I've just done some testing.
I put 3 ship Su-30 flight 2KM in front of me, and I followed them with same speed and alt.
I gave all of those Su-30s one of the default CAP payloads that has R-77s and R-73s.
My frames from inside cockpit (max zoom out) were ~16FPS.
Now listen up.
I changed all Su-30s payloads with diffrent CAP payload that has all missiles except R-77s (it was a setup made of 73, 27ET, 27ER, 27T)
I fired up the mission again, same conditions of flight, and my FPS went up to ~35FPS, double of the previous FPS.
I switched those payloads back and forth several times, to be 100% sure that there's something wrong with R-77 model (it doesn't utilize LOD shapes maybe?)
Devs, beta-testers, please look into this issue. Probably there's more of that. I mean the problem surely is not limited to only R-77 model but some other models in the game as well.
PS. LockOn 1.2 release should be as polished as it can be. This must be truly platinum release, otherwise... I'll start black-mailing ;) Squish maximum performance of this engine by looking into things that actually screw up this performance. This really CAN be optimized.