Prime 6.5 Creedmoor published BC vs actual BC

RoterJager

The Red Hunter
Oct 21, 2013
578
101
43
The Frozen Tundra
#1
I went out today to true up my Kestrel with what I'm seeing in real life. Unfortunately I only have a 567 yard range to true things up on at the moment so I have to make do with what I have. I'd have like to run out in 100 yard increments however the 200-400 lane was being occupied by people doing mag dumps on their ARs for well over an hour. I'll have to get out and go from 200-567 in 100 yard increments another day.

The published G7 BC for the Prime Norma 130 Diamond is 0.295. With that BC and my environmentals for today, my Kestrel was showing 2.66 Mils of elevation and anywhere from 0.05 Mils to 0.2 Mils for wind holds. My actual elevation is 2.5 Mils. I have to adjust my G7 to .360 to get things to line up with what I'm seeing in real life. Has anyone else seen this discrepancy in the published BC versus the actual BC on Prime?

Firearm:
AI AXMC
26" AINA 6.5 Creedmoor barrel
TBAC Ultra 7
NF ATACR 7-35x56 Mil-C
Round count: 140

Ammo:
Prime 6.5 Creedmoor
Velocity: 2948fps avg.

Environmentals:
Temp: 75.2 F
Station Pressure: 29.20
Humidity: 49%
DA: 2050


Maybe @Lowlight or someone else that shooting Prime more often than I can chime in with some insight?
 

Lowlight

HMFIC of this Shit
Staff member
Apr 12, 2001
27,025
2,550
113
Base of the Rockies
www.snipershide.com
#5
With that software you adjust either MV or BC, I have found adjusting the BC is better, although your range is a bit short, anything will work you are not shooting far enough to matter.

Being off .1 Mil at 600 is only 2" off, I am sure you are not holding a 2" group at 600 yards, so let's say you shoot 1/2 MOA that is 3" you are inside the group size, in other words, you are splitting hairs on both range and elevation.

Using AB with my 136gr load when I did the BC at 800 yards it was listed as .545 and I ended up using .588 to line it up. Fixed a lot of shortcomings from the software by using a better BC vs changing the MV by 100fps
 

RoterJager

The Red Hunter
Oct 21, 2013
578
101
43
The Frozen Tundra
#6
With that software you adjust either MV or BC, I have found adjusting the BC is better, although your range is a bit short, anything will work you are not shooting far enough to matter.

Being off .1 Mil at 600 is only 2" off, I am sure you are not holding a 2" group at 600 yards, so let's say you shoot 1/2 MOA that is 3" you are inside the group size, in other words, you are splitting hairs on both range and elevation.

Using AB with my 136gr load when I did the BC at 800 yards it was listed as .545 and I ended up using .588 to line it up. Fixed a lot of shortcomings from the software by using a better BC vs changing the MV by 100fps
I did make it a point to avoid touching my MV in the Kestrel. No point in having a Magnetospeed if I'm not going to trust what it's telling me.
 

Lowlight

HMFIC of this Shit
Staff member
Apr 12, 2001
27,025
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113
Base of the Rockies
www.snipershide.com
#7
That has always been my issue too

We have much better Chronographs that guys are buying, then their "App" asks them to change the MV by a wide margin, so the question becomes, what is the point of even owning a Chronograph is you are just gonna change it. Between LabRadar and MagnetoSpeed why are we changing these numbers so significantly?

Might as well SWAG it regarding your MV, figure out the drop and then true the software and let it pick a new MV for you. it's gonna ask for that anyway.
 
Jun 26, 2012
2,653
1,346
113
N. Carolina
#8
I did make it a point to avoid touching my MV in the Kestrel. No point in having a Magnetospeed if I'm not going to trust what it's telling me.
at some point you will have to adjust both. what lowlight is saying do the BC first and then maybe a slight tweak of the MV to bring it in line, ive never done more than half of my ES (which about covers the margin of error in the chrono...i use a MS and Labradar).
 
Feb 13, 2017
85
13
8
39
Ohio
#9
Not to hijack the thread, but I can only find the 130 diamond bullet with Molly, I cand find the 130 golden target, how does it compare to the diamond?
 

bohem

PVA's HMFIC
Jan 6, 2009
7,231
641
113
Southeast, PA
www.patriotvalleyarms.com
#10
The distance being used is too short like Frank said.
I've shot the stuff using the published BC at 2920fps and the numbers were dead on from point blank to 1100yd.
I built a rifle for Jim O. last year and he called me to tell me that the rifle was dead nuts, 1st round hits the first day at the range from a 100yd zero all the way to the max distance they had, just inside 1000 yards.

At short range you can have surprisingly large differences in the BC input with very little change in impact location. Between this and the granularity that comes in the scope turrets (0.1mrad isn't all that small in cases like this) then you can have a situation like you're describing.

Also, something that's come up in the past is mirage. A rising heat on the range you're shooting will make it appear to throw the impacts off substantially. I've seen it be 0.3mils or more at ranges when we shot on a range where most of it was brown dirt, then you go over to a lane that's mostly in the shade with grass underneath and the trajectory is over the target. It had nothing to do with the trajectory and everything to do wtih the mirage making the shooter THINK they were holding on the target but inreality they were holding over by several tenths.
 

Lowlight

HMFIC of this Shit
Staff member
Apr 12, 2001
27,025
2,550
113
Base of the Rockies
www.snipershide.com
#11
I was setting up two rifles this past week with AB and using Prime Ammo

I tweaked the BC a bit, up, because I was shooting faster, and then it only changed my MV by 23fps to line up.

Adjusting the BC at distance for your rifle is the best plan when using software that can only tweak one or the other
 

FishDr

Sergeant of the Hide
Apr 10, 2014
326
20
18
southern IL
#12
Not to hijack the thread, but I can only find the 130 diamond bullet with Molly, I cand find the 130 golden target, how does it compare to the diamond?
I dont believe the coating will make a difference. I use a G1 of .585 with good success to just past 1k. Hope this is helpful.
 

stevenc23

Full Member
Oct 21, 2013
709
34
28
#13
Also are you sure that your 100 yard zero is true? When checking dope it is nice to be able to go between 100 (or whatever your zero distance is) and then to your long target to confirm it is not just your zero being off a little.
 
Feb 13, 2017
85
13
8
39
Ohio
#14
I dont believe the coating will make a difference. I use a G1 of .585 with good success to just past 1k. Hope this is helpful.
Thanks for your reply.
I was actually looking for bullets to reload. I can’t find any that’s not Molly coated. I know this doesn’t pertain to the topic, but I thought I would ask here because of the topic, if that makes sense. Lol
 
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