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Old 22nd November 2009, 10:48 PM
Weevie Weevie is offline
Join Date: Apr 2009
Location: Worcester
Posts: 254

Originally Posted by rubi-tong View Post
So your saying that there is no difference (neglectable) between 1.5" scope height and 1.8" scope height. I'm trying a Hawke 2-7x32 map6 over the winter, to mainly find out if I can do away with my bracketing and start estimating by eye.
My belief was a lower scope flattens your trajectory out slightly, is this incorrect?
The front of the Rail on the PT is not very deep so i think i may just keep it on ,as taking it off, I'm not going to gain as much as I first thought.
Thanks for the advice guys, keep it coming if you have something to add.
Regards, Mark
Well there is a difference. The aimpoints are higher with a 1.5" scope height but the gap between the various aimpoints (say for example the gap between 13 and 16 yards) is, according to chairgun mobile at least, pretty much the same between the two scope heights.

That is to say, for example, the gap between the aimpoint for 13 yards and 16 yards (with my pellet velocity and BC) is pretty much the same for 1.5" scope height as it is for 1.86".

I guess the effect of scope height on 'flattening' the trajectory at closer distances (at least as far as HFT is concerned) has simply been exaggerated by received wisdom.

I'll check this on Chairgun 2 in a sec (means restarting my PC and booting XP up) and post the results.

Right. Just checked this in Chairgun 2. Here are the results. This is 775 fps with a BC of 0.0210 (see climate change chappies? Sharing your data isn't that hard!)

POI difference between 8 and 12 yards (not such a biggie, mind you, since in UKAHFT at that range the KZ that must be 20mm or greater):

For 1.86" scope height: 0.435" (or 11.04 mm)
For 1.50" scope height: 0.394" (or 10.03 mm)

Aimpoints are 1.1 mm closer together with 1.50" scope height than with 1.86" scope height

POI difference between 13 and 16 yards (more important as this could be a 15mm KZ in UKAHFT):

For 1.86" scope height: 0.236" (or 5.944 mm)
For 1.50" scope height: 0.205" (or 5.207 mm)

Aimpoints are 0.737 mm closer together with 1.50" scope height than with 1.86" scope height

So, a flattening of trajectory of just over three quarters of a millimetre for the really cruicial distances and only just over one millimetre for the less cruicial ones

Even if we go mad and say you can't tell the difference between 17 and 24 yards there's still only a difference of 1.9 mm between the gap between the aimpoints for 17 and 24 yards at each scope height. At those ranges you're aiming in the bottom half of the kill anyway so...

Assuming chairgun's correct (and it tends to be reasonably on with trajectory calculations) there really is no advantage in taking the scope rail off. Just get yourself some low mounts and you'll be fine

Last edited by Weevie; 22nd November 2009 at 11:34 PM.
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