Light Polishing Of M1A Chamber--Crazy?

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Cosmoline

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After resolving the failure to feed issues on my M1A scout, I ran into another problem last weekend. After about 100 rounds, the rifle started to fail to extract spent brass. I'd have to reset the extractor over the rim and then use the range table for leverage to knock the brass out. Nothing was wrong with the brass, and it was not overpressure. I looked a the chamber and it's ringed with ridges. I understand SOME roughness in these chambers is intentional to the design. And I understand that if you shoot it enough the failures to extract stop happening as the chamber breaks in. And I also understand that polishing a chamber much is a no-no.

But I'd like to accelerate the break-in and get rid of this annoying feature. My crazy idea is simple. Coat the sides (not shoulders) of 20 rounds of NATO standard with a little flitz, then cycle them through (not shooting) followed by a good cleaning of the chamber. I'm also thinking of mixing in some dummy once-fired rounds in there as well. I'm thinking that light abrasive will smooth the chamber a tad in the bad spots, improve reliability and at the same time not give me the mirror-polish chamber of death I'd like to avoid. Grippy, but not too grippy is what I'm after here. I'm very much leery of using any kind of drill or automatic polisher. I want the brass to do the work it wants to do.

What do you think? Be brutally honest :D
 
Back when a particular manufacturer was putting out some absolute pooh quality barrels - in finishing the chamber, execution of the gas port and muzzle crown - one of the things I had great success with (which will no doubt elicit cries of dismay from the fringe) was installing a brand new GI chamber brush on a section of flex rod and chucking that up in a variable speed drill.

Normally, I would end with lapping compound. This alone would remedy nearly all the failure to extract issues which weren't caused by the horrendous burrs found in some of the worst chambers.

Oops, forgot to address your question... I'm thinking the concept is not ridiculous but the fact that the form you'll be using (the brass) is so much softer than the chamber that your efforts will render little if any results.
 
"I looked at the chamber and it's ringed with ridges. I understand SOME roughness in these chambers is intentional to the design." Not on my M1A, or any other semi-auto weapon I've owned. You have a bad chamber, period.

Why aren't you going back to the manufacturer to fix what is obviously a quality-control problem? Since you are not having problems chambering rounds, the chamber dimensions are apparently at least minimum. Any polishing is going to make the chamber larger, depending on the depth of the ridges this could leave you with a seriously oversize chamber by the time you're done, and after you've tinkered with it the manufacturer has every right to refuse any responsibility for fixing what was originally their problem.
 
As I recall, in fitting up two Criterion barrels to M1s the last step after getting the headspace right (as per Kulek's book) was to polish the chamber with fine steel wool on a brass brush driven by a variable speed drill. But then I had been using my own finish reamer very carefully up till then, too.

If the mfr did a really lousy job in the first place I 'd see if I could embarrass them into replacing the barrel with one properly done. There really is no excuse for letting something like that out the door.
 
The ridges aren't *that* deep. They're only visible when I use a tactical light shone in from the breech.

I've attached a photo showing the marks. Do you think that's just crappy finishing? If so then it's back to Springfield.
 

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Your photo does show what appears to be some nasty tooling marks. I would call SAI, they well talk to you about this and if needed send you a shipping box and UPS label to return the rifle for service. They have a good turn around time, I sent one rifle in for a new bolt (recall), had a trigger job done while they had it and it was about two weeks total.

I've polished rough chambers before the same way your thinking. I've gone as far as screwing a brass rod into a primer pocket and using fine grinding compound on a case in a rough Brit .303 chamber.

You may want to post this question at m14firingline. Some of the best M14 smiths in the country post there every day.

Personally I would send it back to SAI, use the life time warranty.
 
That chamber certainly looks to be on the rough side. I'm not sure any polishing will resolve that, but....

Are you using, with any regularity, the M14 ratcheting chamber brush? Remember, these are not chrome lined barrels (where nothing really sticks), so a little more attentative cleaning is needed. If I neglect the chamber scrubbing I notice a lot of carbon stuck on the case necks of extracted brass. In one case the carbon buildup was the sole cause of the FTE; the extractor jumped the rim and the case was frozen in place. When I finally removed it there was a heavy carbon buildup on the neck. Have you noticed any thick carbon on the extracted casings?
 
You will find that shooting actually polishes the chamber.

I don't think a little polishing will hurt anything. Just don't be aggressive and get into the throat or oval the chamber.

