I just noticed this rough patch inside the barrel on a 629 never seen anything like it before. Any ideas on what can cause this?

Do you shoot lead bullets?
Can we rule out lead?

Just my guess,,but it looks like a steel rod was used to drive a stuck bullet or other bore obstruction through.
A sharp edge to the rod and if it gets off center and onto the bore itself,,,a few wacks with a hammer and you get the chatter and scrape marks.

Here's a possibility. As I understand it, the extreme heat and forces of jacketed bullets can leach out some of the chemical components of the stainless steel -- usually toward to muzzle. This phenomenon occurs more often with high powered rifles -- but I had a used Model 65 show the same sort of tiny crevices in the last half inch before the muzzle. Mine were a bit more spread out than yours, so maybe it's something else.

It was a darned accurate gun, so I did not think twice about it -- except to make sure I swabbed all solvents out of the bore after cleaning -- so I would not make it worse.

I actually just bought this gun and have not fired it or know the history of it.

I have cleaned it with solvent and brushed it several times.

Firing some jacketed bullets might smooth it.
Also could it be lead build up?

I just bought the gun so don't know the history of it tried cleaning it real good so don't think it is lead.

See how it shoots. If its accuracy is good, it's a non-issue whatever it is.

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Steve
NJ State Trooper (rtd)

On rare occasion,lead fouling left in a blued revolver barrel, goes unnoticed. [ ignored& forgotten] After some time , moisture and or caustic cleaning solvents are trapped. A little rust corrosion starts to become a pitted area. KROIL ...AFTER CLEANING AND CLEAN AGAIN. Also ,bore light inspection and clean again. PICS above look different than that ; not rust pits in SS. 629. Probably nasty lead jammed over a rough spot in the bore.

I was cleaning my M&P yesterday and noticed a similar mark towards the end of the barrel. Like Jimmy said, it was build-up. My brass brush wouldn't remove it, but a toothpick did.

I bought a new MK V in 300 weatherby a few years back and it had a "burr" about half way down the barrel, it looked very similar to yours, I only put about 200 rds through it and it shot good but it would copper foul something wicked and the ability to group would go away after 15 or 20 rds, I'm on my phone (so I can't see it that well) but I'd shoot it and see what happens, like xtrooper says, just to let you know that rifle got swapped for something else

Shoot it, if accuracy is ok, forget it. A severe cleaning with JB bore cleaner might be remove Lord knows what.

Is this an EDPM (It think that is the term) made barrel?

Looks like chatter marks to me. I suspect the rifling tool hacked out some metal on its way through. I'm sure it won't effect the way it shoots, but it will make it more difficult to clean.

How old is the gun?

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Maybe someone gouged it with a steel cleaning rod . If it was mine I'd fire lap it .

just looked on my laptop, still cant tell if some metal is missing or its something "on top of" the metal

I have an older Smith with those exact marks. Was that way when I bought it. Doesn't affect accuracy.

Just figured someone cleaned the barrel with a steel rod instead of a cleaning rod...?

Put some 0000 steel wool on a brush and start scrubbing. See what comes out.

Try a Lewis Lead Remover. They work great.

If it were near the rear of the barrel I would probably say forget about it as long as the revolver functions normally and shoots accurately, but it does look alarmingly close to the muzzle and is too deep for my liking.

I would probably start looking into a new barrel if smoothing it out proves not to be an option and you are encountering leading at that mark. Call S&W and see what their Customer Service guys have to say about it. You can email them the photos.

Chief38

Gun is going back to S&W for a re barrel, so now the long wait begins as they quoted 6 to 8 week turnaround time.

I would have shot it first... my only reason for stating this is, what if that barrel in that gun is dead on accurate and sweet shooting? what if the rebarrel takes it a step backwards? It looks like lead deposits to me (is it raised up or are those divots?), after all even a new gun has been fired before at the factory...and lead is not a quick wipe away deposit.

Like someone else stated, it probably would not effect accuracy and shooting some ball through it would likely smooth it out.

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God Bless Our Troops.

I took it to a local smith he said they are divots from pounding out a squib and basically nothing could be done. He thought the accuracy would be pretty poor but your point is well taken I could have shot the gun first. I picked it up pretty cheap so I am not to worried about the cost of the new barrel.