Range Report questionable drop data

[TRG65]

I finally got to try a new 6.5x47 load out at some distance this past weekend and have been trying to fit it to anything I can put in a ballistics program.

My load is
2.68 OAL
139 Scenar moly'ed (pointed with a Whidden die)
40.0 grs H4350
CCI 5.56 primer
predicted velocity from a 24" barrel is 2790 (but I never believe QL predicted and knocked it down to 2750)

Conditions were 30.04" 95F and 80% humidity and about 2700DA at least that would be an average of the couple times I tested with my kestrel.

zero is 100
330 yds 1.1mil put the center of the group about 1" low (5 shot group was about 1.75"
560 yds 3.4mil put the 5 shot group 7" low of the POI (3.5" group)

To get things to come close at the longer range I have to back my G7 from .290 (standard for 139 Scenar) to .270 and the velocity back to 2700, but then the 300 yard is pretty off. I'm using Ballistic FTE.

I have 2 questions.
What would be a reasonable velocity for this load, 2700 just seems too low?
How much would mirage affect the adjustment given that the group wasn't bad just low?

Thanks
Seth

 

[jbailey]

Re: questionable drop data

Well first off, if you are at 30"Hg and 95*F, I'm not sure the DA will be that high... but beyond that...

A straight up 139gr Scenar (no pointing) has G7 BC of 0.285-ish, so I don't think your 0.270 estimate is accurate (that would be down in the 123gr Scenar range).

Moving on to velocity, I come closest to buying your 2700fps estimate. For a 24" barrel, that sounds about right for 40.0gr H4350. However, this MV doesn't make sense with the dope you gave...

Running a 139gr Scenar at 2700fps in 30", 95*, 85% off 100yd zero and a 2.0" above bore scope, JBM predicts 2.8mils to 560, about 0.9mils lower than your real world results. I think you need to get the load on a chrono...