FPS Lag aiming down the sights?

Hey, I got Rust recently and I have been having this issue that when I aim down the sights (Mainly the M4) I get FPS lag I have set my render quality all the way down tried various commands to in the console to try and stop it but still, I am getting this FPS lag. I have re installed Rust and Steam but still the problem persists.

I am stuck for ideas and I am not sure what else I can do and I am hoping someone here can help me out.

My PC Spec is:

NVIDIA GeForce 650TI 2GB
AMD FX 6100 (6 CORE @ 3.3Ghz)
16 GB RAM
750 Watt PSU

check the console when you aim down the sights, anything?

Nope, nothing at all