Mauser M12 Light Strikes and Bolt Disassembly

[Scotty99]

I have been having problems with my Mauser M12 (.308 calibre) giving light strikes to the primers in my ammunition, this has been happening around 1 in 5 times, withe the ammunition not firing.






In order to see if this was a problem with the firing pin I tried to disassemble the bolt.

Putting the safety in the middle position, I pushed in the little lug and turned the end of the bolt. The firing pin assembly is stuck in the bolt and will not release also I cannot turn the bolt end back into its original position as the lug underneath does not retract in the middle safety position meaning the bolt end cannot be returned to it’s original position, so it’s stuck.

Any ideas what I am doing wrong.

 

[Scottb123]

Are they mag tech primers ?

 

[Scotty99]

No they are Fiocchi. Not my normal ones, I normally use Remington but could get any last time so had to buy Fiocchi. I’ve been told they are “hard” primers and can sometimes result in misfires, although I use them in my 6mm rifle with no issues, hence me trying to disassemble the bolt to check the firing pin.

 

[Cottis]

A few years ago I (foolishly, as there was nothing wrong with it) decided to take apart the bolt on my M12. I cannot recall exactly what I did but I do remember losing skin off my fingers and having to put an insane amount of hand/grip strength in to getting it apart and putting it back together again. I have since never bothered doing it again as it all works fine. There will no doubt be a tutorial online somewhere but stick with it but walk away from it when it starts getting really frustrating/painful and go back to it later.

I'm not at home at the moment so cannot grab it to have a look and maybe pass on some wisdom (bad memories)

 

[Scottb123]

Only ask as they look like brass primers which I’ve seen mag tech have no end of fail to fires and light strikes

 

[Scotty99]

Only ask as they look like brass primers which I’ve seen mag tech have no end of fail to fires and light strikes

Yes you are right they do look like brass primers, that could be the issue.

 

[Scotty99]

A few years ago I (foolishly, as there was nothing wrong with it) decided to take apart the bolt on my M12. I cannot recall exactly what I did but I do remember losing skin off my fingers and having to put an insane amount of hand/grip strength in to getting it apart and putting it back together again. I have since never bothered doing it again as it all works fine. There will no doubt be a tutorial online somewhere but stick with it but walk away from it when it starts getting really frustrating/painful and go back to it later.

I'm not at home at the moment so cannot grab it to have a look and maybe pass on some wisdom (bad memories)

Thanks for the input. Very little online but I did find one video that says to turn the bolt shroud clockwise once the little sprung lug is depressed.

I think I have turned mine counter clockwise instead and have somehow locked it up, not able to remove the spring and firing pin nor able to turn it back again to secure it. Looks like user error.

 

[Foxyboy43]

The primers don't look too bad from the pics - how do they compare to those in fired cases?
Might just be the pic but the bolt seems to have a lot of crud in the final pic - regardless of how you sort it I would clean that out.

Hope you get it sorted.

 

[Milk no sugar please]

If I can have a stab at this, it’s not a bolt I am familiar with but I’ve seen others like it.

I believe what has happened is that by turning it counterclockwise you have effectively decocked the firing pin which would normally be reset back to cocked in the action by lifting the bolt handle as you eject a case. It won’t fit in the action as it is. Normally you would need a special tool to do this out of the action.

What you need to do is find a sturdy wooden surface, a workshop bench or maybe chopping board will do and hold the bolt so that the shroud is facing the ceiling and then catch the small amount of the end of the firing pin on the edge of the bench and push down. You will then be able to rotate the bolt body back into position and resent the cocked nature of the bolt.

This will likely chew any wooden edge a bit so don’t do it on your best kitchen work surface; when your mrs sees, it won’t be the only thing decocked today.

I’ve tried to edit your photograph to show what I mean.

 

[3595wilk]

My M12 in .243 has started to misbehave with some light strikes too.

RWS primers ...whereas Magtech work fine.....

Going to check my seating depth on my handloads.

I use an adjustable depth hand primer - so may need to see if that's had any ahem, impact.....

