Noticed a significant fps lag whenever using a full auto weapon whilst zoomed in. This can be through an RCO sight or that of an armoured vehicle. Issue only seems to occur when zooming in with 'focus mode' (holding right click down) or through magnified scopes - and always when firing in large bursts.
Went from 72 frames per second to 52 fps discharging an MX (regardless of optics) whilst holding down right mouse button.