Stuck... not sticky bolt M48

[JJ1979]

I have a 1950s Yugo M48 in 8mm mauser. I really like it but... after 3 shots of factory ammo it locks up. It is a .323 bore. I have cleaned it over the course of several weeks and used a 20 ga brush to 'polish' the chamber. Polishing allows for an extra shot. 3 (maybe 4) shots and the bolt is again stuck (as in tap/beat with a stick to open it). By the 2nd or 3rd shot the primers are pierced. I took it to a gunsmith who said it was the ammo (but I dont think they did much beyone looking at the spent cases. I tired several different brands of ammo with the same effect. the necks are pitted/rough when they do come out. I am wondering if the headspace is off as none of the serial numbers match or if the chamber/throat is f@#ked.

Any thoughts would be appreciated.

 

[BOHROK]

Sounds like it might be pitting in the chamber up by the neck. The brass is expanding into the pitting causing the very hard extraction.

 

[Potashminer]

I had a pitted case neck area in a Schultz & Larson rifle - nice old gun - had been the GrandPa's - sat in closet or somewhere for 30 plus years. Had a small number of Norma factory ammo with it. Could not open bolt on firing one - needed to "beat" on bolt handle with palm of hand to get it to open - then a struggle to extract. Polished the chamber walls - 4/0 steel wool around a cleaning brush - lots of 0W20 Mobil 1 oil to lubricate - lots of crap - much closer to shiny. But still very tight to extract a fired factory round. With bore scope found pits in neck area of the chamber, where my home made polishing thing would not go. Was finally resolved, apparently, when a "real" gunsmith pulled the barrel and somehow burnished / polished that neck area on his lathe. At least it operated closer to normal - buddy (new owner) shot a moose with it that fall, very pleased with his inheritance - but I suspect the thing is being put away for another 30 year snooze - too "pretty" to drag around in the bush...

 

[bearhunter]

Take some steel wool to the neck area of the chamber.

If it's so badly pitted, that it's transfering the indentations to the fired cases during firing, it's likely building up with carbon fouling.

Your gunsmith is likely correct about ammo, but without seeing the pitting you're describing????????

If you're shooting North American manufactured ammo, you're likely not getting much of a seal around the case when it expands during firing. That seal is very important to function as well as safety.

Mauser actions are a grab bag when it comes to function. I've literally handled and worked on thousands of them. Depending on when they were made, who they were made by or FTRed by, they can be as slick as greased glass or rough and gritty, almost like sand in the action.

The issue you describe with pitted necks, is unusual. Most M48s have excellent bores/chambers. Is the bore pitted as well???

There is something else you should check, using a flashligt/borelight.

Pull the bolt and look at the edges of the bolt lug seats in the receiver. Look for a small ridge that would indicate set back on the faces of the lug seats.

I doubt there will be anything visible and there shouldn't be if you've only been shooting factory ammo.

Still, it's possible an improperly heat treated receiver managed to get through the inspectors.

I use a dime store, dental mirror to view these surfaces. They may be quite rough as well.

The other thing you should look at is the percentage of bolt lug contact, with the lug seat faces on the receiver.

I've seen these rifles with ZERO contact on one lug and less than 50% on the other. This can be a cause of stiff or hard bolt lift after firing a few rounds.

Lapping those surfaces with valve grinding compound, starting with the lug that is making the most contact, until they're both showing at least 50+% contact is what you want to see.

I use a common felt tip, black, Sharpie to coat the rear of the bolt lug faces. Do Not disassembe the bolt to do this. You need the pressure created by cocking against the firing pin spring to get enough force on the surfaces to indicate contact.

Contact will be indicated by the amount of ink wiped off the face of the locking lugs.

M48s are some of the nicest and well made 98 style rifles on the market. They're usually trouble free.