How Can I SAFELY Remove Pitting From M&P Barrel?

You can't.

You would have to remove metal evenly to get below the bottom of the deepest pit.

And that will for sure change the tolerances!

rc

As far as I know, pitting is pitting and you can't "remove" it. I suppose you could clean it up and have it reblackened. Unless I don't understand your meaning.

I don't understand why anyone would "strip and polish" the barrel of an M&P.

In doing so, you would be removing the thin outer layer of Melonite-treated steel which resists corrosion. And removing too much material could alter barrel lockup and degrade accuracy.

http://www.midwayusa.com/product/150824/smith-and-wesson-barrel-s-and-w-m-and-p-9mm-luger-425

Then leave the finish on it this time.

Pale blue text is a little too personalized for me to follow.

NVM

I wonder if the marks you see are something other than pitting? Pitting is not really likely in a new barrel that has undergone that treatment... why would they even process pitted metal? Pitting comes from rust/corrosion, and that would be very unlikely in a new gun fresh from the factory -- particularly under the "finish" but not seen elsewhere on the barrel.

As you've posted above, and as I understand it, too, removing the blackened material from a melonite-treated barrel should NOT affect much of anything but it's appearance. Another name for that process, or a very similar one, is carburization. That's a surface hardening treatment (not a rust-preventative process); the black material tends to be the byproduct of the process. When it's treated, the surface has been hardened and polishing the barrel doesn't change the hardness of the metal. On some guns that use that or a similar treatment, the black surface gets scuffed pretty easily and looks like crap. (That's the case with some models of CZs, in particular.)

I have an M&P Pro, which is basically the same gun. If the pitted area you're talking about is the flat area over what we'd call the chamber (visible when the slide is closed), I think that the front and rear edges of that raised area catch the slide during the rearward and forward motion of the firing cycle, as do the rear edges of the barrel, around the chamber. Removing any metal in those areas might cause problems.

And I agree -- pale blue isn't a great color if you're really trying to communicate: not enough contrast for most eyes.

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Well removing any coating or polishing metal involves removal of some material. And that means the nose of the barrel doesn't fit in the slide bushing as accurately and that the lugs won't seat quite the same way in the slide any longer. The net result is that accuracy will suffer due to the barrel not seating as consistently in the slide any more.

Removing even MORE metal to get down to where the pits go away is just going to make this all worse.

If the pits bother you the best choice would be to cold blue the barrel so the pits are not as noticeable.

And yeah. I don't know which background scheme you're using for THR but most of us likely use the basic grey default background. The pale blue lettering is a royal pain to read against the grey. Just use basic black please.

The rest of the barrel is taken to a nice 5000 grit polish which actually helps with rust prevention.

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No. It doesn't.

And when the way that I understood what I was told when stripping my first pistol (XDM) the way the factory treats the steel with melonite the melonite bonds to the steel so even when its stripped it still has rust resistant properties from the treatment.

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Melonite (which is a form of ferritic nitrocarburizing, as is Tenifer) is a process that is meant to increase surface hardness and resist corrosion. By it's very nature, it only treats the steel to a certain depth, not all the way through. It only treats the steel to a depth of about 0.0020 in or less.

And polishing the barrels hasn't changed the accuracy or reliability at all. Even if it changed the accuracy a slight bit, the human error element would make it irrelevant. And I leave the inside of the barrel and the lug alone

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Polishing the outside of the barrel can degrade accuracy, since lockup doesn't just occur at the cam linkage, but also at the locking lug/barrel hood and anywhere the barrel contacts the slide. That said, it will not likely degrade accuracy enough to ever be noticed. However, it will certainly yield no performance increase in a quality defensive pistol.

Not trying to be a jerk here - just passing along some facts.


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BCrider said:

Well removing any coating or polishing metal involves removal of some material. And that means the nose of the barrel doesn't fit in the slide bushing as accurately and that the lugs won't seat quite the same way in the slide any longer. The net result is that accuracy will suffer due to the barrel not seating as consistently in the slide any more.

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In theory, on a tightly fitted gun set up for bullseye or target shooting, you might be correct, but I think you're assuming a level of fit between components that just isn't there for most service pistols. The typical variations between guns coming off the assembly line are probably just as great as the variations created by polishing.

