Matching ballistics between 6.5G and 308 Win

[BKKJ]

[depletedyourcranium]

No way to say without knowing what loads you're planning to shoot.

[Drillboss]

Here's a calculator to estimate velocity from different barrel lengths: shootersnotes.com/calculator/velocity-estimator/

Then use a ballistic calculator: https://www.shooterscalculator.com/b...tory-chart.php

Looks like the trajectories are pretty similar out to 600.

[Kswhitetails]

Welcome to the Horde! As stated above, trajectories are pretty similar, but there is a pretty severe delta between them in the energy and velocity numbers at the muzzle. Wait though, the G catches up and passes the heavier bullet soon, and with the lower recoil, puts an other round on target sooner too. If I remember right, if you compare them setting the Grendel zero to 200 yards, it's very similar. Except for wind, which the G wins by quite a bit.

[Sticks]

...Wait though, the G catches up and passes the heavier bullet soon, and with the lower recoil, puts an other round on target sooner too. ...

Not to mention a lighter overall rifle.

[Sputnik]

I would also add to compare the 6.5 Creedmoor into your mix. I believe Creedmoor beats the 308 and the .30 cal/7.62. The box of Hornady's Precision Hunter says 2700 fps with a 143 gr pill. Then you can reload 6.5 pills for both G and Creed. I believe I got a Creedmoor Criterion barrel from Fulton Armory that is way more accurate than I am.

[BKKJ]

Thanks all for the replies, I'm going to mess around with ballistics calculators a bit. Going to pick up a group buy 18 and hoping it settles in around 2500fps for most loads. am still waffling 308 or 6.5 Creedmoor on the AR10 build. Mostly due to plinking ammo cost. Also (to tie back into the original post) because I'm not sure what barrel length I want yet. Was entertaining either an 18 or 20 in 308. Probably would just go 20 in Creedmoor. I'm sure I don't "NEED" better ballistics than the 308. I'm just trying to decide if it's better to keep ballistics similar while upping energy or pay a little more and improve ballistics (that are already likely good enough) as well.

[ErikS]

I found in real conditions my 16in Grendel shooting 123s did not match my 308 past 300yds. Check the ballistic calculators closely and use realistic numbers for your Grendel. If you don't have a chronograph you won't know for sure so it take trial and error at ranges beyond 250yds or so.

[BluntForceTrauma]

ES, what bbl length for your 308?

[ErikS]

20in 308 vs a 16in Grendel. I found they differed quite a bit when I shot during a recent shoot that reached out to 460yds. I used a turrent marked for 308 and it worked great until the long 460yd shots, I was low with my Grendel.

Grendel load, 123 ELD at 2350fps
308Win, 168 SST at around 2600. (not as sure about the speed of the 308 load)

I was shooting at steel IPSC targets so any differences at the 350 and in targets were still on steel.

[LRRPF52]

24" vs 24"
123gr SMK vs 175gr SMK

They're within .2 mils of each other out to 700yds for trajectory and .1 mils wind, in the Grendel's favor.

What I've personally seen from behind the spotting scope and with actual drop data is that the Hornady 123gr bullets fly about the same flight path as a 175gr SMK.

The 6.5mm 123gr Scenar and 123gr SMK have an edge over the .308 175gr SMK.

Where the real advantage lies is that shooters behind a Grendel can see their own impacts easily because the rifle didn't come off target as much as the .308s do, so follow-ups are much faster, as is the learning curve since you can see as a shooter what is happening, versus needing a spotter.