Trued 3 bullets today

[pitdog85]

Just looking for some thoughts. Took 3 bullets out to 800 metres today to true them up. Was a perfect day for it with light rain most of the time which kept mirage to a minimum.

I shoot with the magneto on all the time today was no different. First bullet was the 123 lapua scenar. Ballistic ae was calling for 23.3 moa up. Actual centre line hits came in at 25.25-25 Moa at average velocity of 2821. This trued up to a G7 of .235 vs lapuas advertise .263 how does this sound to others.

Second bullet was Berger 130 vld they averaged 2784 ballistic ae called for 22.9moa actual around 24 Moa trued G7 bc of .270 vs Bergers advertised .288

Last bullet was the ever reliable 139 scenar. With this bullet I used both ballistic ae and hornady 4dof with 4dof being more accurate. Velocity of 2678. However it also trued up at .270 G7 va .290 as per lapua.

I have a feeling I'm getting slightly less bc as my velocity is probably a bit less than what they were tested at. Sierra gives the velocity bands unfortunately lapua and Berger don't.

The only other possible issue is I zero'd my scope 2 weeks ago at sea level and this was shot at 390metres above sea level. This shouldnt make a difference but I'm not 100% sure on that. Will retest zero.

I have tall target tested scope but as per previous thread this is too unreliable in my view to do with any repeatable and consistently that I would be happy with so just leaving that as 0.

Anyway I mainly wanted to see if these trued up bc seem resonable based on my velocities as I havent seen many others post what sorta changes in actual bc they have made to true up. I know frank was talking about his 136 scenars on the podcast and how they trued up to much higher than lapuas advertised as he was running them fast.

Thanks

 

[Mordamer]

In my opinion your distance is not far enough to do a very good job of truing up a BC. If your zero was off by 1/2 MOA or your velocity readings are off by 20 FPS you will get a pretty far off BC from the manufacturers. The fact that you had to true all bullets BC's down by about the same margin is a hint that there might be some other error in your setup. Scope tracking being off by 2 clicks at that distance could cause this also. Anyways, if you are getting solid hits at all distances from 800 meters in then carry on.

 

[bschneiderheinze]

There’s so many variables to check I switched scopes and didn’t check my bore to center height afterwards it went from 1.8-2.0. This made a drastic change in my dope and explained why I had been shooting high by around .2 mils 500 and beyond. Barometric pressure changes can make a much bigger impact than elevation if you didn’t check them.

 

[pitdog85]

Thanks guys I check weather with my kestrel around every hour so I know that's good. My zero height is good as well.

I think Mordamer is on the money with either my zero off or scope off. I don't think it's velocity as my magneto seems to always be reliable and I mount it the same way everytime.

One other thing I didn't mention is when I zero my rifle I use
My atlas bipod with legs straight up and down. When I shoot out to 800m due to the logistics of my shooting location I have to use the atlas with legs 45 degrees forward. Would this potentially cause a point of impact shift? All shooting is prone?