Hi Folks
I've been a member for a whole 90 seconds and I'm off to the races already...
Seems I tickled the fancy of a retired machinist friend of mine when proposing the notion of building a 50BMG from scratch (mostly). In a haste to grab some barrels when I saw them, I've ended up with a couple of brand new, M2HB barrels that were part of the Sabre Defence liquidation. They weren't finish treated yet (parkerized) but otherwise are finished/chambered. What I didn’t realize was some very important details when I ordered these barrels. My quick-to-act ASSumption was they would be 41V50 steel, parkerized, have a 1.5”L x 1.5”D x 12 tpi tenon, and… well, that’s basically it.
Well… they’re just so, so much more. They’re made from MIL-S-46047 steel, have a 0.770”L x 1.450”D x 8 tpi tenon (that turns out is just the end of a threaded, steel, chamber insert, screwed in to anchor the stellite as well as form the chamber), and are stellite and chrome lined. Wowza. Needless to say my plans to “simply” cut an inch or two off the chamber end and re-chamber, re-thread, re-profile are now vaporized. Or have they…
I also own a decent bore scope. Lemme tell ya, I am thusly conflicted by what I saw. Now the stellite section isn’t anything to get all goose-bumpy about. Its not bad and is still more uniform and slick than most off the shelf, under $1,500, button rifled barrels I’ve seen. Cool enough. But the chromed section of the bore… Lordy, Lordy… now that portion is some slick looking bore’ness.
I have some pretty decent barrels in my collection that shoot solidly in the 2’s and these barrels are every bit as nice “looking” as the nicest of them. Its bore’ing to look at it with the borescope (gun-pun for effect) as the whole length of the monstrosity of a barrel is just completely “unfeatured”. No chatter, no hashing, no rolls, burrs, tooling marks, divits, diggers or Buick’s. Just monotonous, monochrome, symmetrical, uniform, featureless, land-groove, land-groove, etc. I did manage to read, post-purchase, about the innovative bore consistency quality that Sabre Defence developed for their M2 barrel. Granted I’m referencing off the limits of capacity of my naked vision through the borescope, but all indications are it wasn’t snake oil they were selling. Their claim to produce a 5 tenths or better bore/rifling/land consistency isn’t a hard swallow by looking at the bore.
A uniform, consistent, in-spec bore that is additionally chrome lined… what’s not to like for the shooting and longevity aspects. I have a mil-spec M4 barrel (yes, “M4”... as in is M16, M4 variant, chrome lined, with the anemic Govt profile, and ever-so-necessary grenade launcher relief cut...) that is one of my 2’s barrels (slow fire) with the good ammo. The wheels are turning…
Now, the stellite only protrudes 12” down the bore. I could still cut the barrel there and start fresh from that point. But then I’d have to have a carbide reamer to get through the chrome… in 50 bmg. Those are EVERYWHERE and CHEAP I’m sure. I’ve never turned with a carbide reamer either, and thereby, never through chrome. My friend seems to think that undertaking might be a proposition in expensive learning as to how to use such a large reamer in carbide on hard chrome. I have to very seriously consider his 55+ years of experience. We are considering a boring bar to rough it and finish with a HSS reamer, but the boring bar will only get the body up to the neck. The nose of the HSS reamer would still take it hard.
So, all the above rambling converging on these queries I’m hoping some can shed light on:
1. is it possible to ream a 50 BMG “match chamber”:
---a. in a chrome lined bore?
---b. with a carbide reamer?
---c. without breaking the reamer?
2. what will the long term effect of throat erosion look like at the exposed junction of hard-chrome and 41v50 that will be in the throat?
3. decent, long range accuracy being my objective ,should I:
---a. cut my losses and suck up the shipping and return these and buy Lilja, Green Mountain, or other blanks?
---b. keep my patience in check and head engaged and develop something novel that is entirely possible?
---c. file for divorce now because when the war department realizes what I’ve already spent on this “save money by making it mysef” project I’ll just have the paperwork done under less stressful conditions?
---d. some combination of the above?
My apologies and thanks for your reading through this, and especially if anyone cares enough to offer anything constructive for me to consider.
