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Dope help

BrandonK

18" ar15 at 300yds shooting Hornady 68gr. hpbt around 2800 on my crono at 10'ish in front of barrel. 100 yd zero. Scope is Leupold vxr patrol. calc said 1.2mils for 300, I ended up needing 2.2+ any ideas? I entered everything correct to the day and situation as accurately as I could, no kestrel/weather station. Using cell phone weather app. Is the crono off? Could a couple degrees of temp or barometric pressure make that big a difference? It just seemed like a LOT to be off. Any ideas would be nice. Right now I'm kinda looking at it like it is what it is and just go with it. I'm gonna do a tall target test this weekend to check click value. Not sure what else to do?
 
My money's on the chrono giving incorrect velocity but it could be a combination of factors used in ballistic software.
What app are you using?
 
BrandonK said:
18" ar15 at 300yds shooting Hornady 68gr. hpbt around 2800 on my crono at 10'ish in front of barrel. 100 yd zero. Scope is Leupold vxr patrol. calc said 1.2mils for 300, I ended up needing 2.2+ any ideas? I entered everything correct to the day and situation as accurately as I could, no kestrel/weather station. Using cell phone weather app. Is the crono off? Could a couple degrees of temp or barometric pressure make that big a difference? It just seemed like a LOT to be off. Any ideas would be nice. Right now I'm kinda looking at it like it is what it is and just go with it. I'm gonna do a tall target test this weekend to check click value. Not sure what else to do?
Click to expand...
What is your scope height? I think that will make a difference in the app.
 
Hi David, scope height is 2.5" and looking at my enteries I think I put it in at 1.5" I'll have to rerun it. I'm curious to see if that's it. Good call, thanks.
 
BrandonK said:
Hi David, scope height is 2.5" and looking at my enteries I think I put it in at 1.5" I'll have to rerun it. I'm curious to see if that's it. Good call, thanks.
Click to expand...
I tried to run your numbers in my app and with 2.5 scope i got 1.1 mils needed so that may not actually be the issue.
 
BrandonK said:
18" ar15 at 300yds shooting Hornady 68gr. hpbt around 2800 on my crono at 10'ish in front of barrel. 100 yd zero. Scope is Leupold vxr patrol. calc said 1.2mils for 300, I ended up needing 2.2+ any ideas? I entered everything correct to the day and situation as accurately as I could, no kestrel/weather station. Using cell phone weather app. Is the crono off? Could a couple degrees of temp or barometric pressure make that big a difference? It just seemed like a LOT to be off. Any ideas would be nice. Right now I'm kinda looking at it like it is what it is and just go with it. I'm gonna do a tall target test this weekend to check click value. Not sure what else to do?
Click to expand...

+1 0n crono being off. I would zero at 100 yds and shoot a group at 300 and back figure for velocity based on drop at 300 yds . Effectively taking the crono out of the mix. Good luck and let us know how it goes.;)

Regards, Paul

www.boltfluting.com
 
Over 2 mils is a lot for 300yd. The velocity would need to be pushing 2000fps to get that, which sounds unlikely. Since you used BP from a weather station, be sure that is the option used in the app and not station pressure. But that is not enough to cause your issue either. Likely something is off with the scope or mounts. Do you have a mil reticle you can use to compare vs dialing?
 
CharlieNC said:
Over 2 mils is a lot for 300yd. The velocity would need to be pushing 2000fps to get that, which sounds unlikely. Since you used BP from a weather station, be sure that is the option used in the app and not station pressure. But that is not enough to cause your issue either. Likely something is off with the scope or mounts. Do you have a mil reticle you can use to compare vs dialing?
Click to expand...
It is I mil reticle. I'm hoping to get to the range tomorrow and see what's goin on.
 
Above all the electronic data your target is telling the truth. That is why we fire at different ranges and take notes on the results. We place the actual results in the dope - not the ballistic predictions from the software.
 
Ya, I understand that. I was just looking for a possible explanation of why the prediction would be so far off when in other instances it wasn't. Anyway, I did a turret tracking/value test and it was "okay" it was .1 to .2 mils off in height over the 5 available mils I have. Windage wasn't as bad, it did return to zero well. All things considered I guess it could be better/worse. It works for what I'm doing but all things considered I wouldn't buy this scope again.thanks for all the responses guys.
 
I read a post a while back where a guy was having a very similar problem.

It ended up being the way his rings were positioned on his rail. He didn't go into specifics but i think his scope may have been in a bind.
 
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