Depends on the serial number and what you mean by "automatic". Most will be worth around $700-$800, low serial numbers (under 8000) will bring in a couple hundred more.
A Winchester Model 140 12 gauge, semi automatic can be worth up to $150. The exact amount that the Winchester is worth depends on the condition of the gun.
federal reserve
50-300 usd
75-550 usd
200
50-500 usd
100-400
50 - 400 usd
10-60 usd
How much is my Ernest borel automatic Windsor watch worth, it's vintage 1960
50-550 usd
10-800 USD or so