It depends on who made it, where it was made, how old it is, what condition it is in, any accessories and whether it has the original box and papers. You are in the 100 to multiple/tens of thousands price range until more information is providecd. To put it in a car frame of reference, you have a Ford. Whether it is an Escort or a Shelby GT is unknown.
Without more informaiton, rang of 100-1000 USD
Value is too difficult to be accurate without seeing the gun. Condition which includes the amount of original finish and original configuration will determine value. A BAR can run $300-$1000 depending on grade and condition. Rare High Grades will be valued higher. Recommend taking it to a gun shop for appraisal.
No. The M203 is a grenade launcher.
50-150 or so
Could be a rifle, shotgun or handgun.
shoot it in the head with a 30-06 rifle or any high power hunting rifle.
www.pilkguns.com
10-1000 USD depending on specifics
25-100 usd
As a general rule, used optics, unless high end, do not have much value. 50-100 max.
50-100 dollars
These were heavily mass produced. They are not rare and not terribly high value.