Borescope results?

cdhknives

cdhknives

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I am trying out a new borescope and need help understanding what I am seeing vs what is realistic to expect in the bore of a new barrel blank. If you paid for a midrange ($250-300) manufacturer's hand lapped barrel blank would you expect to find occasional reamer marks still present? How much is too much? Also, one of the tops of the rifling lands is frosty for about 4" near the muzzle, like it was a bit short and didn't get lapped.

Also, when turned between centers it has .009" of bow from high to low in the center of the barrel. Normal or unacceptable? #2 contour, so fairly thin but not featherweight.

I will add that this is my second barrel from this maker and the first shoots about 1.25 MOA and has similar bore finish. I don't want to spend the time to thread and chamber this one if it is also going to be similarly average. My first barrel was a Green Mountain unturned blank and while the bore is less 'clean' I turned it to a light varmint contour and it registers near zero deflection in the middle when turned between centers, and it shoots about MOA for a third the price.

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Frosty land next to lapped one
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I have no experience with borescopes and NEW barrels. I have used one to view the throat of used barrels to gauge age and condition.

My original hunting rifle, given to me by my Dad in 1970, was a 264 Win Mag in a 1960 vintage Winchester Model 70. Lucky me, oh my!
I learned to reload on this rifle. I never loaded it for 'factory' velocities, because that was tough since you couldn't buy the bore riding bullet the factory had. I recognized the short throat or leade at the beginning of my time with this fine machine. Never ran the thing hot, EVER.
I estimate total rounds thru the rifle at less than 2k, and I have confidence and evidence.

At least a few hundred rounds ago, I noticed the group opening up. Lengthy cleanings sessions would change things, but not much or for long.
I borrowed a borescope from a friend, and looked at all the rifles in my fleet, and several others. I never fully appreciated how 'consumable' barrels are, especially in the hot bottleneck calibers.

The erosion is easy to see, once you have seen it.
 
I think that's what you should expect from a factory production barrel. Advance marks in the throat are common, same with the chip drag in the groove you pictured. It's hunting grade. I'd sh*t pants over any of those blems in a match barrel from a wait listed manufacturer, though. With careful load length setting and powder charge testing, there's no reason that barrel couldn't shoot under 1" after a good break-in. Of course, an equally spec'd match barrel would half that from day one, even with sloppy loads. It all depends on your expectations and budget. Where did that one come from? Was it factory chambered, or 3rd party?
 
Not a factory barrel...a custom aftermarket bbl blank. Not naming them yet. $250-300 price range for just the profiled barrel blank.
 
Not going to drag a 'name' through the mud just yet. Suffice it to say a significant step above Green Mountain class aftermarket barrels but likely below Bartlein, for example. The price range and the 'hand lapped premium' promise along with a known name that has been around for decades is all I'll say for now.

To be clear right now it is a unmodified, profiled blank I am considering returning. Would you accept a blank out of the shipping tube like that for $300???
 
Last edited:
westerner said:
I have no experience with borescopes and NEW barrels. I have used one to view the throat of used barrels to gauge age and condition.

My original hunting rifle, given to me by my Dad in 1970, was a 264 Win Mag in a 1960 vintage Winchester Model 70. Lucky me, oh my!
I learned to reload on this rifle. I never loaded it for 'factory' velocities, because that was tough since you couldn't buy the bore riding bullet the factory had. I recognized the short throat or leade at the beginning of my time with this fine machine. Never ran the thing hot, EVER.
I estimate total rounds thru the rifle at less than 2k, and I have confidence and evidence.

At least a few hundred rounds ago, I noticed the group opening up. Lengthy cleanings sessions would change things, but not much or for long.
I borrowed a borescope from a friend, and looked at all the rifles in my fleet, and several others. I never fully appreciated how 'consumable' barrels are, especially in the hot bottleneck calibers.

The erosion is easy to see, once you have seen it.
Click to expand...
Yeah, getting a borescope has been...enlightening. Previously I was trying to diagnose why my second try at barreling a rifle has performed so average, so I bought the scope to check it out. I also bought another barrel (#3) for a different rifle, decided to look down it, and it looks just like #2 less 300 rounds of erosion and cracking from a 6.5PRC. So maybe this is normal? It is certainly smoother than the barrels in my factory rifles and AR's. 'Railroad tracks' comes to mind in a few of those, but they are not $300+ barrels either.

So I ask the experts here...what is reasonable to expect.
 
I've been scoping barrels for about 8 years. GA Precision (not sure if they are making their own or buying), Shilen, Daniel Defense and many others. That barrel looks very average to me. And by average, I don't mean high end average. My Savage Model 10 barrel looks at least that good and it's a production line barrel (and it shoots bugholes).
 
This is the second barrel I have bought from these guys. I didn't have the borescope for the first but did notice that the first wasn't straight.....008" bow on that one, .009" on this one. Comparing them now that I have the scope they have similar machining marks inside but I haven't had the opportunity to look down really high end barrels.

I guess I can name them. The pics are from a brand new unfired/unchambered 6mm SS Shilen blank bought through Midway. My other is a 6.5mm cromoly blank I bought direct from Shilen and it has both substantial erosion after only 300 rounds but very average accuracy and similar machining marks inside...and it coppers up terribly. Worse than any of my factory rifles. I really thought at this price level the interior quality would be better and have to decide to proceed or return before I start making chips on this one I just received...
 
9 thou bore misalignment isn't bad. Just clock the barrel straight up or down.

The makers tooling definitely chattered there. Never seen that in any of the barrels I have used.
 
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