Gunsmithing Chamber (Throat) Finish, Poor Accuracy - See Pics

Clownbuster

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- 7 SAW I chamber (140gr VLD short throat), but he hand throated it for me to shoot the Berger 168's.
- 225 rounds fired, all Berger 168gr VLD
- Shoots 1.50"+ "gatherings" since new
- Powders used - H4350 and N555
- Proof TAC II stock
- Cleaned every 75 rounds, no brush, only pushed a jag and wet/dry patch, never pulled back accross the crown.

Based on these pics of the throat and crown, is this a realistic problem that would affect accurracy, or does this level of finish not matter?

Photo_20221122115132.jpg

Photo_20221122115139.jpg

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Clownbuster

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I inspected my other barrels finished by other builders to compare to (Lane Precision, LRI, GAP, Bartlein, SAC) and their finishes look smooth and uniform, crowns are perfect, even after 1000+ firings and regular cleaning. Thanks for the quick reply.
 
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Clownbuster

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Meh, that’s about what I expect when you say “hand throated”
10-4. The part of the throat that I thought looked really odd is on this pic. You can see the bright and shiny ring of the face of case mouth ending, then into rifling, then it has what looks like another case mouth ending further down the throat, then into the remaining rifling.
The hand-throating on my other rifles look smooth into the rifling. So weird.
Photo_20221122115132.jpg
 

JBoomhauer

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What are the chances he had a bushing that matches the 7SAW chamber? Prob one for a 7MM-08 with a bit of slop and you get what’s pictured above.
 
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Yondering

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What are the chances he had a bushing that matches the 7SAW chamber? Prob one for a 7MM-08 with a bit of slop and you get what’s pictured above.

Unless we're thinking of very different things, the bushing in an interchangeable bushing reamer fits the bore (well, more accurately it fits the lands), NOT the chamber. It does need to be sized to that specific bore but has nothing to do with whether it's a SAW or -08 chamber.
 

JBoomhauer

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Unless we're thinking of very different things, the bushing in an interchangeable bushing reamer fits the bore (well, more accurately it fits the lands), NOT the chamber. It does need to be sized to that specific bore but has nothing to do with whether it's a SAW or -08 chamber.
We must be.
 

JBoomhauer

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PTG uni throater locates on the lands and the shoulder of the existing chamber.

If you want a good fit, it is best to match the chamber bushing to the actual chamber.
 
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Yondering

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PTG uni throater locates on the lands and the shoulder of the existing chamber.

If you want a good fit, it is best to match the chamber bushing to the actual chamber.
Ok that makes sense, I’d forgotten about that PTG setup. I do mine in the lathe so it’s a little different.
 

Wannashootit

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    What are you talking about then?
    I’ve chambered a bunch of barrels and there is no other bushing except the pilot bushing on the reamer.
    Exactly....my first thought when I saw that post was "WTF is he talking about"??
    Obviously, he doesn't know himself.
     

    Praeger

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    In post #2 those photos show some severe circumferential gouges. In my opinion, there's no fixing that. At best have someone set the chamber back, but they may have to cut the entire tenon off. The muzzle looks fine.

    Edit - Just reread that this is a Proof CF barrel. Likely not enough breech end to set the chamber back. Hope you got some resolution to your satisfaction.
     
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    reubenski

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    Meh, that’s about what I expect when you say “hand throated”
    I've throated out about 5 barrels with a PTG Uni-throater. None of them look like that in a borescope. And they all shoot well.