Observed ballistic coefficient of 123 AMAX

[calshipbuilder]

Figured out my error at 300 yards, I had the ballistics software set for a 50 yard zero while my rifle had a 100 yard zero. :-/

On to better things, I made a graph showing yards to drop. I'm not sure there is a way to get a BC out of the formula (I don't math) but if anyone knows, I'd appreciate the help.

y = 4E-05x2 + 0.006x - 1.0276

As a side note, when I shot these to 1260 yards a while back, they keyholed. Anyone know if there is a transonic stable 6.5 bullet in the 110-130gr range?

[frank]

Are you sure that it was keyholing at 1260 and not just tearing through the paper at an extreme downward angle? The bullet is pretty much dropping out of the sky at that distance.

[calshipbuilder]

Im sure, the bullets impacted at 45deg and all sorts of wierd angles. I'm annoyed I did not take a pic. It took a long time to get on target, I'll try again someday. Fwiw, my dad's 25-06 had the same issues with 115 gr winchester CT.

[bigbear_98]

I know I dug deep but I just found this thread.

So If the "German Guy" was saying the Amax was .218 G7 my idea of the SST G7 being .213 isn't that far fetched.

Also noticed Bryan Litz's new book Ballistic Performance of Rifle Bullets was coming out soon and has the Hornady 123 SST in it.

[Nukes]

Interesting to see the range of BC's that folks are using. In the Kestrel AB we use a G7 of .255 for the 123gn AMAX, chrono at mean MV of 2523fps. We were about a mil high at 1,000 to 1,200 yds until I measured scope height. That correction fixed most of the disparity, now typically 0.2 mil beyond 500 yds.

[lrgrendel]

My results from yesterday

Not sure if you still need any info on the 123 AMAX but these are my results from yesterday

I ran 2 calculations on JBM. 2655 FPS which was the average from my chrono a few weeks ago and 2600 which I used yesterday as the chrono usually is a little faster than actual. As you can see the 2600 was almost spot on.

It is a 1/9 twist and the wind was 10 to 15 k almost from 90 deg and towards the end of the day switched to a direct head wind.

Didn't quite have time to get data at 1000 because it was getting dark.

All the "elevations" were spot on and had a friend spotting with a scope.

Notice the difference between 2655 and 2600 at 1000 yds is 0.5 mil (18")!!

You can read the actual results at 400, 500, 600 and 800 yds from the photos.


Hope this helps

[LRRPF52]

So you didn't need as much drop as it calculated, using the .510 BC G1 drag model, it appears, for the 2600fps mv.

[waveslayer]

I would love to see the G7 BC for the Amax once Litz's book is published. I have had great results on my Shooter app using the G1 BC, that was only at 600 yards. Past that I know it will be way off since the G7 should be used for this bullet and not the G1. Does anyone know the Form Factor for the 123 Amax so we can figure out the real G7?

[Sniper338]

Yes use the g7 bc...

ive noticed similar results to get my data right.

[bigbear_98]

I would love to see the G7 BC for the Amax once Litz's book is published. I have had great results on my Shooter app using the G1 BC, that was only at 600 yards. Past that I know it will be way off since the G7 should be used for this bullet and not the G1. Does anyone know the Form Factor for the 123 Amax so we can figure out the real G7?

123 amax is not in the new book. 123 sst is though.