In either case we're talking mere fractions (thousandths of) an inch difference when removing that blackened surface, some of which removes itself with use --- the blackened finish scrapes off with use in the areas where there's heavy metal on metal contact. If there's no contact, it's a meaningless issue.

Not every gun is a 1911. Few guns other than 1911s have removable bushings, so fitting the barrel to the bushing can't be THAT important with those guns. With many guns, the barrel bushing is not a key factor in assuring accuracy; other contact points in the lockup system assure the tightness and consistency of lockup. SIGs and CZs use other contacts points to assure consistent lockup.

I suppose you could have the barrel bead-blasted and then hard-chromed. The texture+ HC ought to hide the pitting on the breech and prevent future issues. You can then Cerakote the rest nice & pink for your wife.

I just read that by polishing to a fine grit leaves the barrel smooth and slick so moisture has no where to grab on to so it helps a barrel be a little more resistant to rust.

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Unfortunately, this also means that a thin coat of oil (which helps prevent corrosion on any firearm, regardless of finish) has nowhere to grab as well.

Re: polishing and rust.

Rust on (or in) a barrel isn't that common -- although I'm sure it can happen in the wrong environment. What is more common is rust on the frame, where it contacts the body or hand. That's one reason some folks like polymer frames for carry weapons in those harsher places.

Regular wipedowns with a CLP-type liquid or even a light coat of wax should minimize that problem. Places with high heat and high humidity present challenges...

What you are describing sounds like normal chatter marks from firing. As Walt Sherrill pointed out, while firing the barrel strikes the slide in several places once it's unlocked. For whatever reason the M&P does this more than most pistols, or at least it is more noticeable.

Remove as much rust as possible, clean it and lightly oil it (or use a coat of NuFinish) to prevent any further pitting.

Worse comes to worse, in about 200 years, the pitting will eat through the barrel and you will have to spring $70 for a brand new barrel.

If you want something for a trophy case, have the gun bronzed. In the mean time shoot the heck out of it and enjoy it.

Question: what's wrong with the default font?

If the pits are indeed from chatter marks, they will simply chatter off the next finish you put onto it. I've noticed that Sig barrels are very tight and it's normal for the coating to be worn off so the important thing to do is to simply clean and lube the barrel after each trip to the range if you are concerned with rust. You might just want to do the same with the M&P barrel.

Question: what's wrong with the default font?

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A semi-professional answer to THAT question, but not from the OP... What's wrong with the default font? Nothing.

A serif font (like the OP uses, with the small little "wings" on the letters) is supposed to help reading, and some feel they are more attractive. He's still using a serif font in message #19. (I suspect that font is the same size as the default font, but it looks SMALLER!)

For this type of application, a monitor, screen or small display on an IPAD or Smart Phone, some of the sans-serif fonts, like the one that is default here, are easier to read and actually appear LARGER than other fonts.

The OP is obviously concerned about style and making a good impression. I spent a lot of years as a technical writer, and later got into exploring how different fonts and type styles affected readability. When my work took me into computer systems, that readibility remained a concern.

While SERIF fonts are generally still considered best for printed copy, they simply don't work as well with electronic displays, where the little extra characteristics (the serifs) aren't always conveyed properly. Here's a quote from another technical source:


On top of all this, we have to understand that the eye tends to recognize words because of the word's SHAPE -- not just because all of the letters are read individually -- so some of the EXTRA stuff of the "serif" font can obscure the shape on a display. It's less an issue when printed.

If you were reading the OP's messages printed on paper, you'd probably like that font better... but here on the screen, a font like the DEFAULT font used here works better. When I was still working -- I'm now retired -- we used the VERDANA font developed by Microsoft, which seemed better than most with Windows applications and input screens.

An excellent and thorough explanation. I'm a copywriter/editor and serif fonts and wacky colors make me all stabby... at least online.

Carry on...

Why do forums allow people to change fonts?

The forums don't. It's the software the forums use. As long as you have the ability to include links and uploads, and the ability to be friendly to various flexible types of display data, you'll have that potential problem.

It hasn't been an issue on most forums -- and I dont think it's really a problem here. Being able to change some of the characteristics of displayed info is handy. It's a trade off.