Buying takeoff barrels... some musings, learn from my mistakes, and are these worth trying to fix?

[atblis]

Not a cut rifled barrel, it's button rifled- far as I know, that button can't do anything but follow the hole and it's gonna press the grooves in equally- but I'm not a barrel manufacturer.

The video seemed to show the grooves consistent the rest of the way up the barrel. I honestly can't think of a way I could cut a chamber that would look like that if I TRIED. Variation of some thousandths in freebore length is poor/non-concentric setup. Going from zero freebore at the neck to whatever on the very next groove is something I've never seen. Only thing I can think of is that the blank was defective- gun drill wandered (probably all the way up the barrel, who knows) around and it should have never made it past that point, every manufacturer checks for straightness of the hole before rifling. JMO YMMV

That might explain it. The bore is basically a spiral. The button tracks it as it's pulled through so the rifling doesn't show the issue but chambering does.

 

[hemiford]

The reamer pilots in the virgin rifled bore, correct ? If it's a proper tight pilot fit, the reamer must be concentric in the rifled bore.

Then the reamer spins. It does not wobble non-concentrically, does it ?

How could the chamber possibly be non-concentric to the bore ?

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The barrel's external profile is cut on the same center axis as the bore axis, right ? The bore is not off center in the barrel is it ?

 

[tobnpr]

How could the chamber possibly be non-concentric to the bore ?

From a defective barrel, mostly.
In it's simplest form, the blank is placed between centers, and a steady rest replaces the tailstock center. With a decent barrel, it's mostly impossible to eff it up. There's a STRAIGHT, rifled hole between the centers and the reamer simply follows that hole. Many still chamber this way. Direct indicating the bore is what most of us do nowadays, but that's a different animal.

If the rifled hole is not straight between centers, or wanders in the last few inches of the cylinder where the chamber is cut you end up with a non-concentric chamber. This typically results in minor but still visibly "uneven" starts of the lands at the leade. Like I said, never seen one like that in the photo.

 

[HSmithTX]

It is very easy to bend a reamer, you can bend a reamer a LOT too, if the reamer isn't set up concentric to the bore or if the bore isn't axially aligned to the reamer well you will get a crooked chamber and if it's bad enough the chamber won't be round. The big end of the reamer will overcut as well if the alignment isn't good. If the pre-drill for the reamer isn't straight same thing. This is all basic machining, not high end gunsmithing.

 

[LRNut]

I did last year, a guy sold me a 24"
I should of new better, ran a bore scope through it and was told only 100 rounds shot. There was little to no rifling 5r.
Never tried it, but I wasn't going to waste my time.
I will Not Ever Buy a used barrel again.
And yes it was a 300RUM.

I would never buy a takeoff barrel. For that matter, I am always skeptical whenever someone posts a rifle for sale that supposedly "shoots lights out - only 100 rounds down the barrel." Really? Why sell it then? That said, I bought a .338 Edge from a guy on another website and it does shoot great - just shot it at my 906 yard gong. But he was moving to BR and wanted to raise money to buy his own lathe.

 

[xr650rRider]

From a defective barrel, mostly.
In it's simplest form, the blank is placed between centers, and a steady rest replaces the tailstock center. With a decent barrel, it's mostly impossible to eff it up. There's a STRAIGHT, rifled hole between the centers and the reamer simply follows that hole. Many still chamber this way. Direct indicating the bore is what most of us do nowadays, but that's a different animal.

If the rifled hole is not straight between centers, or wanders in the last few inches of the cylinder where the chamber is cut you end up with a non-concentric chamber. This typically results in minor but still visibly "uneven" starts of the lands at the leade. Like I said, never seen one like that in the photo.

I've got a 6BR Krieger from a well know gunsmith in Pennsylvania that has a chamber just as crooked as the one in the video. I bought and had 2 barrels chambered at same time for 2 Kelbly Stolle Pandas. I poured chamber casts when I received them. Before the cheap borescopes were available. Crazy thing is it still shot pretty well. You expect to have quality job done but I think more times than not, these get subbed out to the high school apprentice. One other lousy chamber job from an outfit in Texas and bough my own lathe.