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Need help with 51M(b) reassembly

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Hi, folks.

I'm having problems getting my recently acquired 51M(b) back together. Specifically, I can't remember how the trigger/sear assembly should be installed. I thought I had paid close enough attention when I completely disassembled everything last weekend for a thorough cleaning... but apparently I did not.

I searched this forum and spent a while searching the Web, but I couldn't locate any photos of a properly assembled action. I found these pages:

http://www.box54.com/ex51m.jpg
http://www.box54.com/inst-model-50.jpg

But neither has a close up photo or drawing that will help me with this one.

Any assistance will be greatly appreciated. I'm cleaning the stock up a bit at the moment and am hoping to have some photos on my new Mossberg tomorrow or next weekend at the latest.

Cheers,

~ Greg ~
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Discussion Starter · #2 ·
Okay... I guess I should be a bit more clear. I've got the sear and the disconnector assembly installed under the receiver as it should be. I can see how the trigger pivots against the pin on the disconnector, which then moves the disconnector forward enough to release the sear. Pretty simple and neat piece of work there. What I can't figure out is the trigger spring. Which way should the loop point and where doe the L bends in the spring go?

Thanks!

~ Greg ~
 

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I don't remember if this is the same setup as the 51 since I don't have one, but sounds like it is the same sort of problem everyone has with these trigger in the stock setups....:D

Here is a couple of great pictures of a 151K posted by tfrank back last summer....:bthumb:



 

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When In Doubt!!!

:eek: When In Doubt!!! :D Take dig pics before disasembly then if ya have a glich on assembly you can reference your pics.:t :t --JMJ-- easy & free
 

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Uhhh, Soldaboat...

I don't remember if this is the same setup as the 51 since I don't have one, but sounds like it is the same sort of problem everyone has with these trigger in the stock setups....:D

Here is a couple of great pictures of a 151K posted by tfrank back last summer....:bthumb:



Uhhh, Soldaboat that is a 151M(a)!!!!:eek: Not a 151K. :rolleyes: :D Not that it makes any difference.!!!;) Dang, those have been some handy pictures haven't they!!!:D
God Bless, Frank.
 

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Discussion Starter · #8 ·
Okey-dokey... I've now got the rifle mostly assembled - the trigger spring is properly installed and I can already tell it will have a better trigger pull than when I first got it (I'm nearly certain the spring was only sitting on top of the magazing tube when I diassembled it).

The problem I'm facing now is getting the barreled action back into the stock. I've pulled the trigger enough to allow the pivot bars at the top of the trigger to engage the disconnector pin, but it seems like the magazing tube is sitting too high. As far as I can tell I've properly installed the magazine tension spring (I think that's what it's called) so the tab is facing up and engaging the slot in the bottom of the mag tube (on the underside of the feed area). The cartridge stop and stop spring are properly installed as well.

Is there a trick to getting the action back into the stock? Pretty much all of my other rifles (mostly milsurps) go back together pretty easily - just a matter of dropping the barreled action back into the stock and tightening the receiver bolts. Should the 51M(b) be just as straight-forward?

Cheers,

~ Greg ~
 

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Okey-dokey... I've now got the rifle mostly assembled - the trigger spring is properly installed and I can already tell it will have a better trigger pull than when I first got it (I'm nearly certain the spring was only sitting on top of the magazing tube when I diassembled it).

The problem I'm facing now is getting the barreled action back into the stock. I've pulled the trigger enough to allow the pivot bars at the top of the trigger to engage the disconnector pin, but it seems like the magazing tube is sitting too high. As far as I can tell I've properly installed the magazine tension spring (I think that's what it's called) so the tab is facing up and engaging the slot in the bottom of the mag tube (on the underside of the feed area). The cartridge stop and stop spring are properly installed as well.

Is there a trick to getting the action back into the stock? Pretty much all of my other rifles (mostly milsurps) go back together pretty easily - just a matter of dropping the barreled action back into the stock and tightening the receiver bolts. Should the 51M(b) be just as straight-forward?

Cheers,

~ Greg ~
Very simple solution here. Use your hand to push the barreled action into the stock, which means yes you DO have to compress the outer mag tube TENSION SPRING. (and yes that is the correct name!!!) Do as you said above
I've pulled the trigger enough to allow the pivot bars at the top of the trigger to engage the disconnector pin,
, compress the spring enough to allow the threads of the hold-down screw to engage in the "take-down stud", tighten it and you should be ready to go shooting.
As a precaution manually function test your rifle as soon as you have it fully assembled. Manually cock it and "dry fire" it, BUT dry fire it in THIS bolt position, as no damage will occur to your rifle!!!
God Bless, Frank
 

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Discussion Starter · #10 ·
Thanks for the info, Frank. I wasn't sure just how much pressure should be needed and I didn't want to risk snapping something. :)

The action went back into the stock just as you described. No problemo. The trigger works extremely well and the bolt cycles without any hitches.

