Depends on the gun. I have one that weighs less than one pound, and one that weighs 23 pounds. There is no one weight.
A tiny bit less than a maxi gun.
5 lbs and up
418lbs.
Depends on the size of the barrel.
Depends on the specific model/caliber.
800 lbs.
About 4-6 pounds.
In a pistol grip grease gun each pump weighs 33 grams.
2 lbs. 2 oz
Contact the maker.
Depending on caliber, they can ragne from 4-28 grains.
About 26 lbs. Some info for you: http://en.wikipedia.org/wiki/M240_machine_gun