As with any firearm, it is not possible to accurately appraise a gun without seeing it. Condition, and original configuration will determine value. Other factors such as rarity of caliber or guage and higher grades have significant impact on value. Recommend that you see a local gun dealer for an appraisal. You can also do your own investigation by looking at other models being sold that are in the same condition as yours. Try the gunbroker.com or a periodical called "The Gun List" You can also reference the Blue Book of Gun Values which can be purchased on line at various retailers.
Check out www.corsonsbarrels.com, but looks to be around 200 to 220.
It's a good gun. We hope you are enjoying it.
100-350 or so
50-275 usd
Measure it, or have a gunsmith measure it, with a choke gauge.
80-200
around $125, if in good shape
2400
Need to know if it has the box, papers, accessories, gauge, barrel length, choke, condition, finish.
They usually use a modified (medium) choke on the 870, unless it has choke tubes.
The Winchester 140 12 gauge has a choke barrel at 28". This is the same choke size as the 20 gauge model.
That depends on many factors. When the gun was made, finish, length of barrel, choke are all things that can affect the value.