Bore Scope Chamber Question

[CMP70306]

Good Evening Everyone,

I recently got a bore scope and a new 6.5 PRC barrel, since I toasted my first PRC barrel in 1100 rounds I decided to take some before pictures so I could compare the wear later down the road.

However when I went to take the pictures something seemed off with the lands and grooves.

It looked like there was a gap in the cut between the groove and the land on one side while on the other both cuts looked symmetrical so I backed out to take a picture of the whole lead area.

Now this is the first new barrel I've bore scoped but something doesn't look right with this chamber. I would have expected it to be more uniform and I'm confused as to how the reamer can cut part of the grooves but leave a uncut area between there and the lands. Any ideas as to what is going on here?

 

[BillLarson]

hard to tell in the pics......looks to me like pics of the throat....
how did it shoot...???

factory barrels are notorious for bad spots..... doubt if they,d do anything..about it.....custom barrel.... i would send it back....

 

[AZShooter]

I would not shoot it. Take it back to the place where it was installed along with your borescope.

It might surprise you that the gunsmith may not have a borescope. Heck I have encountered several gunsmiths that have never looked through a bore scope! If this is the situation you might have a hard time convincing him that there is an issue. If you have another rifle with a normal chamber bring it along for comparison.

 

[CMP70306]

The barrel is a custom Savage Prefit that I bought to install myself so I have no way to take it back to the manufacture and show them in person. I have not yet shot it though that was my intention this weekend before I looked at the throat.

Most of my others have been Proof but they don't make an 18" 6.5 PRC so I went with another company instead.

 

[QuietTexan]

If it's concentric (and it's fuzzy but looks like it generally is) then that's normal.

The pictures create an optical illusion - Pic three shows the concentric reamer cut that ramps into the lands. Pics 1 and 2 show the difference in bore and groove diameter, but the poor depth of field created by essentially no lens in the borescope isn't showing the relative change in the heights of the lands so it looks like the lands aren't cut.

The reamer is cutting down two different diameters - .264 groove diameter but also .256 bore diameter, so the lands are 0.004" taller than the groove. Super high tech picture:

The unevenness on the upper left side of the 4th picture looks like there's a higher than normal spot in the barrel next to the land, which is probably a result of a wear on the button that rifled the barrel. You're cutting down a bore that is not a perfectly uniform circle but rather slightly hexagonal (because of wear on the outer radius of the button) so there should be a uniformly uncut portion along each side of the lands that gets narrower until the new major diameter is completely cutting out the grooves.

 

[CMP70306]

If it's concentric (and it's fuzzy but looks like it generally is) then that's normal.

The pictures create an optical illusion - Pic three shows the concentric reamer cut that ramps into the lands. Pics 1 and 2 show the difference in bore and groove diameter, but the poor depth of field created by essentially no lens in the borescope isn't showing the relative change in the heights of the lands so it looks like the lands aren't cut.

The reamer is cutting down two different diameters - .264 groove diameter but also .256 bore diameter, so the lands are 0.004" taller than the groove. Super high tech picture:
View attachment 332880

The unevenness on the upper left side of the 4th picture looks like there's a higher than normal spot in the barrel next to the land, which is probably a result of a wear on the button that rifled the barrel. You're cutting down a bore that is not a perfectly uniform circle but rather slightly hexagonal (because of wear on the outer radius of the button) so there should be a uniformly uncut portion along each side of the lands that gets narrower until the new major diameter is completely cutting out the grooves.

My main concern is the spot between the cut lands and the cut in the groove where it looks like nothing was cut as highlighted below.

On the other side of the barrel the cut in the grooves lines up directly with the cut in the lands which is what I would have expected.

So my question would be is this normal on a button barrel or was there an issue with the barrel or their reamer?

The main reason I'm questioning it is because my brother got a barrel from the same company after I ordered mine and the 30-06 chamber he received marked up the brass so bad it had to be reamed to .300 Win Mag to fix it. So out of an abundance of caution I wanted to ask more knowledgeable people here if this was an issue or not before I shot it.