Basically you are looking at a "parts" gun, with no value for the barrel...especially if the bore is questionable. If it is an original gun the collectible value is virtually nil. From your basic description it sounds like a kitchen table gunsmith sporterized gun...no insult intended. Mooncoon is not far off with his estimate, though I would break it down a bit.
Condition is an important factor to determine the value...the prices below are based on very good plus condition with 50% finish, no rust, or broken metals parts.
To break it down here it is...it may not be acceptable to most people;
Receiver, c/w Breechblock, firing pin, cam latch--$120.00
Lock, c/w hammer and ALL internal (as long as it is functional)--$125.00
Trigger guard and plate, One piece M1888 style, c/w sling swivel-$50.00
Trigger guard and plate, two piece bow style c/w sling swivel--$75.00
Forgot to mention..just in case the trigger guard and plate are actually the carbine style detail photo of same to determine the variant. There were rifle trigger guard bows which were modified to resemble the carbine bow
Trigger guard and plate, Carbine, two piece bow style, short leg variant--$200.00
Trigger guard and plate, Carbine, two piece bow style, long leg variant--$100.00
Butt plate--$30.00
Lower barrel band, notched for Buffington rear sight--$20.00
Lower barrel band, not notched--$40.00
Cut-down stock- $00.00
Barrel, cut down--$00.00