Till then, lubricate your ammunition. That will reduce the friction between case and chamber and improve the function of your rifle.
 
Yup, lookin' at the photos - no way I'd tolerate it or take on correcting it myself. Those grooves will never go away without significant metal being removed and the best you'll get is the ridges (if any to go along with the grooves) will smooth some.

I'm wondering, is the chamber tight? It certainly presents as a bad/encrusted reamer in a chamber that has in fact not been finish reamed.

I'm confident SA would want it back to correct it rather than have it out there representing the company. Just looks like another "oops" in manufacturing followed by a flawed inspection... it happens.

I'd also like to see a fired case in a good photo.
 
I've polished chambers with red (fine) jeweler's rouge on a felt wheel in a hand drill. Great results. I am in agreement with the other posters that those marks are too deep to polish out. I would call SA, send them the pictures, and get their opinion. That chamber is to rough for me.
 
I contacted Springfield and they're going to take a look at it. Very excellent customer service! I received a response within two minutes of email.
 
that is great news. I am partical to Springfield Armory for that reason. If they made AR's that would be my source.
 
I understand SOME roughness in these chambers is intentional to the design.
Click to expand...
No, it actually isn't.

A M1/M14/M1A chamber should be smoother then a babys bottom.

rc
 
I thought too much polishing creates undue pressure on the bolt face.

The rep I spoke with at Springfield said they don't put a high polish on the chambers, and that it's not unusual to see those kind of marks.

Looking at the M1A forums on this issue, it appears to be pretty common for Springfield barrels to have rings left in them particularly past the lower half. Whether or not this is done on purpose I don't know. But they do appear to have caused problems with some, but not for others.
 
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FWIW, if I purchased an expensive (especially) brand new rifle and found that the chamber looks like yours, I would immediately contact them about sending it back for barrel repair/replacement. As rcmodel indicated, the chamber walls should be mirror-smooth.

O'course, I would have discovered its condition prior to firing since I completely disassemble, inspect and reassemble prior to firing any new acquisition ... milsurps got me into THAT good habit. ;)

One thing to check after getting it back: make sure that they have not simply polished the chamber into a grossly out-of-spec condition rather than replacing the barrel.

Good Luck!
 
Do you see rings on the spent brass? Either way, I think your extractor is the issue; not the chamber.

If the rims were being torn off, then I'd suspect the chamber.
 
SlamFire1, I've read for decades and decades that it's an ultimate no-no to ever put lubricant on ammo. That dramatically reduces the uber-brief grip of the chamber wall on the cartridge case at the moment of firing and allows a high force against the bolt face.
 
I wasn't about to lube the ammo. It's messy and shouldn't be necessary.

It could be the extractor, but keep in mind that while it's not yanking the rims off it's trying pretty hard to. The brass in question had some pretty good dings taken out of the rim. And this is a near new rifle that should not have weak springs. If the extractor were stronger, it might well just tear the rims off. And that's no solution.

Also, and this is the kicker, if it was a weak extractor I'd be having problems from start to finish. Instead the problem starts appearing after I've fired a few mags.

The brass does have striations in it that correspond to the chamber.

I'm pretty sure what's happening is this. As I fire, crud starts to build up in the chamber as normal. What's not normal are the machining marks. These grab bits of crudola and act to wedge it against the brass. A few pieces won't matter, but enough small bits of crud create enough friction to lock the brass pretty solid in there and defeat the extractor. Crud alone is perfectly normal, and in a smooth chamber just drops out with the brass. You never notice it. But crud lodged in a grove can't just fall out with the brass. It's locked in place--the front end fused to the cooling brass and the other end lodged in the crack. This isn't big stuff, but it doesn't have to be.

We'll see what the experts at the labs say about it. In any case I'm strongly inclined to agree that *NO* chamber on a rifle that expensive should be so sloppily finished. It's not kosher at all.
 
SF1, makes sense to me. I've mostly just neck-resized in my pet cartridges, and have accumulated so much brass that for the amount of bolt-action shooting I do, there would be little benefit. The main thing, though, is the absence of hazard from lubing. It appears to be beneficial for the semi-auto folks.
 
I'm so glad that our watchful administrator Art, addressed the lube on ammo statement. That is in fact a big a no-no. Ammunition, chambers and barrels should always be dry and free of lube. Lube will prevent the much need case sieze, and ultimately damage the firearm at the very least. I've seen lugs on bolt actions get set back by those who didn't know better. Good job Art!

GS
 
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