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Drumsnguns

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Jun 14, 2016
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North Carolina, United States
I'm using Strelok Pro with with Zan Slugs and an Impact MK2 with the Heavy Slug Liner with a 1:18 twist rate. The projectiles are .25 Zan 37 grain. It's zero'd at 50 yards.
Projectile weight: 37.05 grain
Projectile speed: 985 fps set to measured temp and humidity (Metro)
BC 0.108
Target distance: 120 yd
Scope height: 8.0 cm (first focal plane)

Angle is minimal

The app says at 120 yd, the elevation should be 2.7 MRAD but in order to get on target, I'm having to set things to 3.4.
With NSA slugs it was very close to what the app called for. Having much better luck with ZAN.
So it's a riddle....what do you think I might be doing wrong?

Note: the scope is on FX elevator rings; perhaps that's messing with things?

Thanks for the help.
K
 
As long as you remeasured the center of scope to center of bore using the FX elevator rings, you should be okay. As long as nothing else was changed.
Did you change moderator perhaps? A heavier mod will make that kind of difference.
The slug weights are exactly the same between NSA and Zan?
Just throwing stuff out there to possibly help.

Mike
 
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I am finding that most published BC's are for comparison only by one source using the same gun, like what HAM does. My results are usually different. I use Strelok and change my inputted BC until the app matches the actual trajectory of the rounds I'm shooting. You need a calm day and an accurate gun to do this quickly or you have to check it over several outings and average it. Basically what you and Tumblinginflight just did. Every time.
 
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Airgun BCs are only valid for a specific distance. I’ve tested a number of pellets and slugs and the BC usually varies depending on the distance I measure it to. Since BC tends to be highest up close that’s what is usually reported.

Plus there are test conditions (altitude, temperature) and the ballistic stability of the slug or pellet in that gun with its current tune.

Bottom line: believe your testing. Only use the app for intermediate elevation calcs after you’ve tuned your ballistic software to match your real world testing.
 
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Also put in the correct altitude or better yet the actual station pressure at location.

Make sure elevation correction factor is at 1 as well(this is scope click value in case it doesn't track correctly). Check if Zero range is correct(sometimes I switch between a 25Y zero and a 50Y zero but forget to change it in the app), That Zero height is at 0.0, and Zero offset is at 0.0.

Furthermore stated BC's can be off and crappy chronos can be off too.
 
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steve123 said:
Also put in the correct altitude or better yet the actual station pressure at location.

Make sure elevation correction factor is at 1 as well(this is scope click value in case it doesn't track correctly). Check if Zero range is correct(sometimes I switch between a 25Y zero and a 50Y zero but forget to change it in the app), That Zero height is at 0.0, and Zero offset is at 0.0.

Furthermore stated BC's can be off and crappy chronos can be off too.
Click to expand...
I did wonder about the accuracy of my range finder. Wish I had a second chronograph.Thanks for the input.
 
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