I've been playing around with the M150 (Army RCO) and PVQ31A's (USMC RCO) myself using the M4, M4A1, and M16A4 in Arsenal. Here's what I've noticed, regardless of ammo types:
1. Both the M150 and PVQ-31A's perform exactly the same at various ranges.
2. Both the M150 and PVQ-31A BDC/Stadia lines are spot-on when using the 2D reticle.
3. When using the 3D reticle, the M16A4 stays pretty true to the BDC/Stadia lines.
4. When using the 3D reticle, all rifles in the M4 family (barrel lengths shorter than M16A4) fall short of the BDC markings.
-This becomes painfully apparent at ranges greater than 200m and becomes increasingly difficult beyond 350m to 400m+
-In other words, to hit a target at 500m, I had to use the 600m stadia line and aim high in the chest to hit center mass.
In the USMC, we use the PVQ-31A for the M16s and the PVQ-31B for M4s. Unless I'm mistaken, the Army's M150 was built for the 14.5" barrels much like the USMC's PVQ-31Bs. My guess is that the RHS team may have intended for the M150 to be used for the M4s and either forgot to fix them up, haven't gotten around to it, or...didn't know and just slapped an "M150" label on the PVQ-31As just for the sake of Army units having an RCO with an Army name on it. Who knows?
To recap: If you use 2D reticles, you'll never know the difference. 3D and PIP reticles however, will notice a retarded drop-off beyond 200m when using either model of RCO with anything shorter than an M16A4.
EDIT: You can change the game's preference under the RHS options in the ESC menu in-game, for those outside "the know" and want to investigate for themselves! Also worth noting is that the ELCAN optics seem to work fine for the M4 family of rifles for whatever reason regardless of 2D/3D settings. *shrugs*
