Mauser M12 Light Strikes and Bolt Disassembly

[Scotty99]

I did strip and clean my bolt but it made no difference. Sent the rifle back to Mauser and they said bolt and firing pin were fine no problem, they never explained what they did or if they did anything at all. Made up some new rounds with Remington primers, better results but still several about 1 in 5 failures. So I bought some factory ammo Sako and Federal all worked fine not a single misfire in 40 rounds an expensive test but it proved it was not the rifle but my reloads. Made up some more rounds using Remington primers again but had to use excess force on my hand primer to seat them and they wouldn’t seat properly, even though I used the RCBS primer pocket brush to clean out the pockets before priming. I think what might have been happening is that using excessive force to prime might have crushed the primer too much so it wouldn’t fire.

Anyhow factory ammo for the time being until I can get hold of a KM primer pocket uniformer to give the pockets a good clear out and get them to the same spec to see if that improves the situation.

 

[Scotty99]

It’s taken a while but I think I have solved my failure to ignite issue on my home loads. My last post above covered the issue I got having to use excessive force on my RCBS hand priming tool and the Remington primers not properly seating. Well I stripped the RCBS hand priming tool, cleaned the internal rod and spring and oiled both. Viola….it runs more smoothly and seats the primers again with that feel that you get when the primer seats correctly with just the right amount of force. Fired 26 rounds with only one misfire.

My son is sending a K-M primer pocket uniformer over the from US. Might be a bit redundant now, but I’ll use it and see if that can eliminate the 1 in 26 problem entirely.

 

[Edinburgh Rifles]

Run me through your reloading regime if you will?

To have so many misfires with many different primers is unlikely to be the primers in my opinion
We have a Sauer 100 belonging to a customer that misfires like crazy too
The bolts are massively overengineered IMO!

 

[Scotty99]

Run me through your reloading regime if you will?

To have so many misfires with many different primers is unlikely to be the primers in my opinion
We have a Sauer 100 belonging to a customer that misfires like crazy too
The bolts are massively overengineered IMO!

Briefly it’s….

Pop out used primers with Lee universal decapping die
Tumble in maize (I think) media to clean
Clean out primer pocket with RCBS wire brush pocket cleaner
Full length resize
Trim case to length 2.005” for .308 and deburr inside and out on the case mouth
Insert primer using RCBS hand priming tool
Measure powder on RCBS Powder thrower (throw slightly below target weight) and trickle up to exact weight on RCBS beam scale
Seat bullet using RCBS seating die to desired seating depth.

 

[Edinburgh Rifles]

How do you set up your FL die?
Try unscrewing it a turn and repeat
Get your brass so the bolt closes with slight pressure
Long chambers, deep primer pockets and weak firing mechanism can all add up

 

[Ronin]

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

Sorry

I’m not being an arse

But your giving advice on something that could potentially kill the end user

We don’t know if the firing pin protrusion is not within spec or indeed how far the protrusion is actually

It’s quite possible there is a piece of debris in the bolt body causing the fire control mech to stop short or be interfered with mid travel

This will cause the issue described

A weak firing pin spring will also do this

But without knowing what the factory spec of the spring rate is that is anyone’s guess


Personally

I would strip and deep clean all fire control mechanism and bolt body

Plus mage use the firing pin has obstructed travel before making any alterations

 

[Cottis]

I recently stripped and cleaned my M12 bolt (it had been a horrible length of time since it had been done, bad me)

Took it apart fully and cleaned the spring and internals of the bolt. The only thing I didn't do was take the ejectors out but they seemed fine. Plenty of crap came out. I had a couple of unexpected fail to fires and this totally rectified it. Shot over 100 rounds since without issue.

 

[Smellydog]

Sorry

I’m not being an arse

But your giving advice on something that could potentially kill the end user

We don’t know if the firing pin protrusion is not within spec or indeed how far the protrusion is actually

It’s quite possible there is a piece of debris in the bolt body causing the fire control mech to stop short or be interfered with mid travel

This will cause the issue described

A weak firing pin spring will also do this

But without knowing what the factory spec of the spring rate is that is anyone’s guess


Personally

I would strip and deep clean all fire control mechanism and bolt body

Plus mage use the firing pin has obstructed travel before making any alterations

Yes absolutely.
It's an old thread. If I remember correctly we discussed all that and the op may of done all the correct things you rightfully suggest.
I do however doubt death or injury would result from my suggestion.
There has been several rifles with the firing pin stroke to short that has had to be increased. A mere few thou is all that is needed and cleaning as you say will indeed regain such length of stroke.

None of the rifles I fixed have become dangerous. In fact one rimfire became extremely accurate after a firing pin modification.

 

[Scotty99]

How do you set up your FL die?
Try unscrewing it a turn and repeat
Get your brass so the bolt closes with slight pressure
Long chambers, deep primer pockets and weak firing mechanism can all add up

As per RCBS instruction booklet, lower press until die touches the shell holder. Pull up the press and screw in the die by a further 1/4 turn until the press just goes over slightly on the cam, to ensure the whole case is resized. Always done it this way and not had a problem until this recent issue. I’ll try your suggestion though.