Possible Underwood Carbine Purchase

[painter777]

Is there finish loss on the top of the left lug of your bolt ?

I ask after seeing your bottom view of receiver picture increased, it shows what appears to be filing where the bolts left lug would ride / rotate. Burrs are a issue to look for here since the bolts left lug rotation if it binds can lead to a broken right bolt lug. It's possible it had some burrs that were filed or sanded to smooth the area. Look and feel this area over closely. A piece of worn / oiled emery cloth works well to smooth the inside of the ledge out. Clean out all shavings and be sure to lightly grease both inside tracks that your bolt lugs ride in. Currently yours shows scars that extend outward, best they would run length wise with the rail.

Zoom in:

https://www.milsurps.com/attachment....7&d=1693421347