M03 bolt problem

[M03 Fan]

First post here, and starting off with a rather odd problem.

Sometimes when I operate the bolt on my M03, and push the bolt upwards in a certain way, the bolt doesn't stop, but comes right out!  Very odd, and it doesn't always happen, but this could of course be a disaster if I'm out in the field shooting at that big moose and need to take a follow up shot.

Some videos showing the problem:

https://youtu.be/oJZo4oMe_RI

 

https://youtu.be/DD4cvMfRhec

 

https://youtu.be/cFFEYsHjpCc

 

 

Any idea what could cause this?  I'll try to contact Mauser customer support, but wanted to as here also, if anyone has any ideas.

Love the M03 by the way, it's an amazing rifle!

[Rick - Mauser M03 Blog author]

Hello M03 Fan. Good alias. 🙂

The problem you're having is a new one to me. Bit of a worry, as you say. It's not what you want to be happening when a mother moose, or a bear, or a lion has clocked your position! I just had a look at one of my M03s. My first thought is, if you look at the bolt stop lug that moves up and down in the receiver, is it moving up and down freely when you push the bolt stop button on the left of the receiver, and is the spring pushing it back up reliably? Perhaps it needs a tiny amount of gun oil on the surfaces that are in contact with the receiver? Put a little between the button and the receiver too.

Let me go and grab an M03 bolt, to look closely for any moving parts that are involved in stopping its rearward movement. Nope, no moving parts there. It's the recess under the bottom of the bolt head that meets with the bolt stop lug to stop the rearward movement. So I'm thinking there's something about the bolt stop lug or its spring that's not working correctly. Grit in between the lug and the receiver, or the button and the receiver.

Some tests to run would be:
- with the bolt removed, does the button rest at the top most limit of its movement? Does it reliably return there when manipulated? The bolt stop lug should be sticking up from the floor of the receiver.
- when you insert the bolt, without wiggling it, i.e. with the handle kept horizontal, do you need to push firmly down on the bolt stop button to get it in? I have to use the thumb nail of my left hand and push quite hard to get the button and the bolt stop lug down. I noticed from your videos that you were getting the bolt in without seeming to push the button. I think the bolt stop lug is staying down some of the time.
- when you insert the bolt, without pushing the button down with your thumb but by slowly rotating the bolt handle left and right (being careful not to ding the stock), does the button go down when the bolt head lugs apply a camming force on the bolt stop lug, and then pop back up when the bolt stop lug flicks up into the recess channel for it under the bolt body? It should do this.
- when you lower and raise the bolt handle, do you see a slight down and up movement of the button?

From watching your videos again, I'm of the view that your bolt stop lug is not moving freely. There could be grit or gunk causing friction between either the lug and the receiver, or between the button and the receiver.

Please let us know how you go. Rick.

[M03 Fan]

Rick, thank you so much for your detailed response and analysis!

Some more info:  This only happens immediately after pressing the trigger and firing (or dry-firing), it never seem to happen if I just cycle the bolt repeatedly without firing in between.  And it happens both with my .308 bolt face as well as the 375 H&H bolt face.

From the video it does appear I'm not pressing down the bolt release when inserting the bolt. I have learned from bad experience not to use my nails when pressing the bolt release (slipped and scratched the wood one time doing that), so now I always take care to press the bolt release with the back of my thumb instead.

To answer the excellent questions:

Q: - with the bolt removed, does the button rest at the top most limit of its movement? Does it reliably return there when manipulated? The bolt stop lug should be sticking up from the floor of the receiver. 

A: Yes, it rest at the top and seem to always return to the top.  See picture for how the bolt catch looks.

Q: - when you insert the bolt, without wiggling it, i.e. with the handle kept horizontal, do you need to push firmly down on the bolt stop button to get it in? I have to use the thumb nail of my left hand and push quite hard to get the button and the bolt stop lug down. I noticed from your videos that you were getting the bolt in without seeming to push the button. I think the bolt stop lug is staying down some of the time. 

A: Yes, need to press the bolt release down before inserting is possible.

Q: - when you insert the bolt, without pushing the button down with your thumb but by slowly rotating the bolt handle left and right (being careful not to ding the stock), does the button go down when the bolt head lugs apply a camming force on the bolt stop lug, and then pop back up when the bolt stop lug flicks up into the recess channel for it under the bolt body? It should do this. 

A: Yes, then the bolt release is lowered.

Q: - when you lower and raise the bolt handle, do you see a slight down and up movement of the button? 

A: Yes. Picture below of the button with the bolt raised and lowered.  The button goes down just a little when the bolt is lowered.

[Rick - Mauser M03 Blog author]

Hi M03 Fan. Thanks for the detailed responses to the suggested tests. This is getting really interesting.

I've done some investigating with my 270, along with some thinking about your point that the problem happens after you fire or dry-fire. It seems to me that something is holding or pushing the bolt catch down upon firing (I was calling it the 'blot stop lug' in earlier replies). Based on this, could you try another test please?

- cock the action and take note of the position of the button. As you've observed already, it should be almost at its topmost position. Then dry-fire the rifle (if a hole appears in the opposite wall, unload the rifle and start again). Before cycling the action, check and note the position of the button. Is it at its topmost position? If not, I'm thinking your bolt will come right out.

If the problem is indeed that the bolt catch is being interfered with, possible causes are:

- debris is getting jammed between the trigger sear and the bolt catch. The top part of the trigger sear rotates forwards upon firing and could be pushing some gunk against the bolt catch, with sufficient pressure to lower it enough so that it doesn't stop the bolt's rearward movement.