 

[Scotty99]

If I can have a stab at this, it’s not a bolt I am familiar with but I’ve seen others like it.

I believe what has happened is that by turning it counterclockwise you have effectively decocked the firing pin which would normally be reset back to cocked in the action by lifting the bolt handle as you eject a case. It won’t fit in the action as it is. Normally you would need a special tool to do this out of the action.

What you need to do is find a sturdy wooden surface, a workshop bench or maybe chopping board will do and hold the bolt so that the shroud is facing the ceiling and then catch the small amount of the end of the firing pin on the edge of the bench and push down. You will then be able to rotate the bolt body back into position and resent the cocked nature of the bolt.

This will likely chew any wooden edge a bit so don’t do it on your best kitchen work surface; when your mrs sees, it won’t be the only thing decocked today.

I’ve tried to edit your photograph to show what I mean. View attachment 412257

Yes it’s exactly as you describe. A lot of pressure and brute force is all that is needed to push the lower lug back and then you can rotate the shroud and remove it along with the firing pin assembly. Reassembly is the reverse with again lots of pressure and brute force.

I found this out by taking it into R&B Sporting in Ross on Wye and Rob sorted it out for me after having called Blaser/Mauser/Sauer to get some advice. Excellent service again from R&B Sporting.

There did not appear to be any issues with the firing pin assembly so it is likely the Fiocchi primers are the problem.

Also they had some Remington Large Rifle Primers in stock so I bought a load. I know for sure the Remmy ones are ok in my M12.

Thanks to everyone for their input on this.

 

[Smellydog]

The primers are not the problem, they are the symptom.
Increase the pins stroke by 0.010" or so.

 

[Scotty99]

The primers are not the problem, they are the symptom.
Increase the pins stroke by 0.010" or so.

Thanks, that might be worth doing. Any idea how I would do that?

 

[Smellydog]

Thanks, that might be worth doing. Any idea how I would do that?

Never seen the pin, put a picture up.

 

[Scotty99]

Never seen the pin, put a picture up.

I’ll put up a picture next time I’m brave enough to disassemble it again.

 

[Scotty99]

The primers don't look too bad from the pics - how do they compare to those in fired cases?
Might just be the pic but the bolt seems to have a lot of crud in the final pic - regardless of how you sort it I would clean that out.

Hope you get it sorted.

Unfortunate I’d decapped all my previous cases so nothing to compare it with.

 

[Smellydog]

There might be some crud or such down in the bottom of the bolt body.

 

[Mauser12guy]

I have opened and cleaned my M12 bolt (a decoker like yours), as others have mentioned it is not quite as easy as Mauser show. But it is ok once you get the hang of it, a LOT of pressure is needed to depress the pin while applying rotational force. Opening is the easy part, re-assembly more difficult, a block of wood helps when trying to apply pressure and make sure all parts are well lubricated, especially the release pin and parts close to it. I went from finding it almost impossible to eventually being able to repeat the operation over and over, so I suspect lubrication is the key. By the way, did you ever get to the bottom of the light strike problem? The strikes in the photo don't look too light to be honest, I would have expected them to fire.

 

[Cottis]

As an update, I keep meaning to strip my ejectors and polish them and possible the holes they protrude from as I get ejector marks on loads despite being well under pressure including all factory rounds from the past. I know they are not over pressure in any way and can see the ejectors are a touch rough and suspect there are burrs on the holes the ejectors sit in.

Anyway, finally got round to stripping the bolt today and the bolt needs to be cocked before being stripped. So whilst in the rifle, insert bolt and close but do not fire it. With the 3 position safety being on the middle setting (so safe from firing but able to remove the bolt) you should be able to just depress the small latch with barely any pressure and then rotate and the bolt will come apart. Goes back together the same way very easily. Not sure exactly what I did a few years ago but it was a very different experience.

Now just need to figure out how to get the ejectors out. Sigh! To be honest, I should just put up with false ejector marks as they are fairly light but it has always bugged me.