Re: scope height/ trajectory puzzle

20 September 2004, 06:53

3584ELK

Gee thanks, Louis. How can I ever re-pay you? LOL!

21 September 2004, 07:51

3584ELK

Ed,

Yes, it certainly is a puzzle. Right now the stock is being stained/ finished, so I have to wait for more testing. The only thing that occurs to me is that I tested it for velocity without the cloud covers installed on my chrono. I always thought that as long as the skyscreens picked up the bullet' passage, and you got a believable reading- all was good.

The bench technique was as repeatable as possible, and this rifle was shot on the same day, same range, same spot, as three other rifles. It sure will be good to discover the anomaly.

21 September 2004, 07:17

eshell

Quote:

Bore sight compared to scope sight over varied ranges, using LED type light sources, two, spaced in relation to each other at the muzzle, maybe. I honestly never had to chase this one down, maybe a good gunsmith.

Good luck!

I certainly have a lot to learn, but I don't think this is a concern.

Commercial scope bases are available with 20 MOA or more elevation "error" induced, that allow a centered reticle to be zeroed at 1,000 yards or more. These bases are intentionally "off" and work fine.

IMO, parallel axes are not a factor if the scope will zero. A scope tube that is not parallel will call for more adjustment to get zeroed, often coming close to bottoming out the adjustment, but once zeroed, should be fine as trajectory is concerned. Might not be most desirable for best scope accuracy/reliability, but that's not the issue.

If the scope is mounted "parallel enough" to zero, and the line of sight-over-bore is measured correctly, I see no correlation.

If the velocity is verified, if the other parameters needed for calculation of trajectory are correct, perhaps it is a ballistic coefficient problem.

Perhaps it's external to the rifle.

I suppose there is no difference in bench technique between 100 and 250 that might cause an impact shift? Changing rests or shooting direction might change POI.

No odd wind condition that might drive the bullet downward at extended ranges? Some ranges have documented interference from "humps" that cause odd elevation effects.

Odd problem, for sure. Be interesting to get to the bottom of it.