Helli to the forum: I recently picked up a krag bayonet dated 1896. It will not fit on either of my 1898 krag rifles.the catch goes on ok it is the ferrule that is too small to go on the barrel. Was there a difference in barrel diameter between rifles? I have a 1901 dated bayonet that fits both rifles. There is no rust or Mark's on the inside of the ferrule.  Were these bayonets used on any other rifles? Maybe with a larger barrel diameter. It is smaller by quite a bit. You would have to real twist it hard to get it on the krag barrel. Any ideas? 

Sounds like an incorrect or modified bayonet. Can you post some pictures? Is anything else out of the ordinary with the bayonet?

Rifle barrels for all of the .30 caliber Krag barrels at the muzzle, as they were made at Springfield Armory,  were all 0.620 inches. (Except BoOF rifles.) Carbine barrels were 0.635 inches. That's why the PC and School rifles that were altered to be able to support a bayonet had the muzzle turned down slightly to fit the barrel ring/ferrule. So there should be no authentic variation on a regular Krag rifle.

I measured the inside ferrule it is .612. I think it is a krag bayonet. I could be wrong on that. Were these used on any other rifles?  I cleaned the grime out with steel wool. You would really have to force this on the barrel to get it to fit.

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It looks like a glob of paint or rust is inside the top of your bayonet 'ring'.

I suspect, if you cleaned the interior of the mounting 'ring', it would fit your barrel's muzzle.

A 20 gauge bronze shotgun brush could be put in a section of cleaning-rod and spun in a power drill to polish the interior; moistening with Hoppe's solvent would help.

I guess it's the lighting in the photo that looks like gunk or paint. The inner ring is clean with no obstructions. It still does not fit. I left the rest of the bayonet "as found". It seems to be about 8 thousands of an inch undersize.  I did not want to ream it out until I learned more about it. Thanks for the help.

It's not a rare or unusually valuable bayonet. I'd just ream out the ferrule a bit and you'll be happy. It looks fine otherwise.

Hard to explain what happened. It must have been altered in some way.

Good luck.

This problem is often the result of the ring being "squooshed" at some time, making the opening oval instead of round. Did you try measuring the opening at several points? Any difference?

Thank you for aiming me in the right direction. When I compared this bayonet to my other "good" one I could see that the guard was bent back towards the catch. Someone must have tried stabbing a tank to death with it!  I will try and bend it back where it belongs.
      Thanks again, kc