" if my only range that i use it for is between 200-400 yards, no closer rarely farther.

according to the computer it will require the lest about of hold over or elevation adjustment when zeroed right at 300 yards

i have always been told the closer to the bore the better but this is disproving that completely
the closer to the bore the bigger the drop from 300-400 yards,, noticeably

higher = less rise at 200 and less drop at 400 with a 300 yard zero
closer = more of both

am i doing some thing wrong or is scope hight really making that big of a difference

also you might note that all of the super long range sniper rifles have the scope pretty far from the bore due to rifle design but could that be a benefit for extreme distance (im not talking about the puny .308 either, im talking about 338 lapua, 408 cheytec, 416 barret, and of course the 50 bmg)

Crazycastor 05-25-2013 01:41 PM

How much does the bullet drop from 300 yards to 400 yards? I think my 30-06 drops 27 inches. Could that be a factor?

Nathantc 05-25-2013 10:51 PM

Quote:

Originally Posted by Crazycastor (Post 1257719)
How much does the bullet drop from 300 yards to 400 yards? I think my 30-06 drops 27 inches. Could that be a factor?

not sure i would have to look again,, but if zeroed at 300 the drop is different with different scope heights over the bore

Txhillbilly 05-26-2013 02:08 AM

On my bolt action rifles,I try to set each one up the same as far as scope height from centerline of the bore. I always zero my rifles at 100 yards,but have set my 300 WM at 200 before,but I shoot at all types of ranges from 50 yards to 1200 yards.
Depending on the style of stock,and size of the scope that will determine the minimum height that you can mount a scope from the bore.You mainly want to be able to have a good cheek weld on the stock,and still be able to look directly through the scope on every shot with the least amount of body movement. If you change it at all,your shots will not stay the same. It doesn't matter whether your 1" from the centerline or 4" from the centerline of the bore,if you are not in the same position every time,you'll be off on your shots.
The ballistics for the bullet will remain the same,but by changing the scope height perimeters on a ballistics calculator,you changing the angle in which the round is seen from your view,and that changes the drop rate for the same distance. When the round is fired,the trajectory of the bullet doesn't change because you mount your scope higher or lower to the bore.

Example- My Savage 12 FLVSS and my RRA 20" varminter have the same 6-24x50 Weaver Classic Extreme scopes on them. The scope on the Savage is lower to the bore than the scope on the AR15,the reason is the stock design. If both rifles fired the same bullet at the same velocity,the one shot out of the Savage would seem to drop more at the same distance because the scope is setting closer to the bore centerline. But in reality,the bullets are doing the same thing,just at different shot angles.

c3shooter 05-26-2013 09:41 AM

There is more to it than simple height of scope- Those rifles with very tall scopes also have a straight line design. Otherwise you are getting a scope mount that will flex more, not having a stock weld to give a reproducable aim shot to shot, etc-

Otherwise we would have 12 inch mounts on all rifles, and be shooting at 3 miles.

bigjim 05-26-2013 02:26 PM

Without information on the scope, I am not sure we can answer. I always thought it was measured from center bore of the barrel to the center of the scopes objective, so a 50 mm would be different than a 40 mm objective. The other factor is your cheek weld on the stock and being able to see down the scope correctly without having the rifle floating in the air unsupported.

Jim

Nathantc 05-26-2013 04:38 PM

not talking cheek weld at all,, im just saying i have noticed that it will change your drop values with different scope heights,,,

regardless of the scope itself,,,

Txhillbilly 05-26-2013 11:27 PM

Quote:

Originally Posted by Nathantc (Post 1258595)
not talking cheek weld at all,, im just saying i have noticed that it will change your drop values with different scope heights,,,

regardless of the scope itself,,,

And it doesn't matter at all,if you don't have a good cheek weld on your rifle if the scope is mounted 3"-4"-6" or a foot off the bore centerline. You won't be able to hit $hit with the rifle.
No matter how high or low the scope sits on a rifle,it doesn't change the ballistics of any bullet. It just changes the ballistic perimeter because the scope to bore centerline has changed.

I don't know what you're trying to accomplish.If you are only planning on shooting out to 400 yards even most cheap scopes have enough adjustment range to shoot that far.

Nathantc 05-26-2013 11:58 PM

i understand and know this

but i was just playing with a ballistics computer and noticed that with certain scope heights it will make it seem to shoot flatter at different ranges,,, im not fool and i know that it doesn't change the bullet path, just the straight line of sight angle threw the bullets arch... just wondering if anyone has tried to use this to some advantage

bigjim 05-27-2013 06:41 AM

Quote:

just wondering if anyone has tried to use this to some advantage
NO, just comfortably mount it so you can see what you are shooting at. And that the front objective is 1/4 to 1/2 inch off the barrel. And that the bolt does not hit the scope when you open the breach.

Jim


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