100-1000 depending on specifics
Gas operated
Your Browning B-2000 semi auto shotgun which was made in 1979 will bring between 275-425 dollars for a model showing between 60%-90% of its original finish,and a good bore.
This shotgun was manufactured from 1990-1993 in Belgium and assembled in Portgual, "g" stood for gas operated and there was another model called the a500r. The "r" meaning recoil operated. The receiver looked similar to the a-5 model, just not so square. These guns were replaced with the Browning Gold series.
the gas operated A 500 G lettering is gold. Is G for gas? then maybe red is for R is for recoil, which is how the A 500 R operates
"BLR" = Browning Lever Rifle It is lever operated
Your Winchester model 1400 semi auto shotgun is gas operated.
Your Browning B-80 in the description you described is valued at 450 dollars.
50-600 usd
My understanding is that the first true gas operated automatic shotgun was sold by Sears & Roebuck in 1955 as the J.C. Higgins Model 60 and was manufactured by High Standard.
Gas operated, pump, lever, bolt, box lock
The quick answer is a .410 bore - but there are relatively low recoil 12 ga. guns as well. Browning made a "recoiless" trap gun which almost is recoiless. In general, a gas-operated semi-auto will have less recoil, and in some cases this can be combined with a recoil-absorbing stock.
The main 2 reasons would be that your Browning auto-5 shotgun needs a good cleaning of the chamber and gas system,or your shotgun has a broken ejector/or extractor.This 2nd reason would require a gunsmith to repair.The first reason you may do yourself,or take it to a gunsmith and have him determine the overall problem.