I've been running some ballistics calculations on my computer and think I might get away with this idea, let me know what you guys think:  

My hypothesis:  Can I use 16" bbl calibrated ACOG on a 20" platform to fire 75gr HPBT and still use the bullet drop stadia with success?  

My ballistic calculations say there would only be about an 1" difference in bullet path between the two rounds.  Anybody mix and match ACOGs and bullets in the field?  If so, what did you find?

Quoted: My ballistic calculations say there would only be about an 1" difference in bullet path between the two rounds.  Anybody mix and match ACOGs and bullets in the field?  If so, what did you find?

What  bullet & MV is the RCO calibrated for?

I'd say that most people are shooting an ACOG with a different setup than what Trijicon spec'd the reticle for.   You need to get out to a KD range and figure out your hold overs in any case.    You're probably at a different elevation anyway.