Home Forums Hunting & Shooting Ask The Gunwriters More bore scope help, please

Working on another “problem child” rifle. A CLR/NULA that has not been as precise as I anticipated. Decided to bore scope it and have a few questions.

Pic #1
Is this hard carbon fouling?



Pic #2
Tooling marks just beyond the leade. How big of a problem is this defect?



Pics #3 -
Found these radial grooves throughout the bore. They tend to be deeper or more prominent near the chamber and less near the muzzle. How much of a problem are these and what caused them?










So, what are these defects and what impact would they have on precision? Any input would be helpful.

I’ve have other avenues to troubleshoot with the rifle, so am not set that the barrel is only problem.

Thanks

Scott

Very interesting. Just a few weeks ago I looked at the bore of my old Winchester 94/22, which I've had since the 1970s, and found a similar grove in the bore at about the midpoint of the barrel. It appears uniform in depth and extends around the entire circumference of the bore. Been wondering what caused this too.

If using a Teslong, get rid of the red(low glare) mirror as it tends to add a copper wash color in bright barrels.
Do not borescope factory rifles if you have a faint heart.

True that!

I am interested in the answer to all of your questions relating to the pics in your OP - the potential carbon ring, and the annular rings in the barrel. I have observed these in barrels of my own and figure they must be a vestige of button rifling, but I don't know for sure.

My borescope has taught me that pretty is as pretty does. These three awful looking gouges from the cut rifling process are in the bore of a 9.3x63 rebore JES did for me on a 1903 Springfield



But despite those three hickeys it does this somewhat routinely


On the other hand, I have another JES Springfield rebore, in 338-06, that looks lovely in the borescope but doesn't shoot nearly as well.

These points aren't terribly germane to the questions in your OP, but they are good to see for those who may get spooked by what they see in their borescope.

I use my Hawkeye just to verify how my cleaning of the barrel is going.

My experience resembles yours in that it will not predict how it shoots in the sense that the best looking is not necessarily the best shooting. Within reason, of course.

chamois

On pic #1, that is carbon build up. The best way I've found to remove it is with JB Bore Paste on a bronze brush. Once it's removed, that area at times can still be a bit darker...depends on the barrel material.

The stuff in the other pics aren't unusual to see in production barrels. They may or may not have any affect on accuracy....impossible to predict.

Hope this helps. -Al

A more informative test of the barrels quality would be to slug it with a soft lead slug. There’s no way of knowing what effect any of those machining defects will have on group size. A lead slug will demonstrate any dimensional differences that will definitely have a negative effect. Variation in bore diameter is the kiss of death for a rifle barrel. And yes, your barrel is badly carbon fouled.

Surprisingly, barrel internals can be a little 'loose' as long as the last 3-4" is at minimum standard to -.0002 bore/groove size. Sometimes, this is actually intentional....depending on your working relationship with the barrel maker. -Al

Al,

The worst factory barrel I've ever slugged was on a 7x57 that one of my editors could NOT get to group even three shots under 2" at 100 yards. He sent it to me, and after test-firing it a little with loads I'd found accurate in most 7x57s, I slugged the bore. It turned out the "tight" spots were .287", and there were several looser spots....

Yikes.....

All, thanks for the input and replies

Al, yes extremely helpful! I'm a newbie with the bore scope and do not have a knowledge base for barrel manufacturing. I have learned quite a bit from your responses and your other bore scope posts. I used your suggestion on for carbon fouling on my old Ruger, and it worked very well.

As some have suggested, I am going to slug the barrel to check the dimensions. I am also going to transition to low rings from Talley to improve scope alignment and work on improving my shooting mechanics. After that the focus will be on trying different bullets and powders to see what works. I have plenty of Hunter and will try the MD load. May try a low recoil 125'ish gr handload for practice.

The 7.1x57

6.9-7.1- 6.9 X 57 😊

Yep!

The editor was so discouraged that he gave the rifle to me. I had it rebarreled in .358 Winchester--because I'd always been curious how much .358 velocities could actually be "improved" in a .30-06-length action--which I doubted

My theory, of course, was based on the 4-to-1 Rule.--and it turned out I was right. It didn't gain any significant velocity....