Gunsmithing Chamber/lands damage?

[ToddM]

Just thought I'd see if some of the barrel experts have seen something like this before, and what might cause it. I'm new to the bore scope thing so I know things can look worse than they are, but I see two concerning things here compared to other barrels I've looked at, that may or may not be. The first is that it appears there are "ridges" or grooves (going from top to bottom) in the chamber as it approaches the lands. The second is that the start of the lands appear rotationally "Smooshed' also going from top to bottom. Where the top of the land is fairly sharp/clean and the bottom of the land has been "smooshed" downward. All of the lands display similar deformation.

Thanks in advance,

Todd

 

[...]

.....hows the gun shooting?.....

if its shooting fine...dont worry about it.

if its shooting like shit, try recutting the chamber.

the problem with borescopes is you see everything in the barrel......and 95% of the "imperfections" you so have 0 bearing on the performance.

 

[ToddM]

Honestly not horribly, it replaced a factory barrel that shot pretty darn well, and it shoots about the same as that. I expected it to shoot better, and was always a bit disappointed in it, but figured it was just me or I had not found the right ammo etc. Recently I bought a borescope and was pretty surprised I saw the above compared to other factory/custom barrels I have. It's certainly not shooting shotgun patterns, I'm just more curious as to what would cause such "damage".

 

[ShtrRdy]

Are you using a Hawkeye borescope or something else?

 

[m1match]

It almost looks like your chamber reamer was dull. I've looked at my barrels (Bartlein, Rock Creek, AI, White Oak) with a Lyman borescope and the throats on them look cleanly cut. Yours look like the beginning of the rifling was distorted by the chamber reamer and the transition from chamber to throat is not cut cleanly. Who chambered your barrel?

 

[Supersubes]

Wow, what a shit show! The leade angle looks really steep, and the wavy pattern in the freebore is weird too. I can’t imagine a reamer cutting that badly. I’d expect the wiped burr off the leade to have broken off during firing. Looks like everything went wrong there...

Did you buy this new? Was it a prefit, or a smith turned a blank for you? That’s just terrible looking.

 

[ToddM]

It's a Lyman borescope, the pictures on the screen are a bit better than the images it saves off, my guess is just because it's hard to hold it steady and press the capture button, hard to complain for under $170 though.

It's a custom pre-fit barrel by a well known company, I believe they use Shilen blanks. I bought it new a couple years ago, haven't shot it too much and at the time I never had a borescope. Tried a few types of ammo, it shot well but really no better than the factory barrel. However, I mostly shoot it off hand so either barrel outshoots me.

I did return it to them a couple months ago, they test fired it, stated it performed within their standards, and as such it was not a candidate for replacement, which is hard to argue with. My impression on the phone with them was they were avoiding discussing the damage or it's possible cause and they didn't seem concerned by it. It's being returned with a test target listing the ammo they used to test it. I haven't seen it yet, so I don't know what the test target will show, and I didn't think to ask what their standard was for range/group size to pass their test, but perhaps the target/report will say.

I'm just curious in the cause, even reviewing lots of various pictures of types of chamber/rifling damage I didn't really see anything like it. I could see a dull reamer doing the "smooshing" of the lands, but what caused that wavy pattern in the freebore is what intrigues me the most. However I know next to nothing about chamber reaming so I figured I'd ask here we might have someone that has seen something similar.

 

[MarinePMI]

Looks like a rough chamber job with a dull reamer to me...

 

[DAVETOOLEY]

Not good. I've seen worse a lot worse. CNC's are great for making parts but they can also produce a lot of substandard chambers if you're not careful. One solution is to go in with a throating reamer and clean it up or set the barrel back a bit and rechamber.

 

[noisewaterphd]

I've seen lots of prefits from many different makers that look just like that. Most of the time they will still shoot, if not then DAVETOOLEY is right on the money for solutions.

 

[Terry Cross]

Even if this barrel shoots really well, I would encourage you to clean regularly with a decent solvent to help manage the carbon.

I absolutely HATE cleaning and am a big proponent of less is better when it comes to bores. My concern is with the lead preceding the actual throat. Like Supersubes mentioned, the "wavey" marks are peculiar A.F. I would imagine that those wave patterns are going to do an exceptional job of catching and accumulating carbon right where it can cause issues.

2nd concern would be with the trailing edge of that land. It is going to tear and form the bullet jacket in a manner that will impede the best seal for the rest of the trip down the track of that land/groove juncture. If that is actually a thing, you could expect some very uneven throat erosion biased toward that side.

You didn't mention caliber but smaller bores like .224 and 6mm'ish will be more prone to all concerns above.

Most pre-fits that are in the lower price range are there for a reason, so I wouldn't beat it down too bad as long as it reasonably performs. I agree with most of what was already said above. You could probably be best served by just shooting and cleaning it as long as it is putting bullets in a predictable path.

Good luck with it.
If you have any notable updates later about it shooting crazy good or coming totally off the track please update the thread.

.

 

[ToddM]

It's a .22 LR barrel for a S&W 41 pistol, so a setback unfortunately isn't possible. At about $350 it's not really expensive, especially compared to custom centerfire barrels, but for a .22 barrel not cheap either. Normally I don't clean my .22's until they start showing issues, but I can see where this chamber/throat could hold a lot more carbon than normal. I wonder if it might also explain why the chamber seems to foul (causing extraction issues) quite a bit faster than I'm used to even in other target barrels. I wrote it off as probably just being a very tight target chamber, but perhaps it's also getting more blow back pushed back into the chamber as well.

