I'm doing a 20" AR10 build and plan to shoot Lake City M118LR through it pretty much exclusively. I also like ACOGs. Are all the .308 ACOGs' BDC reticles calibrated for M80 ball or is there one that fits this load?

They are calibrated for 168 grains out of 20 inch barrel. It's probably close enough to M118LR for a low power scope.

Some are calibrated for ball but most seem like they are made for 168.  Go to their site and do some looking around, you'll find  which models that are made for ball. Also dont worry too much about the barrel lengths they have listed, my ACOG was calibrated for ball out of a 24 inch M240 but my holds are dead on out to 600 yards from my 16 inch AR10.

This. Zero where you want it. Youll be good.

I have a buddy using a 556 ACOG on his 308, and it works pretty good to 400ish yards. After that, it gets weird. I think he zeroed at 100yds and just wings it basically.

I think you’ll find it’s not really going to much matter. ACOG BDCs are one of those things people get really nit picky over from looking at it on paper, but never really notice in actual use. If you make an even vague attempt to match it up, you’ll be fine.

If you’re still stressed over it, zero it at a further distance than 100m to split the ballistic difference. Sometimes being an 1” off at 100 can trade into being a foot closer at distance. You’ll have to be the judge of where you want that tradeoff to be based on how you plan to use it. Use a ballistic calculator if you go this route though, and honestly you’re probably better off just zeroing @100 and calling it a day.

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You can use a ballistic app like Strelok to work out theoretical dope for your load. After you zero it on a short range make final adjustments out at 400yds or so and the rest of your dope should be close enough to ding steel out to the bottom of the BDC. You might end up shooting an inch or two high or low at 100yds to get the rest of the BDC to line up but that doesn't really matter.

TA11E. 168gr SMK at 2600 or 2650fps. JBM says the difference with a slightly slower 175gr SMK is <0.25 MOA at 600yds.

Shooter's Calculator backs JBM up on that and the TA11 is IMHO the best series of ACOG anyway. Thanks gents.