How do I use a borescope properly? What are some things that are not normal for typical AR barrels?

What does a scratched up barrel look like?

What does a damaged crown look like?

What kind of fouling is normal?

How do you use a borescope when they're so goddamn annoying to rotate without any sort of bearings? And won't the metal end of a borescope scratch a barrel?

I found these little scratches on my crown. I do not know if these are normal. It's a recessed 11 degree target crown

Bore scopes will make a nats leg look like the rocky mountains.
If you don't have common sense then it's not for you.

I bought one a couple years ago.

Scared the hell out of me.

My P07 .40 barrel is down right ugly on the inside with discolored spots, spots that look like cracks, wavy lines, small amount of copper fouling, some ragged looking edges on the lands, etc., etc., etc.  And it is nearly the best shooting CZ I have.  Only the P09 9MM outshoots that P07.

Looked at other pistol barrels (FNS, M&P, etc.) and none are pretty except for an aftermarket (EFK Firedragon) .357 SIG barrel I ordered for one of the 4" FNS pistols that didn't shoot very well out of the box.  That is one beautiful looking barrel from start to finish.

You're going to see a lot of stuff that doesn't amount to a hill of beans.  How much of it is really affecting accuracy is hard to tell.

Best use I can say for one is to document a known good shooting barrel and save the pictures in a folder on your computer and date the folder/pictures so you know how old they are.  Then, if the accuracy goes south later take another look and see what changed.  Dirty?  Copper fouling?  Wear/damage in a specific area?  With the "shoots great" pictures as a base you should be able to see what changed and figure out if you can fix it (cleaning well with the right cleaners/methods) or whether wear/damage will require a new barrel.

Using a Borescope is like Googling, “why does my left toe hurt on Friday's - answer = you have cancer or you’re having a heart attack”.  The below barrel looks like it has a glass smooth bore when holding it up to a light and looking through it.  Borescope image below of that barrel.



Attached File

If it helps,  there's a channel on YouTube called "School of the American Rifle", he's an armorer who films his repairs (and teaches classes in person), and often uses a borescope, which might give you a clearer idea of what to expect to see on both good barrels and bad.  It's a great educational channel.

Give us a better picture. Close but back far enough to see the entire circumference of the barrel and crown. Straight on.
The crown. Right at the edge where it transitions from the bore to the crown should be smooth with no nicks and radiating out from the bore roughly 1/32-1/16th should be smooth. The rest does not matter. It can be more..like an 11 degree target crown or a 1/16th 90 degree step, round profile, etc
The goal is that as the projectile exits the bore. Gas escapes as evenly as possible around the entire circumference right at the point the projectile leaves space for gas to bleed by. Thus not inducing yaw one way or another.

Where the lands and grooves end and the tool bit started it’s cut for the crown..Sometimes it looks like a nick  but is not. It is just an odd angle looking at that exposed corner of the land stick out.

Sure..it could have a burr or two right there from manufacturing. If you think it might. Clean the barrel a few times to make sure the brush comes across the bore/crown a few times.