Odd 'step' in the bore?

[ssgross]

looks like a lot of copper in there from the second pic.

[RCS]

MrClark, I believe your modified BMG M1919 barrel would have been manufactured with a stellite barrel liner which would only extend part way
into the barrel. The stellite barrel liners are very hard and still used in modern US machine guns. The ring in your barrel is from the stellite liner
as it only extends for a short distance.

[mrclark303]

MrClark, I believe your modified BMG M1919 barrel would have been manufactured with a stellite barrel liner which would only extend part way
into the barrel. The stellite barrel liners are very hard and still used in modern US machine guns. The ring in your barrel is from the stellite liner
as it only extends for a short distance.

Many thanks Robert, I think you really are onto something there. A quick Google shows the liners pressed in at approx 6/ 7 inches, so allowing for cutting, threading and reprofiling, it would put this ring in the correct appropriate location of the butting from the liner to the barrel.

Very plausible, I will get some high resolution side images of the effected area in the new year. That should hopefully confirm one way or another.
If the liner is significantly harder than the rest of the barrel, then it would certainly explain why a slight rring has appeared, as the softer material gives way as opposed to the harder material, ultimately creating a very slight hollow...

Many thanks again Robert, it's certainly a possibility, every day's a school day!

[mrclark303]

The attached is a cutaway M60 barrel stellite liner, you can certainly see that this is a distinct possibility for the ring in my barrel

[Woodsy]

The Stellite liner is the most likely reason. As a gunsmith I have never found any need to own a bore scope. If something in a barrel is not visible to the trained eye then it is not likely to ever be a problem. I have had many customers over the years (that have purchased expensive bore scopes) come in to have non-existent problems "rectified". The only common problem that is not easy to see by eye is a bulge right at the muzzle, but it is easily detected with a bore plug gauge.

[RCS]

I can remember years ago when these BMG M1919A4 barrels in new condition were very cheap to buy. Gunsmiths would use these heavy barrels to
build inexpensive target rifles. Having to deal with the stellite liner was always a problem when these barrels were used on Model 1903 and US Enfields
Model 1917.

Mr Clark, the boys in the machine gun groups would really like your FAL on full auto down in Arizona as your barrel would last along time !