The value of a .30-40 Krag rifle mainly depends on its condition and whether it has modifications. As of 2015, .30-40 Krag rifles that are in poor condition are worth around $200, but a pristine model from the same year and style may be worth upwards of $2,000.
You can determine the condition of the rifle by examining it for rust or pitting either inside the bore or on the barrel, action or other metallic part of the rifle. You should also examine the stock to see if anyone has modified its length, or if it has cracks or any other damages. The presence of any rust, modification or damage significantly detracts from the firearm's value to collectors. The .30-40 Krag came in different configurations, and some of these models are more interesting to collectors than others. This firearm had a carbine (22-inch barrel) variation as well as a rifle (30-inch barrel) version, with minor changes depending on the year of production. The carbine model came with a shorter fore stock than the rifle model. The carbine models demand a premium price compared to the rifle models, and as a result, forgers have created and passed off fake carbine models as real ones by shortening the barrel and fore stock of the rifles.