Data not matching shooting

[TheBelly]

My app says 3.6 mils to 500.

what app are you using?

[JustAGuy]

JBM Ballistics: http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi Which gives 2.6 Mils
Shooter Iphone App which gives 2.8 mils
and the Spreadsheet provided by meccastreisand which can be downloaded at http://www.youtube.com/watch?v=RR-1WIvvH1E. This also gives 2.6 mils.

s

[islandermyk]

Parallax.

I've learned (a pretty expensive and hard way) that getting my parallax wrong at 100 yards can and will multiply out to distances, and will throw your whole DOPE off.

That's just me though...

[JustAGuy]

Hmmmmm. Hadn't thought about parallax. I thought I had it pretty well dialed in but I think I'll put more thought into it next time I go.

[islandermyk]

I started with getting a solid 100 yard zero, and remembering everything I did behind the rifle to make those shots...

and parallax use to kick my ass cause I do occasionally get a little complacent.

Your cold bore shot/first shot of the day will let you know if your doing something wrong with the idea that your zero doesn't change.
Figuring that out... then you move out further.

I'm only out to 400 or 500 yards for solid DOPE right now... anything further... I'm SWAG'ng it

[Tim K]

Parallax is a good guess. It would have to far enough off that the image would be pretty fuzzy, but it's very possible. I don't suppose the parallax knob has gone untouched since you shot, has it?

If not parallax, I'm guessing a broken scope.

[eneranch]

Were you dialing in the correction or holding over?? If holding over, was your scope set to the calibrated magnification? Shooting into the wind? 40gr pills fall pretty quick after 300yds and a little wind could make it worse.

[JustAGuy]

No, I adjusted the parallax to get the target as in focus as I could detect with my old eyes. I was dialing in the correction and don't (shouldn't) need to set scope magnification since it's an FFP scope. Wind was about 10 mph at my 300 degree position...so, a quartering headwind. I originally dialed in the 2.6 mils of drop and observed from the hits in the dirt that I was quite a bit low. Then I walked it up using my Mil reticle. Some of the other guys who were watching said they were able to observe the hits in the dust as I walked it up and then stopped seeing hits, indicating that I was probably hitting the steel (lots of shooters so I couldn't hear the hits).

s

[Tim K]

Probably not parallax then. You should have been close enough. I think your scope is at fault. You should need somewhere between 2.5 mils and 3.0 mils to get to 500. Needing double that tells me the reticle is not moving how you think it should be.

Were you shooting prone or off a bench? Bipod or bags? I don't know why I ask, just looking for a clue.

Not meaning to be offensive, but are you an accomplished shooter? I've seen guys at PD matches miss targets by many feet at 300-400 yards due to a lack of experience or skill.

[Tim K]

Just thought of something else. Could be vertical wind. Were these shots in rapid succession or spread out over time? Have you repeated the experiment?