FN Commercial Mauser problem

[spiska]

I recently purchased a nice 1952 FN commercial Mauser in 7x57. It's very clean and looks like it's been in a safe since 1960.

The bolt seemed a little sticky but I assumed it was dried oil and the chamber being a little dirty.

I cleaned it up when I got it home and it was still sticking, so I took the action out of the stock. When not it the stock, the action was smooth and not sticking.

I reassembled and the binding occurs if I torque the rear action screw to more than 15 inch-lbs, which isn't much based typical torque specs. Front screw torque didn't seem to matter.

It looks to me like the barrel channel was glass bedded. It is very smooth and matched the lines and contour of the barrel. I don't see much if any bedding material on the action or lug but the fit to the stock is clean. But I've also never bedded a stock so I could be wrong. There are steel pillars in the action screw holes that are fixed/glued in place. I don't know if this is how they came from the factory? They are a tight fit when I push the screws in. I'm used to seeing the spacers on a military Mauser, where the screws have room.

Front action screw will hit the metal pillar and tighten pretty quickly. Rear seem to have more travel to reach that point, and I don't come close to it before the binding starts.

The bottom metal and magazine also appear to be bedded to the stock, but they may just be in there tight or stuck from age and I haven't worked up the nerve to smack them any harder to see if they will come out. I don't want to damage the stock if they are bedded in by accident or on purpose. Not sure if that is normal or not.

Any issues with using light torque on that rear action screw before I take it out and see how it shoots? My best guess is maybe the bedding material in the barrel channel is resulting in pressure on the action when I tighten the rear and causing it to bind when I tighten the rear? But the bedding is forward of the front action screw so not sure that makes sense.

I don't see any stock warping side to side or tip to butt, but I'm not an expert by any means and not sure how to test for it.

Any thoughts on how to asses/fix the issue? Would a brass shim on the rear action screw potentially help? Or is light rear torque not necessarily a problem?

These may be dumb questions, but I've never really owned a rifle where the action binds like this so it's a foreign concept to me. And I really want this gun to be a good shooter and a rifle I hunt with regularly.

Thanks,

Matt

 

[spiska]

The bolt isn't dragging on the rear action screw. I did check for that.

 

[Ontario Hunter]

Look at how your magazine fits against the receiver. There should be a slight gap between the two. It sounds to me like your magazine is jammed against the receiver and when rear action screw is torqued down, the tang is bent slightly causing the bolt to drag in the track, specifically the cocking piece sear. I encountered this very issue when I dropped my 404 Mauser build into a used stock that was designed with a very thin wrist. I had to trim a very little bit of metal from sides of top of magazine box and also had to shorten the rear action screw. Ah ... look for that too. Is the rear action screw protruding through the hole into the track for cocking piece sear? Depends on what make of Mauser but this might be possible (not possible for my Springfield as the screw hole is not threaded all the way through the tang).

Also, look at the back end of the mag box. See the tab that extends up above the edges to guide cartridge rim to bolt face. Does it look shiny on top edge? That would indicate bolt is rubbing against it. This would be caused by box that is for whatever reason too short on sides. I think this unlikely but a possibility to check out.

If none of these are fixes, I suggest bedding the back end of the action and tang. Before bedding put the action back in the stock and slowly tighten the rear action screw a half turn at a time, counting turns until the bolt just starts to drag, then back off enough to free things up. That's where you want to tighten screw after bedding is added.

Try tapping lightly on top edges of the mag box with rubber hammer to see if the bottom metal can be shook loose. Hopefully. Don't beat it up.

 

[Ontario Hunter]

And finally, does your rifle have an aftermarket trigger? Timney trigger often requires some sear adjustment or the bolt will bind. Is the trigger housing gold colored? Instructions that come with Timney trigger specify shaving the sear as needed. I chose to modify the sear on cocking piece instead. Cheaper to replace it than trigger if something goes wrong.

 

[spiska]

Factory single stage trigger as far as I can tell. Doesn't appear to be aftermarket.

Magazine box looks flush on the sides when the rear screw is tightened to where it isn't binding. Maybe that's the issue then.

The tab at the rear of the magazine has some clearance and I don't see any signs of rubbing but I'll tighten it and see if the bolt drags.

Action screw doesn't appear to be high enough to impeded anything when the biding occurs.

The stock appears to be factory as best I can tell so maybe things got wonky when they bedded the barrel channel. I'll try to post some pics in a bit. I may be making assumptions that aren't correct.

Thank you for the input OH.

 

[Ontario Hunter]

So the barrel channel has been bedded end to end? Okay, not unusual for that time period. Especially for that caliber I would free float the barrel, though I don't think it will necessarily fix your problem with the bolt binding. Fix that first and then free float barrel back to chamber.

Okay, follow my instructions re half turn tightening. When the action screw reaches the bolt binding point, how does the tang look respective of stock? Is tang protruding above its stock pocket? If that is the case you should probably consider trimming the mag box a bit instead of filling the gap under the tang with bedding. It is preferable to have the tang flush with the stock. If you do trim the top of the box, you may need to shorten the rear action screw or it may either bind up if screw hole is blind ended or screw may protrude into sear channel in tang.

 

[Ontario Hunter]

What does your floorplate look like? Hinged or push-button detachable (military). It's possible someone changed the bottom metal and the new box is taller than what the stock was designed for.

 

[spiska]

It's the one where you push the button and slide it forward and the floor plate and follower come out.

 

[spiska]

Which is consistent on the FN commercial models I've seen. But I haven't seen many.

 

[rdog]

One simple test is to put a thin shim made out of a business card, punch a hole in it for the tang screw & cut it to shape put it under the rear tang & tighten it down see if that fixes the binding , in my opinion the stock spacer at the tang should not be tight in the hole & the screw not tight in the spacer.
As Ontario Hunter said the mag box should have about 2mm of clearance on top when its assembled not jammed up between the action & bottom metal.

 

[Ontario Hunter]

Hmmm. How does the bottom metal fit with the stock underneath? Is the rear of trigger guard recessed significantly below the stock? Only possible if there's no overhang with floorplate lid. If so, it may be possible to bring bottom metal out a bit flush with stock by adding bedding underneath the trigger guard at rear action screw. That would drop the box and relieve binding at top. However, I'm guessing the bottom of bottom metal is already flush with stock. If so, don't mess with bottom end.

 

[Grumpy gumpy]

Pictures would make the diagnosis easier
I would try the shim idea first before doing much else, this will let you see if the problem is there, then as OH said, check the mag well.
Gumpy