Thread: 180 eldm BC

Worked up at pretty good load, went to validate it, only had a chance out to 500m, I’m using sterlock pro to true it. Do I trust the BC of the Eldm or the velocity from labradar, ether the speed is out 50fps or the bc is, what ya reckon?

I would think the labradar speed would be pretty accurate

Originally Posted by Tirau

Worked up at pretty good load, went to validate it, only had a chance out to 500m, I’m using sterlock pro to true it. Do I trust the BC of the Eldm or the velocity from labradar, ether the speed is out 50fps or the bc is, what ya reckon?

What bc are you using? There's multiple listed based on speed twist and range. Labradar is 1% accuracy so could easily enough be 25fps out.

Trust your Labradar.
Stick a G7 of .360 in your ballistic app and you’ll be damn close!

Maybe using the multi bc feature might true it up more, I just used the 0.391 G7 it had listed. Bullet should still be doing 2360fps at 500m

.391 is too high unless your running a sub 1 in 8 twist. Typically you want to use the mach 2 or 1.75 given BC as a start with the ELDs for any sort of range. For the 180 and a 1 in 8.75 that's 0.364 or 0.376. I use hornady 4DOF so I've always found it pretty close only needing minor tweaking.

Have a look at hornady.com/bc.

The twist rate of your barrel makes quite a difference. The bc changes with velocity too so make sure you use the correct value for each velocity range.

It’s a 1-8 twist, I’ll use the multi bc inputs and see how it’s looks. I was thinking the velocity wasn’t the problem.

You probably want to use Hornady’s BC for mach 2 or 1.75 and then adjust your velocity. Have a listen to The Shooters Mindset Episode 300. Near the end they address this directly.

I just used the 1 in 8.75” twist figures list on their BC page including the lower speed ones in BulletFlight and used my magnetospeed velocity figures. It has been spot on to 720m thus far which is plenty far enough for anything I will do. I think having a calculator that can use using all the mach figures is key and makes it more accurate