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Rifles, Reloading, Optics, Equipment
Gunsmithing
Scarring Across the Chamber Throat a Problem?
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<blockquote data-quote="Pdvdh" data-source="post: 2210332" data-attributes="member: 4191"><p>Thanks Alex, </p><p>To clarify, those cutter tool marks in the throat are only present adjacent to one of the 5 grooves in the bore. The throat is clean adjacent to the other 4 grooves.</p><p></p><p>Which is why I was concluding this one groove must have been cut a little deeper than the other 4 grooves.</p><p></p><p>It's not conceivable the throat could be cut non-concentric, such that the throat is cut shallow adjacent to one of the 5 grooves, and a little deeper on the opposing side of the throat. If a floating pilot on the chamber reamer was somehow slightly offset from the 6 flutes that cut the throat, it should simply cut an oversized throat. The cutter with the largest offset would enlarge the throat to a uniform, but oversize, diameter.</p><p></p><p>I own this reamer, and the prior chamber cut with it left a clean throat, without tool marks from the groove cutter. Both .338 barrel blanks were from the same barrel manufacturer.</p><p></p><p>I measured the floating pilot bushing diameter today with a 0.0001" micrometer and it measured 0.3296". I'm not certain that's the pilot bushing my gunsmith used, because I haven't asked him that question yet. He may have a set of bushings and could have used one with a snugger fit in the lands.</p><p></p><p>We also measured the diameter across the throat cutting flutes on the 6-spline chamber reamer, and that measurement was 0.3386". </p><p></p><p>Both measurements seem correct for a .338/.330 barrel blank.</p><p></p><p>Now that you understand the cutter tool marks in the throat are only present adjacent to one of the 5 grooves, do you still feel the same way? As in... "Stop fretting. The only thing that barrel needs is shot."</p><p></p><p>Thanks for responding.</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 2210332, member: 4191"] Thanks Alex, To clarify, those cutter tool marks in the throat are only present adjacent to one of the 5 grooves in the bore. The throat is clean adjacent to the other 4 grooves. Which is why I was concluding this one groove must have been cut a little deeper than the other 4 grooves. It's not conceivable the throat could be cut non-concentric, such that the throat is cut shallow adjacent to one of the 5 grooves, and a little deeper on the opposing side of the throat. If a floating pilot on the chamber reamer was somehow slightly offset from the 6 flutes that cut the throat, it should simply cut an oversized throat. The cutter with the largest offset would enlarge the throat to a uniform, but oversize, diameter. I own this reamer, and the prior chamber cut with it left a clean throat, without tool marks from the groove cutter. Both .338 barrel blanks were from the same barrel manufacturer. I measured the floating pilot bushing diameter today with a 0.0001" micrometer and it measured 0.3296". I'm not certain that's the pilot bushing my gunsmith used, because I haven't asked him that question yet. He may have a set of bushings and could have used one with a snugger fit in the lands. We also measured the diameter across the throat cutting flutes on the 6-spline chamber reamer, and that measurement was 0.3386". Both measurements seem correct for a .338/.330 barrel blank. Now that you understand the cutter tool marks in the throat are only present adjacent to one of the 5 grooves, do you still feel the same way? As in... "Stop fretting. The only thing that barrel needs is shot." Thanks for responding. [/QUOTE]
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Scarring Across the Chamber Throat a Problem?
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