Follow my 7 dumbo project aka 7 dasher!!

[4O6shootist]

As @Maurygold and @45-90 said, BC changes as velo changes, also I believe pressure / humidity change it a bit too (someone please correct me on that if I'm incorrect).

In a perfect world, BC on box would be spot on, however you trued your data, which is awesome.

I also noticed your 1000yd group is better than your 605yd group. People group better at distance because the proj has to "go to sleep".

*snigger*.

I eagerly await my internet fight..

If it ain't sleeping at 600, it won't be at a G!

 

[45-90]

Since I have the 6 Dasher with hybrid cases I mocked up some with the 7 mm dasher and 180 gr Berger bullets, I have on hand.

It appears the loads you have are already over pressure for brass cases.

I ran the hybrid cases to 65,000 psi.
Most loads with the 180 gr Berger at 2.620" COAL will reach 2500 fps plus in a 30" barrel.

RL 17 will reach 2600 fps...with hybrid cases...according to QL.
It's a big chore for such a small case.
The 166 gr Atip might be the best bet.

 

[Cz455guru]

All good stuff and thoughts guys, I have gotten to the point that I dont ever trust box bc values but generally they are closer then im experiencing with this project. So that would point me towards something going on with the lower velocity. I was under the impression that hornady 4dof and ab cdm calculated in the muzzle velocity bc variation but I could be wrong on that, either way they have similar drop numbers to what published bc was. Ab cdm was the closest but still .3 off.
Like has been stated i bet a 7.5 twist would help. Mine is a 8 twist.