Nosler Accubond LR G1 or G7

[steve-r]

Picked up a new T3 300 WinMag with a brake for my son.
Found some Nosler Accubond Long Range in 190gr and Ive been looking at load data. Never used Nosler AB's before. Also found some H1000 and Federal 215m's, and Hornady brass.
We mounted a Leupold VX3 3.5x10 with a Boone and Crockett reticle so Ive been looking at loads trying to find a muzzle velocity that will produce ballistics as close to the B&C reticle spec as possible for 300, 400, 450, and 500 yards drop, based on 200 yd zero. Calculator suggests 2850ft/sec is the closest match at all ranges.
When I enter the handload data, it is asking me for the ballistic coefficient(BC) for the bullet.
According to Nosler the G1 BC is .640 and the G7 is .325.
The calculator is giving me a very close match to the reticle ballistics using G1, but when I enter the G7, i get way more drop.
Can someone help me understand the difference in Noslers G1 vs G7 spec, and suggest which Ballistic Coefficient spec I should be using?
I should mention we havent fired a shot yet, so will be tweaking the load once we get some actual chrony data
This exercise is for my son to understand the ballistics of his rifle in prep for elk season.
Thanks in advance!

 

[todbartell]

I'd use the Litz BC of .570G1 or .292G7

Somewhere around 2850 fps should jive nicely with the B&C / 200y zero on 10x magnification

On 10x, the subtensions of the B&C are :

2.2moa (first line)
4.8moa (second line)
6.3moa (smaller hash mark)
7.8moa (tip of post)

Using the Gseven ballistic program on Gunwerks website (1.75" sight height, 2400' elevation, 50F temp)
.570G1, 2850 fps
200y zero
300y -2.2moa
400y -4.7moa
460y -6.4moa
510y -7.8moa

Switching to .292G7, 2850 fps
200y zero
300y -2.2moa
400y -4.7moa
460y -7.8moa
510y -11moa

JBM ballistics is another good program. I checked the two programs against each other and the numbers are the same. I prefer the Gseven one as you can create a profile and save different loads etc.


https://www.jbmballistics.com


https://cdnp.leupold.com/products/p...aiming-system-manual.pdf?mtime=20170626163401

 

[stubblejumper]

 

[steve-r]

Thanks both for the BC corrections.
It seems the Nikon SpotOn app is giving me a different result for G1 and G7, and it does allow me to load a G7 profile for the bullet, but its the G7 profile that seems to be incorrect.
We will re-do the exercise using the calculators you suggested TB.
much appreciated!

 

[steve-r]

Update...I went back into the Nikon SpotOn mobile app to try and understand why it was giving me a different G7 result. I found a buried setting allowing selection of either the G1 or G7 drag table...my error was entering the G7 BC but leaving the setting on G1.
Sometimes it just takes input from others to help figure out problems.
Thanks again to TB and StubbleJ, and this forum as a valuable resource!

 

[Dogleg]

Work up your load first, and worry about matchig the B&C second. For starters, it might not shoot so brooding about it before hand might be a waste of brooding time.

Next, I’m curently shooting that bullet in 3 .300 Wins and am getting velocities of 3150, 3150 and 3080. The slow-poke is a 26” factory barrel and the other two are Lilja and Benchmark. The slow one eats an extra grain of H1000.

Next off, the correct drops of your B&C reticle are 2.19, 4.80, 6.26 and 7.82 MOA at the post. With my loads it lines up with a 300 yard zero, 400,500, 600 and its just smidge low at the infinity pin at 650. Nothing that throwing an extra click into the mix wouldn’t cure.

A slightly less enthusiastic one would line up 3,4,5, 550 and 6. Candy-ass loads with welfare bullets will come in a 2,3,4, 450 and 500.

Litz is a smart guy; so when he publishes corrected BCs with no mention of muzzle velocity or the spread it was calculated over he probably has his own reasons. None of those reasons are to help sell Noslers.