With the gun having been re-blued (frame),,it's been apart,,or at least he hope so! for the process.
Upon reassembling the NID and others with the same type set up like a Fox, it's strong bolt/top lever spring gives many some problems.
I've seen a few with a some-what weaker substitute bolt spring in place. I assumed to make re-assembly a more plesent job.
The guns will open up upon fireing if the bolt spring isn't up to specs. They will also do the same if the rotary bolt isn't closing properly onto it's rib extension cut.
Perhaps a replacement rotary bolt was dropped in when reassenbled to tighen 'er up and it made a nice 'lever to the right' situation and it looked good.
But isn't really locked securely and it shows itself with the bigboy loads.
Too many use the top lever as some sort of dial indicator arrow to read the lock up on doubles. It really has nothing to do with it.
Only a careful check and spotting in of the locking surfaces can really tell you how well it's engaged,, and how far along the wear is.
You have to feel and read the slop in the mechanism too. It allows lever movement after the bolt is secure.
If the lever was to the left, but the breech felt tight, most would be concerned.
Remove the lever and bent the tail slightly to the right to make it appear less wear was involved,,the same people feel fine about the lock up. It's done more often than most think.
A fine appearing lever to the right may be only catching the locking surface on the rib by a small amount. Appears all is well, shoots OK with field loads. But fails with Hi-Test loads.
Just a couple of possibles,,along with the plain old dirt, grease & crud in the mechanism suggested by 8bore.
If the frame & parts were hot-blued,,it is entirely possible that an incomplete flush of the blueing salts have left some inside there in the corners/edges.
Packed & hardened in there, it can interfer with the movement of the parts. Plus the stuff makes for rust as it absorbs moisture.
Plenty of things to look for..