I'll keep shooting it as long as it performs reasonably and step up my normal .22 cleaning routine.

 

[hangunnr]

If that were my barrel and I was set on keeping it I would have it re-lined.

Basic process can be seen HERE if you’re not familiar with what’s involved.

 

[MarinePMI]

No offense intended, but no, barrel relining is probably not the best route IMHO. Lining a barrel is usually done when 1.) the barrel can't be easily removed (pinned/press fit barrels), or 2.) the owner wants to retain the original barrel (whether for looks or for practicality).

If a barrel can be unthreaded, either it needs to be replaced, or as mentioned above, needs to be set back and re-chambered. Could it be relined? Sure. But why would you? The problem here is the chamber, not the rifling.

 

[hangunnr]

No offense taken but did you see where he stated it’s a S&W model 41. Don’t think you can unscrew one of those barrels.

 

[natdscott]

Could it be relined? Sure. But why would you?

2.) the owner wants to retain the original barrel (whether for looks or for practicality).

I reversed a couple things and deleted some things, so that you can see the answer to your questions.

He may very well be in that position. There are some 41s that exist that are damned desirable.

 

[MarinePMI]

natdscott & handgunr,

Yeah, I missed that reference to it being a S&W 41 (my bad). I am wondering how his smith replaced the barrel though...

 

[Supersubes]

It's a .22 LR barrel for a S&W 41 pistol, so a setback unfortunately isn't possible. At about $350 it's not really expensive, especially compared to custom centerfire barrels, but for a .22 barrel not cheap either. Normally I don't clean my .22's until they start showing issues, but I can see where this chamber/throat could hold a lot more carbon than normal. I wonder if it might also explain why the chamber seems to foul (causing extraction issues) quite a bit faster than I'm used to even in other target barrels. I wrote it off as probably just being a very tight target chamber, but perhaps it's also getting more blow back pushed back into the chamber as well.

I'll keep shooting it as long as it performs reasonably and step up my normal .22 cleaning routine.

What does the rest of the chamber look like? This reamer was doing a really bad job of cutting, and I’d guess things are probably undersized because of that. Not surprising it doesn’t extract well, or fouls up. 22’s are low pressure so the case might not show much, but what does the fired brass look like? Now that we know it’s a 22lr, I’m even more shocked it came out so ugly. So little material gets removed in a 22lr chamber job.

I wouldn’t stand for that kind of work for a second, and I’d get pretty assertive about a replacement or a refund. If I sold a job like that to somebody, I’d be fucking embarrassed!

 

[ToddM]

It's a good question, one I honestly don't know the answer to. The the whole barrel "assembly" (which is how it comes as purchased) is one piece. From what I've seen on other forums they are using a Shilen blank large enough to machine down to the finished product. I have no idea if they are doing all the machining, chambering etc. or if they are outsourcing it.

So it's really one piece, but there's no way to set it back, or replace just a threaded "barrel" portion, but it could be sleeved. Which isn't that uncommon for high end target .22's and would probably be around $200. Might be an option should this one start to go south, as I do like the balance.

 

[ToddM]

Looks like I'll have to call them again tomorrow, when I talked to them 3 weeks ago it sounded like they were packing it up to ship back, haven't seen anything yet.

 

[hangunnr]

Did you get her back yet?

 

[ToddM]

Actually it arrived back Saturday. When I called them I was told their computers were down for 1.5 weeks so nothing shipped out during that time. I can say it was not packaged very well just rolled in bubble wrap with the ends not covered, so when I opened it the front of the barrel was hitting the box, thankfully it didn't go through the box and get lost/damaged. I was not charged for the testing/ammo/return shipping. They didn't mention the barrel/chamber damage at all, only that it passed their testing standard of the X-ring (1 5/8" at 50) so it did not require any service/replacement.

They returned it with a test target with five 10 shot groups, and it's very hard to argue with the results. They used a machine rest just for the barrel and it must be indoors because it noted that it was climate controlled. At 50 yards all of them are under 1" outside to outside with Eley Match black box (groups below, squares are 1"). On average I'd say center to center all 5 groups are around 5/8-3/4" and they did state it performed about "average" of their barrels tested. Though one has to wonder how good it would shoot without the chamber damage.

I have mixed feelings about it. I'm surprised they had no idea as to what could have caused the damage, and they didn't really want to discuss it. I just figured that a shop that chambered thousands of barrels, and no doubt removed/inspected tons of factory barrels would have an very good idea about what causes pretty much any type of chamber/rifling damage over the years.

At the end of the day, it shoots way better than I ever could, but certainly something went very wrong in the chambering process, and you have to wonder how well it might shoot if it didn't have the chamber damage. There's also the points others have brought up about long term issues such as uneven throat erosion, faster accuracy fall off between cleanings, faster chamber fowling causing cycling issues etc. At this point I'll likely just shoot it and make sure I clean it more frequently than I normally would a .22 barrel. While I was not overly impressed with the issues trying to contact them, get responses, return packaging, etc. I was not treated with disrespect, no one was rude to me etc. I doubt I'd purchase from them again, but I also won't go out of my way to bad mouth them either.