kiwi49
Well-Known Member
Wonder if an apprentice did the job? Smith thought it was OK, so you got it. I would send the barrel back to the manufacturer.
Scarring Across the Chamber Throat a Problem?
- Thread starter Pdvdh
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Rflshootr
Well-Known Member
For what barrels cost these days, I'd send it back. You paid for first quality and that is what I'd expect to get. I'd also make who ever chambered it aware of the situation. Mind if I ask the brand?
A major manufacturer of cut rifled barrels. That should suffice. Not even 100% certain what's amiss yet. But I've got a pretty good idea.
Thinking I'll run it past the manufacturer, with the photos, after the holiday weekend.
I don't think the Smith that cut the chamber has anything to do with this issue.
Really looking like the groove cutter cut too deeply in the one groove. Such that after the chamber reamer cut the throat, the tool marks from the cutter remained. Would be no way for anyone other than the barrel manufacturer to catch this prior to cutting the chamber.
Barrel manufacturers hold some incredibly tight tolerances. So they must have a way to monitor the depths the grooves are cut. It probably requires expensive equipment that only a barrel manufacturer would have on hand. Don't know how they QA/QC test their finished barrels prior to shipment.
I suspect a groove cut a mere 0.001" too deep would cause this to show in the throat. Because this bore should be .338" diameter, groove to groove. And this throat should be .3385" diameter. Doesn't leave much room for even a 0.0005" over-cut groove depth.
Thinking I'll run it past the manufacturer, with the photos, after the holiday weekend.
I don't think the Smith that cut the chamber has anything to do with this issue.
Really looking like the groove cutter cut too deeply in the one groove. Such that after the chamber reamer cut the throat, the tool marks from the cutter remained. Would be no way for anyone other than the barrel manufacturer to catch this prior to cutting the chamber.
Barrel manufacturers hold some incredibly tight tolerances. So they must have a way to monitor the depths the grooves are cut. It probably requires expensive equipment that only a barrel manufacturer would have on hand. Don't know how they QA/QC test their finished barrels prior to shipment.
I suspect a groove cut a mere 0.001" too deep would cause this to show in the throat. Because this bore should be .338" diameter, groove to groove. And this throat should be .3385" diameter. Doesn't leave much room for even a 0.0005" over-cut groove depth.
Rflshootr
Well-Known Member
No the smith didn't cause it but, and the reason I mentioned it was because he may cut you a little slack on chambering a new barrel since you already paid for the first one if it comes to that.
If the barrel is a custom, such as a Bartlein, Brux, Kreiger or the like, and suppose to be within .0002-.0003, that tolerance isn't there and should have been scrapped and not sent out the door. If it is a cheaper brand barrel, then it is what it is.
And yes, they use a thing called an air gauge that is capable of measuring .00005. That's 50 millionths or one half of .0001.
And if it was suppose to be a hand lapped barrel, the finish isn't there either. Again it shouldn't have been shipped out.
If the barrel is a custom, such as a Bartlein, Brux, Kreiger or the like, and suppose to be within .0002-.0003, that tolerance isn't there and should have been scrapped and not sent out the door. If it is a cheaper brand barrel, then it is what it is.
And yes, they use a thing called an air gauge that is capable of measuring .00005. That's 50 millionths or one half of .0001.
And if it was suppose to be a hand lapped barrel, the finish isn't there either. Again it shouldn't have been shipped out.
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Thanks for sharing that information. Learning from you. That's why I posted the Thread. Increase my understanding of this snafu, and how it might have happened.
Trust me... this is a mainstream manufacturer of aftermarket barrels. Custom barrel profile and Carbon Fiber Wrapped. Special ordered, expensive, and with a prolonged turnaround time after the order was placed. So I'm discouraged..., but hoping to get it sorted out. Hoping for that Fairy Tale ending.
Trust me... this is a mainstream manufacturer of aftermarket barrels. Custom barrel profile and Carbon Fiber Wrapped. Special ordered, expensive, and with a prolonged turnaround time after the order was placed. So I'm discouraged..., but hoping to get it sorted out. Hoping for that Fairy Tale ending.
Rflshootr
Well-Known Member
I wish you all the luck possible.....hope it all works out and your rifle shoots 10 shot groups in the .1's when it's all said and done.
Bob Wright
Well-Known Member
That's sad. With long turn times, getting a bad one really hurts. It just doesn't happen often and am really feeling bad for you. Wow....
I didn't read all the replies but to me it looks like an archive left behind from a reamer throat diameter that is very close to groove diameter, and didn't totally clean up the surface finish in the groove. Personally I'd run a brush through it a few times, patch it, and shoot it.
The cutter tool marks only extend into the throat from one groove. The rest of the throat is smooth.
I'd expect the tool marks in the throat to be present next to each groove in the bore if the throat was simply simply cut too small in diameter.
Or this single groove was cut too deeply.
If the throat wasn't concentric, I think tooling marks would extend into the throat from more than one groove. However the tool marks only extend into the throat from one groove.
Also, it would be unlikely to cut a non-concentric throat with the roller shaft on the chamber reamer located so close to the throat.
I think it's most likely a difference in the depth of a single groove. The groove with the tool marks extending into the throat having been cut too deep. Or at least some burrs on the cutter cutting too deeply in that groove. Don't absolutely know that, but I think that's the most plausible explanation.
Rflshootr
Well-Known Member
I would document it to the barrel maker with the pics and ask them how they would like you to proceed. Let them make the decision. That way, they can't say you damaged it by some means and it's not their fault.
