Quick translation: co-witnessing is when you get an eotech style sight and essentially merge it into the stock sights. You introduce a failure point to a system that was previously very reliable, thus it is a bad idea tactically unless you have a quick release on it so you can rip it off and check ck it when it fails.
LOS is line of sight......iron LOS is the line of sight using the 'stock' iron sights
VFG is vertical fore grip. Attaches to the forward rail, if you have them. Some people prefer them....... some have a bipod that springs out of the bottom. The one on my FAL does this and I've found it useful and stable.
Anyway, good morning
