Home Forums Hunting & Shooting Gunsmithing mauser hard bolt lift?

I had posted awhile back about my son getting his grandfather's vz24 7mm RM handed down to him. We were told it may have excessive headspace and just shoot factory. He gave us several boxes of factory as well as handloads he had. We had a case separate when we were shooting it the first time. It was then he remembered the factory ammo issue. After discussion here confirmed what I thought was that improper sizing created the base separating.

I sized all the once fired as minimally as I could and made some reduced loads with 4198 as well as starting loads of varget all with 120gr bullets. After shooting some the bolt lift was hard every time. Primers look good. Now the once fired brass rechambered had difficult bolt closure and opening. Factory and sized brass chambers fine. The sized brass being slightly stiffer but that is what I was going for.

Any ideas? The bolt isn't super slick to begin with at least compared to the other 270 mauser that was handed down to my younger son.

Excessive headspace does not make anything better, factory or handloads... but at least with handloads you may neck size only and the brass at least fits the chamber.

However, you may have a more serious issue in that there may be lug set-back causing the hard boltlift.

The lugs sit in helical races inside the front ring. When shot too hot the lugs can deform the races causing a low spot. When the fired case expands to fill the chamber it pushes the bolt back into the low spot.

When you cycle the bolt the lugs have a small hill to climb which is why it is hard.

Partagas;
I'm far from an expert on such things and not a trained 'smith by any means so please take that into account.

So if that rifle landed in my shop the first thing I'd do is inspect the back bearing surfaces of the bolt lugs for any signs of galling.

Sometimes as Sitka mentioned if a rifle is fed hot loads it might set the lugs back into the action. When this happens SOMETIMES one sees galling on the backs surfaces of the lugs, but not always for sure.

I'd check for function when there is no cartridge in the chamber - that is to say is it hard to lift the bolt when you are only cocking it on an empty chamber?

If so then the camming surfaces on the back of the bolt handle might be either out of alignment or the cocking piece and the bearing surface it rides on would be where I'd look.

It can't hurt anything to strip the bolt either at this point and inspect those bearing surfaces on the bolt body and the cocking piece - checking the sides of the cocking piece for signs of wear or galling.

So if all that works and looks fine, then I'd see if it functions fine with an unfired factory case - if the chamber is crooked or egged badly it can cause dragging.

If that's good, then I'd carefully inspect the fired cases and compare them to an unfired to see the difference - paying particular attention to the shoulder location and again bulges or swelling of the case.

Anyway that's where I'd start to try and diagnose what's going on with your rifle. Hopefully that was some use to you or someone out there tonight.

Good luck with your rifle and all the best to you this upcoming week.

Dwayne

wouldn't that problem exist with fired brass and new or does the once fired formed to the chamber brass force the lugs against the raceway?

Is there a way to fix this issue?

Partagas;
I am cognizant you replied to Art, but hopefully I can be forgiven if I try to respond to your query.

If the surface on the action where the back of the bolt lugs make contact with have been damaged by a too hot load setting the lugs back into the surface, then depending upon how bad the damage is it may not show up with an unfired or new case - for the reasons you said.

I'd suggest that again depending upon how bad the damage is, it might be able to be machined true by a good 'smith, but then of course it's going to mean the barrel will have to be set back accordingly and the headspace adjusted.

Hopefully that made sense?

Dwayne

As Dwayne pointed out the lugs and raceway can be smoothed up and the barrel set back a turn or two so it will be smooth...

But that will require looking very carefully at the lugs to ensure there are no incipient (or real) cracks in the metal. If they are there they will usually look like a capital letter "A" with the bottom of the lug forming the bottom of the horizontal line and the lug in the top of the "A".

98 Mauser bolts are not hard to come by...

To answer the first question it looks like you understand exactly where the potential problem is and you are correct. The brass does not expand to fit the chamber until after firing.

Any idea how much a Smith would charge to fix this issue? I don't want to dump a lot of money into it as a serviceable 700 or how a etc. Could be bought for reasonable but it is somewhat of an heirloom or has sentimental value so I am wanting to get it fixed but not go crazy with it.

I converted a VZ24 to 7mmRemMag and later fired a shot that Quickload thought was 107 kpsi. The bolt got fatter behind the lug and the abutments got narrower. The bolt would not move much. I put some valve grind compound on the side of the bolt body and the inside of the abutments and worked it. Later I shot animals at very long range with it.

That might not be your problem. You might have dented abutments if there is only hard bolt lift after firing, but even after firing wimpy loads. That would require grinding compound between the bearing surfaces of the bolt lug [the rear] and the abutments [front]. You could make a spring loaded cartridge for lapping, or just pull the right way on the bolt handle.