Range Report Federal GM 175 SMK - Dope Help

[Hoyt7mm]

I ran into a problem a couple of weeks ago when doping my 308 and checking data with the Federal GM 175 SMKs. The punch line is I can't seem to get my AB program to line up with my real world dope. Hoping you guys can find my error, or provide some insight.

We used 1" waterlines on all targets when verifying dope.
Rifle shot/shoots extremely well with this ammo (1/2 moa at 500)

Rifle Details:
308 Win - 1:10 RH 5R
2675 fps (checked same day, with same lot of ammo using both LabRadar and Magnetospeed)
100 yard zero (check same day, with same lot of ammo)
2" Scope Height
44 deg F
725' elevation
29.75 Pressure
72% humidity

Actual Dope (Ranges confirmed with Sig Kilo 2200 and Leupold 1800):
223 yds - .9 mils
325 - 1.9
476 - 3.4
526 - 3.9
825 - 8.0
905 - 9.4
Conditions that day were mild...little mirage, less than 5 mph R->L wind, and overcast

I've played with MV, BC, zero offset and can't find any combo to line up. Also ran a tracking test, and the scope passed without an issue.

 

[Eric32]

Your zero offset should be -.2 mils according to Strelok and all the numbers line up

Correction your 800 and 905 lines up but your closer 476 and 526 are off by .2 but your 223 and 325 line up

 

[davsco]

what is ab telling you for those distances, what bc's are you using for what speed bands?

you sure on that fps, i'm at 2592 out of a 24" barrel, you're almost 100fps more.

also double check the 2" scope height, center of bore to centerline of scope.

 

[Hoyt7mm]

Odd that Strelok seems to be that much closer. I may have to give that a shot.

I'm sure on the MV. 26" barrel...reamer was designed specifically for the GM 175s. My partner and I both took notes and pictures from LabRadar and Magneto. It's not a dyslexia moment for me this time.

I'll double check scope height, but I'm almost positive it's on. Less than .1" off if it isn't.

BC used is .243 G7. No velocity bands or anything fancy. I spent near an hour playing with MV and BC by up to 10% from noted and wasn't able to get it to line up.

Side note - I don't think it is range/conditions related since we had multiple rifles out that day and this is the only 1 that exhibited issues. It also showed the same issues from ~11AM to 4PM.

 

[Eric32]

So I used .243 G7 and your MV of 2675.

But i added .2 mil offset. But can you verify your distance on the range using a GPS or google maps imagery.

 

[davsco]

here are the g1 numbers per sierra's website. throwing these in vs a single number helped me get theory closer to dope. maybe there are some g7 numbers floating around also.
.505 @ 2800 fps and above
.496 between 2800 and 1800 fps
.485 @ 1800 fps and below