Burr in Mosin chamber

[wallenba]

I just fired some reduced handloads in a recently acquired 91/30. The unfired brass chambered easily, but extraction took more than the usual effort. The brass exhibits a short dog-leg scratch about 1/16'' wide at about the 7 o'clock position. The chamber is full of brass flecks, so it's really hurtin' my brass. It's directly over the case web. I need help with ideas on getting this out, I've never had this before.[smilie=b:

[tomme boy]

Are you sure it is the chamber? it might be coming from the interrupter or the magazine.

[akajun]

NOt uncommon, had that issue with one of mine. Get a dremel with a flex shaft and a small cratex ball wheel. Go to the range and shoot a round off, Open the bolt slowly and before fully extracting the case mark it with a sharpie. Upon extraction, relate the scratch to the mark and that should tell you where the burr is. INsert the flex shaft throught the reciever and get to work.

[leadman]

If it is too deep to polish out with a rod and drill with fine emery on it this is what I would do.
Clean the scratch with carb cleaner or similar product. Mix up a little JB Weld and apply to the scratch. When dry sand to match the rest of the chamber. You will cause no further damage with this procedure and I have used it sucessfuly twice for this same issue.

[wallenba]

Are you sure it is the chamber? it might be coming from the interrupter or the magazine.

No, don't think that is it. I was hand feeding them into the chamber, and opening the bolt only enough to catch my brass. I did though, just double check for that with the whole box removed. I got another scrape on the fired case.

[wallenba]

Well, I made things worse this morning. Last night I put some 600 grit emery on a dowel and tried working the area in the chamber. When I tested it, I found the scratch greatly reduced. Then I noticed I had a NEW scratch, identical to the old one, at the 5 o'clock position. ??!! Not having a clue I removed the bolt head and let it set in Kroil overnight. I was going to remove the extractor to check if my headspace had anything to do with this. The extractor had a low area in the slot that appeared to be ground down a bit. A couple of taps with my brass hammer and it bent.

Anybody out there make these extractors? Numrich is out. I still have to get the old one out, hopefully in one piece.

[KCSO]

Take a BRASS case and solder it on a long rod. Coat the case with 400 grit compound and use IT to hone out the chamber. Go slow and try not to get any grit in the neck area.

[Milsurp Junkie]

I had the same issue on an M44 and resolved it with the same method that KCSO did. No more burrs. I really think it is caused by a scratch from rough rechambering of a fired steel case.

[wallenba]

Take a BRASS case and solder it on a long rod. Coat the case with 400 grit compound and use IT to hone out the chamber. Go slow and try not to get any grit in the neck area.

Great! I had a similar idea but could not figure out how to get it driven. I guess I could also just cut the neck off of the case too, just to be safe. This bore is a little fat too, so a little more room in the neck would not hurt much anyway. Looking in the chamber after hitting it with the 600, it looks too, like it might have laquer built up in there. Still...why it is scratch gouging is a bit mystifying.

P.S., I got lucky, Sarco has some extractors. I ordered a couple, along with some other 'junk' to push me over the $50 point. Free shipping then.

[tomme boy]

Be very careful on how you do this. You can really mess the chamber up. Look it over very carefully to see where it is at. Shine a flashlight in the chamber to see where it really is at. I here people sanding on the chamber all the time with these guns an have heard of just as many that they messed up.

[wallenba]

I did very little to it Tomme boy. Just a light polish. I did irreperable harm to the extractor, so I just went ahead and broke it trying to remove it. It broke off just above the dovetail, predictable. It still would not budge. I finally split it with an abrasive wheel in my Dremel tool.
I then tried my field gage--would not chamber
go gage-----chambered
no/go gage---chambered.
Evidently I'm right on the edge of acceptability. Explains why the case is blown out to the case web, and I think it's hitting the chamber mouth during extraction, leaving the mark.
I went back to Sarco and ordered a couple of bolt heads too, maybe I'll get lucky with one.

[tomme boy]

You know this chamber head spaces on the rim to the bolt face right. The chamber has nothing to do with head space. But the chamber itself can be over size. Most of the Mosins I have seen are. The only ones I have run into that are not, are the Finns. Even seen one of them that was though. You can order a couple of new bolt heads and see if that will tighten up the head space. I used to have a bunch of these for this very reason when I used to shoot these a lot. It is the same for the Enfields to adjust HS.

[JMtoolman]

The extractor is removed from the bolt head by driving it to rear. it is a tapered dove tail, so trying to drive it out the wrong way just doesn't work. Insert the extractor from the rear of the bolt head and use a flat punch to seat it even with the rear of the bolt head. Best regards, the toolman.

[wallenba]

The extractor is removed from the bolt head by driving it to rear. it is a tapered dove tail, so trying to drive it out the wrong way just doesn't work. Insert the extractor from the rear of the bolt head and use a flat punch to seat it even with the rear of the bolt head. Best regards, the toolman.

Yes, of course, done it a dozen times. But this one just refused to budge, it finally bent backwards just below the claw..

[wallenba]

You know this chamber head spaces on the rim to the bolt face right. The chamber has nothing to do with head space. But the chamber itself can be over size. Most of the Mosins I have seen are. The only ones I have run into that are not, are the Finns. Even seen one of them that was though. You can order a couple of new bolt heads and see if that will tighten up the head space. I used to have a bunch of these for this very reason when I used to shoot these a lot. It is the same for the Enfields to adjust HS.

