123gr ELD Match BC Discrepancy

[SlappyAbbot]

I just noticed that my Kindle copy of Hornady 10th Edition lists G1: 0.461 and the G7: 0.233. However, my box of Hornady Black lists G1: 0.506 and G7: 0.255. I only spent a few minutes searching for a reason behind this discrepancy, but did not find anything. So sorry if this is old news.

[NugginFutz]

I can’t speak to the 10th edition, but I do know that I was shooting this weekend out to 1000 yards using .506 G1 and I actually had to adjust my mv upward to account for the drop errors. (My hits were a couple tenths of a mil off at 1000 yards). I should have been using the .255 for those distances, but the fact remains that a .461 would have been off by a serious margin.

ETA:

Checking my own sources, Box of black matches your #'s. Hornady's 4DOF app for the smart phone agrees with the boxes.

What I find interesting is that your kindle's #'s do not align with any of the Hornady bullets listed on their website for .264 / 6.5 mm.

I would seriously consider forwarding a request for correction to Hornady and send a screen shot.

p.s.

Welcome to the board!

[SlappyAbbot]

Thank you. I figured I might send them an email, but wanted to confirm this was not a known issue.

[Bayouhunter1960]

[SlappyAbbot]

That might help explain it, thanks. I guess I'll just have to rely on box/website data.

[NugginFutz]

That being the case, why publish obvious erroneous data? A footnote would have sufficed, or just omit the data altogether, saving it for the next edition. Instead, they went with the "any data is better than no data" approach.

I wish they would show a little more concern over the accuracy of their information. What happens if this attitude crosses over into the load data section?

[Bayouhunter1960]

[Bayouhunter1960]

I’m not sure they are publishing erroneous data but I copied the rest of their explanation on differing BC’s for the same bullet, I wasn’t aware BC changes with range.
Their 10th edition lists the .264 123gr ELD Match SD: 252. G1 BC .461. G7 BC .233 MV range 1600-3300fps.

[centerfire]

BC changes with velocity.

[SlappyAbbot]

Compared some of the other ELD Match weights tonight (10th Edition vs website) and they are all similarly different. I guess that is not too surprising. However, the 143gr ELD-X is the same.

EDIT: I just sent them a message about it through their website to see if they have anything interesting to say.

[seven6twomm]

[SlappyAbbot]

I can’t speak to the 10th edition, but I do know that I was shooting this weekend out to 1000 yards using .506 G1 and I actually had to adjust my mv upward to account for the drop errors. (My hits were a couple tenths of a mil off at 1000 yards). I should have been using the .255 for those distances, but the fact remains that a .461 would have been off by a serious margin.

I was playing around with the 4DOF Calculator last night and it looks like the Axial Form Factor setting might help with this. I had no idea what that was, so was reading about it on their Instructions page and it made me think of this post.

https://www.hornady.com/team-hornady/ballistic-calculators/4dof-ballistic-calculator/instructions

[SlappyAbbot]

To date I’ve gotten the best BC data and bullet dimensions from Litz’ books or the Applied Ballistics app. If I get serious about shooting a bullet I’ll pay the $3 and buy the Custom Drag Model from them which is a ballistic coefficient based on velocity decay through the transonic boundary verified by live fire.

Thanks for your input, I'll look into that. Sounds similar to what Hornady is advertising in their 4DOF app.

[seven6twomm]

I never ran out and bought all the Applied Ballistics books right away but the app has been indispensable for me both as a shooting solution calculator and also a simulator to see what a bullet might do if it's going "x" velocity. The Custom Drag Models smartened things right up for me at distance, instead of being 8" low and 10" right at 700m, or missing at 1400m that shot is much, much closer to point of aim at all ranges. And it's cheap! $30 for the app...

[newb]

Not sure if this will help for real world results vs stated info, but I would use the lower stated BC and here's why.....

I recall others a few years back saying AMAX needed to use lower BC for drop calc so I used that for the base BC which was said to use 0.42.

The trajectory didn't line up and I did do proper scope center to bore measurement. There could have been an error on my part somewhere, but I didn't look into it and just used the real world results as calc values to me are a starting point to get close and then map actual real world data, re-plot from there.

22" barrel. AMAX chrono'd pretty close around 2510 fps and my origial cal value I put 2500 before I had chrono data. 100 yd zero.

300 yds called for 4.82 MOA, I was 7 MOA. 500 yds called for 12.73 MOA (mine is 1/4 MOA increments) and 12.75 did perfect. This was the furthest I used AMAX for, I don't recall if 750 yds or not so I'll just say not.

Finally ran out of my AMAX stockpile and used the ELD last week or week before and don't recall that fps off the top of my head, but I think the ones tested from this batch was a tad faster than AMAX. (all factory loads here)

I have new actual values written down and I'd have to dig. But I recall 500 yds changed to 15 MOA. 750 yds my old calc for AMAX stated 26 MOA, but I dialed to 29.75 MOA and lucky chance that was the required adjustment. 29/30 hits on the gong. I thought I would try to dial in better by 1/4 MOA about 3 rds in and that was the miss, went back to 29.75 and kept banging.