Adjusting BC for ballistics?

LennyITI

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My press for my own reloads has not arrived I just bought some factory loads. I am using a Labradar and the box of Peterson loads stated 350gr Sierra Matchking with a G1 0.805 at 3280 FPS. I was getting 3158 Ave with my rifle. When I enter the info into my keastral and my other ballistic app my point of impact is lower. to get it on I had to lower the bc to 0.690 and that seem to make it on at 600 and 830 yards. Is that the better way to correct rather than lowering the fps? I would assume the Labradar is accurritt.
 

L.Sherm

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Having to drop the B.C that far makes me think something else isnt right.
 

Mikecr

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If you're on at 600 and 830 with the adjustment, then you made a good choice.
Now to solve the puzzle about lower than expected G1 BC...

Don't ever lie to ballistic software, or in any other matter in life. It never solves anything.
 

Plinker147

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Use G7 BC more accurate at long distance for VLD style bullets. That’s a lot to have to adjust in BC, but if it works it works
 

LennyITI

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since I bought the labradar it has been very spot on with the ballistic apps, but they were all using batch of 6.6 berger vlds, This is first time I have ever used the sierra bullets let alone a factory load I didnt know ifbc is factored in at certain speeds or not. but I trust my labradar more than the bc. Iam gonna shoot more longer targets this weekend and figured that will be the tell all. Untill this gun all I was messing with was creedmoor and 6.5 PRC using the same batch of bullets I bought 8 years ago. trying to learn the curve on this one might be a little more than my others.this thing shoots better better groups at 800 yards than 100 so my zero sight-in was not as tight as I am use to, but I was 1/2 moa at 830
 

Mikecr

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Could it be an atmospheric setting in the software?
You have not forced any kind of altitude in it have you?
Hopefully just letting Kestrel meter read and calc local air density.

Is LabRadar feeding velocities to meter, or are you manually entering this?
 

LennyITI

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Could it be an atmospheric setting in the software?
You have not forced any kind of altitude in it have you?
Hopefully just letting Kestrel meter read and calc local air density.

Is LabRadar feeding velocities to meter, or are you manually entering this?
Manual enter velocity. Letting keastral take it own reading
 

Jeffrey Van Zandt

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My press for my own reloads has not arrived I just bought some factory loads. I am using a Labradar and the box of Peterson loads stated 350gr Sierra Matchking with a G1 0.805 at 3280 FPS. I was getting 3158 Ave with my rifle. When I enter the info into my keastral and my other ballistic app my point of impact is lower. to get it on I had to lower the bc to 0.690 and that seem to make it on at 600 and 830 yards. Is that the better way to correct rather than lowering the fps? I would assume the Labradar is accurritt.
 

Mikecr

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Anytime someone suggests lying to software, like putting in wrong velocities, -they're lost.
Lenny, have you tested/verified scope click value?
 

Greyfox

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For corrections below 700 yards I wil generally correct with velocity. If Above 700 yards I will consider changes adjusting BC.
 

J E Custom

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Shooting many different brands of bullets, I have never found the published BC's to be spot on with any brand and found that the drop chart best decided what the BC's were in my rifle. I live at 18 ft above sea level and realize that this has a bearing on the ballistics so I test the drop against the velocity at different distances. Most bullet manufactures calculate the BC with ideal conditions, (Low humidity, higher altitude and at ambient temperatures) so unless your hunting conditions can closely match theirs, The BC's will probably not match.

Once the TRUE ballistics of a bullet in your rifle are found the software is very accurate.

Interestingly enough, I have never found BC's to exceed the the advertised BC but again this could be the conditions that I mostly hunt in.

J E CUSTOM
 

dfanonymous

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True velocity in supersonic. True BC in trans and sub. It’s not about if the Labrador is right or wrong. It’s about aligning the numbers. There’s various reasons for this, a lot of it has to do with including human error into the number. Which I’m assuming is the case since bullets don’t group better at 800y then at the 100. Even if one tried to blame it on a stability issue, it’s illogical to think that a bullet would be erratic at 100 then course correct itself at 800 perfectly.

The BC shouldn’t be that low and when you go to shoot further, or even maybe closer, it will be off. Further more, the relevance of BC, to include g1vs g7 vs CC is for the most part (assuming you’re using manufacture recommendations) isn’t worth arguing about until you reach trans and sub. This is where you start seeing significant differences in data. If you’re firing anything past a .5 BC at 3000 fps you’re not even close to to trans at 800. Even if you’re at sea level in a Chicago blizzard.
 

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