The issue I'm running into now is that rounds aren't properly feeding - the cartridge cutoff isn't getting depressed enough to release a round as the bolt cycles. I removed the action from the stock with the mag tube still loaded and manually depressed the stop and the rounds (all 10 I had loaded) came flying out in about two nanoseconds. So, at least I know the tube spring is up to the task. :)

I haven't had a chance to mess with it since that point. Is it possible the cartridge stop was installed backwards? Or does it matter which way it's put back on the tube?

Also, I noticed that when the rifle's assembled the cocking knob is free to fall out of the rifle. Is it supposed to be like that? I had assumed when reassembling everything that the recoil rod (or whatever it's called) should be engaging the slot on the cocking knob to keep it in place. I didn't see any obvious problems with it and the bolt seems to be functioning perfectly fine.

Now that I'm thinking more about it, is it possible to install the bolt upside down? I have it installed with the extractor on the right side of the rifle. It fits perfectly fine without any issues and cycles just fine... but could that be a problem?

I'll have to look at it more when I get home from work this evening.

Cheers,

~ Greg ~
 

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Discussion Starter · #11 ·
Alrighty... I got the cocking knob squared away. I took it apart to see how everything fit when the bolt was out of the stock and it looks like the firing pin helps to retain the end of the recoil spring guide that goes up against the cocking knob when it's inserted. I placed the assembled bolt-end cap pieces into the receiver and the knob is now locked into place like it should be. So I can scratch that one off the list. I also made the quick determination that the bolt can only go in one way... which is what I originally thought, but it never hurts to double check when dealing with a design that's new (to me anyhow).

I still haven't figured out the feeding problem, though. Anyone have any suggestions?

Cheers,

~ Greg ~
 

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Check the locating notches...

I still haven't figured out the feeding problem, though. Anyone have any suggestions?
Cheers, ~ Greg ~

Take a look at the bottom of this 151M(a) receiver. I believe that it is the same as your 51M(b) Coneback. Notice the four small locating notches. They locate and position the outer mag tube, the one that had to be depressed in order for you to get your receiver to reach the hold-down screw. You may need to loosen the screw that holds the tension spring to the STOCK and move the outer mag tube slightly forwards, backwards, right or left to get it to align and fit into those locating notches. If the outer mag tube is not fitting INTO those notches in the bottom of your receiver then it will not be close enough to the bottom of the receiver for the cartridge cut-off to be pushed down sufficiently by the bolt to release the next cartridge. And you have a feeding problem!:rolleyes: You might also have a problem with getting the receivers hold-down stud into contact with the hold-dowd screw!!!:eek: ;) Well that could exacerbate the problem!!:rolleyes: :)
Check the alignment of the locating notches, align them as necesary and report back on what you found. If you had to loosen the STOCK's tension spring screw to align things, don't forget to retighted after everything is aligned, then double check it again to make sure it didn't shift when you retightened it!!!:rolleyes:
God Bless, Frank.
Oh and in case your wondering what I am doing to that receiver, well I am try to UNCOLLAPSE it.:eek: And I succeeded too!!!!!!!!!!!!!!:rolleyes:
 

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Discussion Starter · #13 ·
Thanks for the info, Frank. I hadn't noticed how much play there was with the tension spring and its screw when reinstalling it the first time... I was able to move it about 1/8" forward and now the rounds are coming out of the tube. Sometimes the rounds jam when feeding while manually cycling, though I'm not sure if that's because the manual cycling is slower than what it would be compared to normal operation or if it's because the mag tube is too far forward... but that's only a matter of testing and finding the sweet spot for the tension spring.

What I have noticed now, though, is that the extractor isn't working. When a round does get chambered, the extractor isn't doing its thing when I retract the bolt, leaving the round stuck in the chamber. So, I'll have to take the bolt out tonight to see if there's something wrong with the extractor.

I'll be pleased when I get this rifle functioning properly... but I'll never take it apart again. :D

Cheers,

~ Greg ~
 

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Very important...

Thanks for the info, Frank. I hadn't noticed how much play there was with the tension spring and its screw when reinstalling it the first time... I was able to move it about 1/8" forward and now the rounds are coming out of the tube. Sometimes the rounds jam when feeding while manually cycling, though I'm not sure if that's because the manual cycling is slower than what it would be compared to normal operation or if it's because the mag tube is too far forward... but that's only a matter of testing and finding the sweet spot for the tension spring.

What I have noticed now, though, is that the extractor isn't working. When a round does get chambered, the extractor isn't doing its thing when I retract the bolt, leaving the round stuck in the chamber. So, I'll have to take the bolt out tonight to see if there's something wrong with the extractor.

I'll be pleased when I get this rifle functioning properly... but I'll never take it apart again. :D

Cheers,

~ Greg ~
Very important, in fact critically important. The four little "ears" on the top of the outer mag tube MUST fit INTO the notches in the bottom of the receiver. That is if you want it to feed properly!!!:rolleyes:
Regarding the extracting problem... did you remove the extractor from the bolt , clean the gunk out of the extractor slot and the extractor spring, use a needle file to remove any displaced metal that MIGHT be restricting the extractor in its slot, deburr the extractor, and maybe even sharpen it just a little??? The extractor slot in the end of the barrel might need attention too, but I think you already mentioned that!!!
Here is how to make custom pin punches if you don't have a set of "store-bought" ones.:rolleyes:

These are nails that are used with "power drivers", you know the kind that are driven with blank shells!!! They make great pin punches!!!
The pin that retains the extractor... drive it down from the top to remove the extractor. I did all of the steps to this bolt and you can see some of the work that was done.

