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Gunsmithing Funky throat pictures on a fresh cut barrel.
- Thread starter NVScout
- Start date
As the title says.... it’s fresh cut . In not asking if I should shoot it or not , I’m asking what would cause that as I have not seen it before.
Your barrel is not perfectly round in the groove. So the start of the lead angle is hitting the high spot. Not uncommon. I'd be more concerned with the ragged looking edge on the the land in the upper part of the picture.
What are the chances that the grooves are oversized ? Say .3085 , when the camber would be cut it would leave in some groove ? All the grooves should be high if I understand what your saying? Every groove looks similar to that picture. I have a video that would be better but can’t figure out how to post.
That looks like their button(assuming it’s button rifled) might have had a worn corner. Do all the grooves have the same pattern? Or is it a cut rifled barrel?
Nvm sounds like all the grooves have the same pattern making me think it’s cut rifled and the cutter was cutting a little deeper on one side of the groove.
Nvm sounds like all the grooves have the same pattern making me think it’s cut rifled and the cutter was cutting a little deeper on one side of the groove.
Undersize wouldn't explain the hump/wave at the end of the freebore. You're talking millionths of an inch here. It could be from lapping. I see it all the time. Sometimes a crazy pattern. Uniform but crazy. Just shoot it.
It does not look like it in picture. It looks pretty normal to me. If the grooves are oversize,you'd see them in the free bore. I did have a batch of barrels where rifling was still visible (all of them evenly) in the free bore. The reamer was verified on size. Without going any further measuring, I sent the barrels back and they are being replaced.
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The picture is of GROOVES IN FREEBORE. People look at it like it’s a normal cut of lands , but those are grooves .... top left corner of pic shows the land .
Fire some rounds to get everything black and you won't notice it anymore.
Everyone who’s posted knows it’s the groove. As stated, not uncommon at all. A hook cutter cut that groove. The cutter is not perfect. The left side of the cutter cut a little deeper than the right side. This is also why it’s present in all the grooves. As Ledzep stated, if the groove diameter were large, you’d see evidence of lands in the freebore.
Edit: If I was to guess how much shallower the right side of that groove was, there’s probably five zeros in front of that number. Inconsequential. Just shoot it.
I’m not sure I understand. Every chamber I’ve looked at didn’t have grooves left in the freebore. If it’s a .308 groove and .3085 throat diameter why would there still be grooves left after the cut was made
If I am looking at this correctly, what I see looks pretty typical. There's one thing that confuses me, the mark on the upper land/leade, but it is most likely due to the angle of the bore scope.
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Bear with me , I appreciate all the input but am still confused why the grooves appear cut before the lands ? I just have never noticed that with other barrels , the groove always seemless and the only apparent cut or transition is on the rifling ?
There’s a 1.5 degree angle ground into the reamer at the front edge of the freebore. The lands are also “taller” than the groove. Therefore the cut of the reamer reamer is going to reach out further just like that little hump shaped cut in the groove. That little hump was what most of the posters, including me, were commenting on, because it’s the only weird thing there, but not uncommon. The anomaly that Tooley and Rubicon pointed out is weird, but could be the angle of viewing as Rubicon noted. What you’re looking at looks absolute typical.
Exactly like yours, except this barrel has a perfectly round bore. So the rear most edge of the groove appears as a mostly straight line. Look at the end of the cut on the lands though, see how the cut reaches out a little further on some of the lands? This is the same thing as what’s going on in your groove.
All be damned ! I’ve probably looked at 10 of my barrels when new and have never noticed that. Maybe at I glance I thought I was looking at the lands instead of them being the grooves ?!? Or maybe this is the first somewhat right camber I’ve got ! Who knows. I do appreciate you sticking with me though. It’s almost an optical illusion as it looks like the bullet would engage the grooves first !
The geometry definitely doesn’t jump out at you when you’re looking at that area at first. It’s much easier to perceive the actual shapes when you take the right angle mirror off the scope if you can, and view it straight on like taking the bolt out and looking into the breech with your eyeball(but obviously closer through the scope).
Without seeing all the grooves to tell if you have a bit of misalign, it appears to be a slightly nonconcentric groove circle. Which means during rifling op the groove that was cut had a bit of warble in it, little deeper on one side or the middle. If it's a 5groove barrel that is a difficult groove pattern to keep tight on concentricity (hard to measure) which is why there are few of us who attempt it. Talking very small numbers here. If each groove looks the same, that's probably the case, and you're good to go. Now go choot!
Later
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