That's not that hard to drill, especially since you can come from both ends. My quick take is that getting rid of the rifling on an existing barrel would be worse, at least on the tool.
I've bored through a .450" bore. The difference between minimum and maximum groove diameter isn't as much as you may think. What is tougher on the tool is not enough torque and rigidity to make a significant cut without burnishing and work hardening.
What sort of performance are you expecting from the completed spindle?
My existing spindle was made to the supplied drawing.
It is somewhat less than perfect.
Gunbarrels are not particularly hard ,RC 30 being typical........the reason being so they bulge ,not burst into splinters.
True. but they are not made of butter steel either. Leadalloy300, 12L14, leaded steel, is a dream to machine.
While extremely malleable and free machining it is what it is, heat treat isn't really an option.
Maybe check out green mountain barrel blanks gunsmith specials
Even if not 50 cal you can still ream it out in a few steps
I actually investigated this. The issue at the time was my 1.375" major dimension.
If you want to increase the hardness after machining send it out for nitride
No need for nitriding here. There really isn't any wear surface. For this purpose it's over all section moduli that is driving this. Even if tempered back significantly from a heat treat the 41xx series steels will/would "ring". Machined and ground as is they are still a bit "dead".
That's the one thing that 12L14 has going for it, it's dead as hell and resists any resonant effects.
Some 50 BMG barrels are stellite lined.
This I did not know. I had heard of nitriding and several failed chrome experiments, but this is new to me.
I didn't spend much time around the 50 BMG while I was in the service. When I finally did it was the early days of gun drilling truck axels more than anything M2 related.
Hey, just in case you're interested, I make the new, and aquire quite a few of the old, chrome rods 1-3/4" diameter. 19" deep gun drilled 1/2" dia. for tempsonic sensors. I make them regularly for one of my industrial customers. If you'd like one or two shoot me a PM. Most are 1045 but I may have one in 4140. You will still need to bore it out a little if you want that .531"+ bore.
Interesting and Thank You! I'll get contact information out today. Tempsonic sensors? Twice in one thread I get edgeumucated ;-)
12L14 which cuts like butter.
I'm well aware. See above.
The US Army cuts up all of the old barrels with a torch, so finding a worn out govt barrel is out.
I haven't had a huge issue finding surplus barrels. My issue is I don't need a serviceable barrel. It isn't even convincing my long time sources that it will never be fired again. It's the underwriters, insurance, attorneys, and the courts that make this difficult if not impossible.
If you can find a chunk of used .50cal EPVAT test barrel, that would be an easier piece to work with as they are made of 4140 or 416R and other than the collar end that fits into the Universal Receiver are a straight 1.625" dia. OD.
If I'm thinking about the same thing these tests rarely result in a total failure and the examples with significant degradation are kept in a library of sorts.
Thank You all.
Dennis