You can see on the left side that the extractor slot was cleaned up with a small needle file. It has the same width all the way across the depth of the slot and you can even see a small chamfer on the extractor slot. The extractor was further modified and this pic doesn't show it but the tiny flat on the end of the extractor was filed down and the underside of the extractor "claw" was filed so that there is a barely noticeable angle to it. The extractor should now tend to "dig in" and very firmly grab the rim of any cartridge. Examination of a box of fired shells shows no damage to the rim of the spent shells. There is a tiny little mark on some of the shells, barely discernable that shows where the extractor contacted the shells rim, so this mod doesn't cause a safety issue. Keep us posted!!! If you need one of those custom made pin punches, pm me with your address and I'll send you one!!!!
God Bless, Frank.
 

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Discussion Starter · #15 ·
If you need one of those custom made pin punches, pm me with your address and I'll send you one!!!!
God Bless, Frank.
Frank, you're a wealth of knowledge and I appreciate your responses more than you can imagine. :) I have quite a few punches of all different sizes, so I think I should be okay there - but your offer to send me one is tremendously appreciated.

I just got home from work and I don't think I'll be looking at the extractor this evening. I'll check it out tomorrow after mowing the lawn and will be sure to report back with what I found.

Thanks, Frank!

~ Greg ~
 

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Discussion Starter · #16 ·
So I think I've discovered the problem - the extractor claw on mine seems pretty worn:





Before removing it from the bolt I placed a cartridge against the boltface to see if the claw would hold it in place - it won't. In fact, it appears the claw isn't long enough to even grip the rim in the first place.

The extractor slot in the bolt was a bit dirty, but not enough so to keep it from functioning properly. The extractor spring seems a bit bent (in the last few coils towards the flat arm on the extractor itself) but again I don't think it was bad enough to keep the extractor from doing its thing - even when flipping the spring around the claw still didn't have the reach it needs to properly grasp the rim of the cartridge.

So, I guess I'll be putting a call in to Havlin's to see if they have this part.

Cheers,

~ Greg ~
 

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It may be possible to...

It may be possible to salvage your extractor with a little Dremel work!!!

A dremel would be the easiest way to do this but a good quality SMALL fine file should be able to do the job also.
The "A" line probably doesn't have to be done the entire length of the front part of the extractor, 3/8ths" back from the claw should be just fine.
The "B" line is drawn vertically, at least that is what I tried to do. From the perspective of the picture, use your file and move line "B" towards the barrel. On the last 3 or 4 strokes of the file lean the top of the file to the left (same perspective) so that you create a very slight hook. This should give a very slip resistant grip on the rim of any cartridge!!!
Line "C", follow it as drawn. You want to lay the angle back a little bit. Remove no metal at the bottom of the "C" line, but take 1/32" to 1/16" from the top of line "C". When all this filing is completed the profile of your extractor should be very close to the inside of the red lines drawn on your extractor. You could have it back together tonight!!!!:) And shooting it tomorrow!!!!!:D
Did you get the feeding issues resolved????
God Bless, Frank.
 

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Discussion Starter · #18 ·
When all this filing is completed the profile of your extractor should be very close to the inside of the red lines drawn on your extractor. You could have it back together tonight!!!!:) And shooting it tomorrow!!!!!:D
Did you get the feeding issues resolved????
God Bless, Frank.
I'll give it a shot with the Dremel tool. I won't be able to get to it tonight, but I should be able to perform the work sometime during the week.

As far as the feeding problem, I've not dinked with the rifle since I removed the extractor. Been a crazy-busy weekend for me, but I'm hoping to get more time to work on it this week.

I'll report back once I've had a chance to work on it some more.

Thanks, Frank!

~ Greg ~
 

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Greg...

Greg, take a close look at the 2nd pic you posted of your extractor. Its a stamped part and you can see that there is a good bit of rough edges on it. When you reprofile your extractor, debur it also. Particularly its outside edges!! Just a couple of file strokes should be all thats needed.
God Bless, Frank.
 

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Discussion Starter · #20 ·
I ended up getting a new extractor from Havlins - I needed a front sight hood anyhow, so I figured what the heck.

The rifle is now completely reassembled, it cycles fine, it feeds fine, and it extracts fine - looks like all of the issues have been resolved.

I'm taking this rifle out this afternoon for some shooting. I'll also be taking my 46B, a Lithgow No1 MkIII*, and a Finn M28/30. It will be a good day of shooting! :)

Thanks again for all the help, Frank. I'll be getting some photos of this new 51M(b) and will post them later today or tomorrow.

Cheers,

~ Greg ~
 
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