Yes, but if it has excessive headspace, when fired the case and the bolt head moves rearward into unsupported area, and over-expands the end of the case making it difficult to extract. Enough and it will rupture there. That is how it was explained to me.
I did also order a couple of bolt heads for that reason from Sarco. (#11)

[tomme boy]

I did not see that you ordered the bolt heads, just the extractors. Anyway, the Mosin does not have a unsupported chamber. So it will not blow out at the base as you said. HS is not nearly as important on the mosin as the chamber depth is. You can have a rifle with tight HS and a loose chamber and that is worse than a gun with bad HS and a tight chamber. I had a 1942 Finn VKT that had good HS, but the chamber was a little loose. It made all of my brass have the ring all around it. Brass did not last very long in that rifle. About 4 loadings and had to throw them in the scrap bucket.

[wallenba]

[QUOTE=tomme boy;1581750]extractors. Anyway, the Mosin does not have a unsupported chamber.

You're correct. I guess a better way to describe it, is the case moves rearward to a point where the brass can expand to the point it will not stretch anymore and give out.
Anyway, I know I'm approaching that limit by what my gages told me. The field gage did not close, but it came very close. If I can get a close up I'll post a pic of what looks like what is happening.

You have to click on this in three stages to get a large pic, sorry. You can see how the bottom bulges like a coke bottle and a sharp line with the gouge (from the burr, which I believe is now gone).

[tomme boy]

Which lines are you talking about. The two vertical or the horizonal one. If that was my brass, I wold be throwing it into the scrap bucket. As much as the case is blown out, I don't think the new bolts are going to fix it. That chamber looks way over size.

[wallenba]

It's not as bad as the pics look like, but more than normal, that's for sure. The dark background on the top and light at the bottom cause reflections exagerating it. The horizontal line is probably from the burr when the bolt is rotated 1/4 turn to open. The wider deeper gouge and the smaller one were caused when extracting rearward. I can't figure out what they are hitting to do that. I will be scrapping this brass later, I'm gonna keep staring at them till I figure this out. I still think the chamber might be servicable though.
For now this problem will go on the back burner until I get some parts, I can't pull my hair out over one Mosin. I could check one of the bolts from another Mosin in it. The other extractors come out easily, so checking them would go fast enough. I need to get those 'coin type' HS gages with the notches in them, things would be easier still. These> http://www.okiegauges.com/

I'm kinda lucky that the rounds I picked to shoot were some of my reduced load cast boolits. I shudder at what a full load would have been like. Sometimes I shoot commercial ammo for the brass.

[wallenba]

I'm still waiting on Sarco to ship my order, it was made on the 8th. I made some dummies to check the action after cleaning the chamber with JB bore bright. I found that all the rounds cycled from the magazine function well and extract cleanly. I'm using a bolt from another 91/30 and obviuously, FL sized brass. However, when I hand feed them and close the bolt they often are hard to chamber and extract, and have scrapes on them. It seems as though they get pushed in a little skewed, and wedge themselves in. Examining the previously fired brass shows the brass bulge at the case web seems more pronounced on one side, just as if it were (and was) fired not concentric with the chamber. I frequently hand feed some of my loads in most of my Mosins. This has not occured before. I still have to test fire them to check this theory. None of my problems turn out to be this simple, so...

[tomme boy]

Mosins are made to feed from the mag. The rim has to slip under the extractor. Not over it. Another way to break your extractor.

[wallenba]

Mosins are made to feed from the mag. The rim has to slip under the extractor. Not over it. Another way to break your extractor.

They are pretty flexible, have not had that problem yet, but I am aware of that possibility. I would NEVER do that with my M95 Styer though!

[Molly]

It's not as bad as the pics look like, but more than normal, that's for sure. The dark background on the top and light at the bottom cause reflections exagerating it. The horizontal line is probably from the burr when the bolt is rotated 1/4 turn to open. The wider deeper gouge and the smaller one were caused when extracting rearward. I can't figure out what they are hitting to do that. I will be scrapping this brass later, I'm gonna keep staring at them till I figure this out. I still think the chamber might be servicable though.
For now this problem will go on the back burner until I get some parts, I can't pull my hair out over one Mosin. I could check one of the bolts from another Mosin in it. The other extractors come out easily, so checking them would go fast enough. I need to get those 'coin type' HS gages with the notches in them, things would be easier still. These> http://www.okiegauges.com/

I'm kinda lucky that the rounds I picked to shoot were some of my reduced load cast boolits. I shudder at what a full load would have been like. Sometimes I shoot commercial ammo for the brass.

When I grew up back in the hills, the woods were full of shade tree gunsmiths with little or no training, but a fair portion of common sense and ingenuity. They dealt with oversize chambers (such as in a 7.7 Jap rechambered to accept 30-06 cases) by simply wraping the head of the case with a bit of scotch tape between the extractor groove and the expanding portion of the case. This centered the case in the chamber, providing good ignition, and actually had a safety benefit, as the centered case was much less likely to split as a case that was laying in the bottom of the chamber and doing all the expanding on one side of the case. Believe it or not, this worked pretty well. Today, I'd take a case down to the local hobby shop and buy a length of brass tubing that just snugged up on the base. This works even better, and I've done it many times when proper cases weren't available.

Headspace was frequently a problem with some of those 'salvaged' war trophies too, but that wasn't too hard to deal with. They'd cut a washer out of 0.005" shimstock and epoxy it on the bolt face. That cured most of them fast and easily. If not, there were other shimstock thicknesses ... I don't really recomend this one, even though it worked, and I never heard of a problem with it. But I'd be nervous about the shim getting loose and lost ....

You had to watch some of them pretty closely though. A few of them were not above giving a rusty pitted bore a bright shiny finish with black shoe polish and a cotton patch ... or even with a coating of mercury, which wasn't too hard to get in those days. Most folks tended to being far-sighted, and couldn't really tell what they saw down the bore except that it was shiny.