-w
I've been a member for a whole 90 seconds and I'm off to the races already...
Seems I tickled the fancy of a retired machinist friend of mine when proposing the notion of building a 50BMG from scratch (mostly). In a haste to grab some barrels when I saw them, I've ended up with a couple of brand new, M2HB barrels that were part of the Sabre Defence liquidation. They weren't finish treated yet (parkerized) but otherwise are finished/chambered. What I didn’t realize was some very important details when I ordered these barrels. My quick-to-act ASSumption was they would be 41V50 steel, parkerized, have a 1.5”L x 1.5”D x 12 tpi tenon, and… well, that’s basically it.
Well… they’re just so, so much more. They’re made from MIL-S-46047 steel, have a 0.770”L x 1.450”D x 8 tpi tenon (that turns out is just the end of a threaded, steel, chamber insert, screwed in to anchor the stellite as well as form the chamber), and are stellite and chrome lined. Wowza. Needless to say my plans to “simply” cut an inch or two off the chamber end and re-chamber, re-thread, re-profile are now vaporized. Or have they…
I also own a decent bore scope. Lemme tell ya, I am thusly conflicted by what I saw. Now the stellite section isn’t anything to get all goose-bumpy about. Its not bad and is still more uniform and slick than most off the shelf, under $1,500, button rifled barrels I’ve seen. Cool enough. But the chromed section of the bore… Lordy, Lordy… now that portion is some slick looking bore’ness.
I have some pretty decent barrels in my collection that shoot solidly in the 2’s and these barrels are every bit as nice “looking” as the nicest of them. Its bore’ing to look at it with the borescope (gun-pun for effect) as the whole length of the monstrosity of a barrel is just completely “unfeatured”. No chatter, no hashing, no rolls, burrs, tooling marks, divits, diggers or Buick’s. Just monotonous, monochrome, symmetrical, uniform, featureless, land-groove, land-groove, etc. I did manage to read, post-purchase, about the innovative bore consistency quality that Sabre Defence developed for their M2 barrel. Granted I’m referencing off the limits of capacity of my naked vision through the borescope, but all indications are it wasn’t snake oil they were selling. Their claim to produce a 5 tenths or better bore/rifling/land consistency isn’t a hard swallow by looking at the bore.
A uniform, consistent, in-spec bore that is additionally chrome lined… what’s not to like for the shooting and longevity aspects. I have a mil-spec M4 barrel (yes, “M4”... as in is M16, M4 variant, chrome lined, with the anemic Govt profile, and ever-so-necessary grenade launcher relief cut...) that is one of my 2’s barrels (slow fire) with the good ammo. The wheels are turning…
Now, the stellite only protrudes 12” down the bore. I could still cut the barrel there and start fresh from that point. But then I’d have to have a carbide reamer to get through the chrome… in 50 bmg. Those are EVERYWHERE and CHEAP I’m sure. I’ve never turned with a carbide reamer either, and thereby, never through chrome. My friend seems to think that undertaking might be a proposition in expensive learning as to how to use such a large reamer in carbide on hard chrome. I have to very seriously consider his 55+ years of experience. We are considering a boring bar to rough it and finish with a HSS reamer, but the boring bar will only get the body up to the neck. The nose of the HSS reamer would still take it hard.
So, all the above rambling converging on these queries I’m hoping some can shed light on:
1. is it possible to ream a 50 BMG “match chamber”:
---a. in a chrome lined bore?
---b. with a carbide reamer?
---c. without breaking the reamer?
2. what will the long term effect of throat erosion look like at the exposed junction of hard-chrome and 41v50 that will be in the throat?
3. decent, long range accuracy being my objective ,should I:
---a. cut my losses and suck up the shipping and return these and buy Lilja, Green Mountain, or other blanks?
---b. keep my patience in check and head engaged and develop something novel that is entirely possible?
---c. file for divorce now because when the war department realizes what I’ve already spent on this “save money by making it mysef” project I’ll just have the paperwork done under less stressful conditions?
---d. some combination of the above?
My apologies and thanks for your reading through this, and especially if anyone cares enough to offer anything constructive for me to consider.
-w