- the trigger sear spring could be broken or have slipped out of place. It could be the cause of the interference with the bolt catch.

I'm keen to hear about the results of your testing. It might be time to pull the action apart. You'll be having all the fun! Have you seen my blog post on doing this? Here's a link. How to disassemble your Mauser M03 

*****

Edit: I was also having a good look at an M03 bolt, to see if something there could be interfering with the bolt catch, after firing. I don't think it's likely, but I wonder if the firing pin nut is over-travelling and striking the bolt catch, jamming it down. I don't think so, but worth a look. I have a video on disassembling the M03 bolt, here - disassembling the Mauser M03 bolt

The firing pin nut is the bit you see sticking out of the bolt body when the bolt sleeve unit is removed. With the bolt sleeve unit removed, how far can you move the firing pin nut forward, as it would move when fired? Does it go all the way to the front of the cut-away in the bolt body, or a little short of the full length of the cut away? Mine does the latter.

[M03 Fan]

Thanks again Rick.  I think you are right - something is interfering with the bolt catch/release.

I spoke to Blaser in Texas yesterday and they said to send it in so they can have a look.  But before I do that, I'll disassemble the action to see if any debris is stuck, or perhaps it just needs a good internal cleaning. 

Will report back after disassembly and reassembly.  In the meantime, a picture from happier days with the M03 :-)

[Rick - Mauser M03 Blog author]

Good plan. You're handy with a camera I've noticed. It'd be great if you could take some pics of the insides, hopefully revealing the problem as you discover it. Mauser M03 Forensics!

I just took another look at my 270, to compare what I'm seeing in your first pic. It shows the bolt catch, the trigger sear behind it and part of the trigger sear spring, visible through the small cutaway in the trigger sear. Your trigger sear spring looks different to mine. The left-most coil is sitting away from the two coils to the right. I'll see if I can take a photo like yours. Hold on. Grrr, I'm working with my daughter's iPad mini. Posting pics is tricky. It's attached but not showing. Let me crank start the mainframe and try an Edit. Done, pic should be showing now. 

Hmmm. Well, there is a bit of difference in the appearance of your trigger sear spring vs mine, but there's not a lot in it. Worth a close look. Before disassembling, can you shine a torch down between the bolt catch and the trigger sear. Anything to see that looks out of place?

[M03 Fan]

Rick, thank you for your amazing insight into this!

I took the receiver out, and the same problem happens then of course.   It actually also happens without dry-firing:

https://www.youtube.com/watch?v=y9n_D-cTLf8

Anyway, after taking some close-ups of the bolt catch, it appears as if the front of the catch is worn.  Most likely this is why - the bolt is somehow able to sneak by on top of the worn catch.  See pictures below.  I'm shipping the receiver and bolt over to Blaser tomorrow; I'm sure they will fix it.  Will post a follow up when it's back!

[Rick - Mauser M03 Blog author]

Hmm, that first pic and the video are certainly supporting your thought that the problem could be the wear at the front of the bolt catch. Fast forward a couple of years - take a scan of the part, fire up your handy home 3D printer, insert the right cartridges for high strength steel, press 'Print' and go make a coffee. :-)

It's looking like you'll have your M03 back in business soon. Maybe even in time for some late season stalking ... . Thanks for the pics - they're a really useful resource. While your rifle is away, feel free to write up a short story to go with the snowscape pic. I could make it and the pic(s) up into a blog post, noting that it's full summer here with not much happening hunting wise. 

Regards, Rick.

[M03 Fan]

Got the repaired receiver back yesterday!   The bolt catch was welded and cut, and now sits noticeably higher in the receiver than before.  Apologies for the poor picture of the raised bolt catch.

The gun now works perfectly!   Thanks Mauser/Blaser for excellent work and quick turnaround!

The repaired bolt catch:

All parts cleaned and oiled, ready for re-assembly:

All set and ready for another hunt!

[Rick - Mauser M03 Blog author]

Great result! It'll be a handy reference in case anyone else has a similar problem with their Mauser M03 bolt coming out past the bolt catch, when pulled back during the extraction and ejection part of the cycle.

So it sounds like the gunsmith built up the top of the bolt catch with welded on metal and then machined it back to the desired shape. Good solution. Nice work. The bolt catch will ride high and snug in the bolt's groove and the bolt won't come out of the receiver until you really want it to. Just how it should be, particularly when there's bears in the woods. 

Thanks for the photos. The one showing the disassembled action is like a parts diagram. Excellent.

[M03 Fan]

Finally had a chance to go to the range and test the repaired rifle "live".  As expected, no issues.

Have to say I'm impressed with how the M03 holds zero after a barrel swap.   Due to the repair, my gun has been completely taken apart, the receiver and all metal removed from the stock, the receiver disassembled and repaired.  These are the first 10 shots after reassembly.  I just put the scope back on without any adjustments. This was for the .308 barrel.  Next week I'll go test the 375 H&H barrel (my shoulder is not looking forward to that!).

[Rick - Mauser M03 Blog author]

Wow, that is impressive holding of zero, particularly noting the total disassembly of the rifle. It echoes my own experience. With your permission I'd like to make a blog post from this story. People considering the Mauser M03 system need to see this.

Regards, Rick.

[M03 Fan]

Yes, please feel free to make a blog post of it, that would be great!  Wish I had better photos, but hopefully they are usable.

Thanks for all your help on this!

[Rick - Mauser M03 Blog author]

Thanks. I'm sure the photos will be fine. :-)

Rick.

[Rick - Mauser M03 Blog author]

Done. :-) Mauser M03 - Good Accuracy After Bolt Catch Repairs