Ruger 10/22 Machine Gun Questions

[Spectator]

Hi there.  I am hoping and praying that someone familiar with class II mechanical operations, experienced gunsmiths, and especially anyone familiar with the TEK 10/22 design, can enlighten me.  The TEK 10/22 design is a closed bolt design invented by a former infantryman, Wayne Thorbrugh, who authored a conversion manual for the Ruger 10/22 in the mid-80’s.  This was just a wee bit before the cut-off deadline in 1986 for registration of new class II 10/22 toys.
 

Several times now, I’ve read Wayne Thorbrugh’s book, The Select Fire 10/22, a Tek 10/22 Conversion, copyrighted 1985 and published by Desert Publications.  No matter how many times I read it, I still have the same questions.  
 

 

You can read this book for free online at internetarchives.org or by downloading the pdf from a number of hosting sites.

 

I have a few questions about the fundamental design of the TEK 10/22 select fire mechanisms.  I am not aware of any contact information for the author and the publisher hasn’t responded to my request for the author’s contact information.  Thus, here I am.  If anyone has contact information for the author, feel free to message me privately.  
 

That said, here are my observations and questions regarding the class II Ruger 10/22.  Normally, in an unconverted and semi-auto state, a tiny ledge on one side of the disconnector prevents the trigger sear from any upward movement, until such time as the hammer is cocked again and thereby contacts the disconnector from up above, overcoming a small spring force and tilting/pivoting in a way that releases the trigger sear from the disconnector’s tiny ledge.

 

As I interpret this book, the author proposes 2 alternative methods for raising the position of the trigger sear, which does not rely upon the hammer or disconnector release, but rather from a contact point that is beneath the trigger sear itself.  One method involves drilling a hole into the bottom of the trigger sear, tapping it and then fitting it with a socket head screw, which would become accessible to a shooter because of an additional, elongated hole being drilled in the lower surface of the trigger’s upper, U-shaped channel.  The second method involves fashioning a small lever, then silver-soldering the lever to a 3/32 cam pin.  The book proposes a notch milled into the cam pin at 1/2 the thickness of the cam pin, after which the cam pin is inserted into the trigger through a hole drilled into the trigger (a hole hardly visible when the trigger is installed inside or the trigger housing).  
 

The author also mentions a need to mill out a radius on the trigger sear so that the trigger sear would provide space for the new and manufactured auto sear proposed in this book (a different sear from the trigger sear).  

 

Along with the hole for the socket head screw if that method is used in lieu of the lever method for select fire, that radius cut into the trigger sear is the only mandatory modification to the trigger sear I read about in this book.  An allusion is made about an additional modification that might need to be made IF there are any issues with fitting between the cam pin and the trigger sear.  If necessary, page 15 appears to offer a solution in the form of a vague proposal to remove surface area from the bottom of the trigger sear rather than increasing the depth of the already shallow notch in the cam pin (presumably in the interests of structural integrity).  That proposal appears to be the intended explanation for the illustrations at the bottom of page 15.  

 

Does everyone agree thus far?  If not, why?
 

What I do not see in this book on any page is any mention of a modification to either the disconnector or trigger sear which would disrupt the normal operation of the disconnector so as to allow either one of the select fire methods to actually function.   On the bottom of page 15, there are some detailed dimensions and an illustration of the trigger sear and disconnector, with a mere mentioning of the word modification above it.  As mentioned earlier, it seems that the purpose of that illustration and those dimensions might only relate to the cam pin fitting with the trigger sear.  If any instructions are provided on that page, I am unable to articulate the instructions for additional modifications to either the trigger sear or disconnector.  If instructions are provided elsewhere in this book for these modifications, I have likewise failed to identify them.  That is where you come in.  If instructions are provided on another page, what page would that be?  If all of the necessary instructions are already provided but I fail to articulate the instructions, can anyone please help me to understand what I am missing?  What exactly must be done to change the normal operation of the disconnector, and also allow both select fire methods to actually function?  How can either of the two select fire methods actually function, given the ledge on the disconnector, with the disconnector’s ledge contact point with the trigger sear left unmodified?

 

On page 15, some dimensions make no sense to me.  For instance, the length of the notch cut into the 3/32 cam pin does not appear to serve any purpose I presently recognize.  I believe the book said this notch was to be 0.125” in length.  The point at which the notch begins on the cam pin seems to align with the inner width of the trigger’s upper U-shaped channel, which seems to imply that the flat-facing surface of the notch is supposed to provide a place for the trigger sear to lay (until the cam pin is rotated, and the trigger sear then raises an additional 0.0465”).  However, the point at which the cam pin’s notch ends does NOT align with the other side of the trigger’s U-shaped channel (nor the other side of the trigger sear, since the trigger sear rests inside of the trigger‘s U-shaped channel).  The notch simply isn’t long enough to fully align with both sides of the trigger’s upper U-shaped channel.   The notch isn’t wide enough to allow the trigger sear to lay within the flat face of the notch in the cam pin, a cam pin that is otherwise round.  The author called for a depth of this notch to be 1/2 the thickness of the 3/32 cam pin.  0.093” is the diameter of the 3/32 cam pin.  Thus, the depth of the notch would be half as much, 0.0465”.  This notch depth dimension does not appear to be important aside.  What seems very important to me, however, is the length of the notch.  The author calls for a notch length of 0.125”.  What is the purpose of a notch length of 0.125” when the inner width of the trigger’s upper U-shaped channel, as well as the width of the trigger sear itself, is 0.25”?   What purpose is served and effectuated by the cam pin notch length being 0.125”?  If the purpose of the cam pin is to raise the trigger sear from below, and if the notch is anything less than 0.25”, then would you agree that the notch might as well not even be there and, if the notch might as well not even be there, the cam pin might as well not even be there, nor the lever to attached to it?  If I am missing something, please fill me in.  


As a side note, I have seen photographs of a couple other class II closed bolt designs for the 10/22.  One of those designs also utilizes the same lever-based, select fire mechanism.  I have not seen any close up photos of the trigger, disconnector and trigger sear separated, with the select fire lever.  I’ve inquired about the mechanism directly with this inventor and, due to the proprietary nature of his work, he did not disclose the answers I seek now, although he generously answered many other questions.  This inventor also had two other alternative select fire mechanisms, one of which was a button.  As mentioned, I have not seen actual photographs of the second inventor’s select fire mechanisms.  However, I suspect that Wayne Thorbrugh, Inventor #1 and Inventor #2 all had one thing in common: a lever-based select fire mechanism.  All 3 inventor’s designs work, although I have heard that Mr. Thorbrugh’s design is fraught with timing issues and also lacks longevity due to the reliance upon heavily used springs for bolt-arrestors.  So, it is not as though I am chasing after answers to an unproven method.  It’s proven.  
 

Thanks in advance for all consideration and insight.

[johnsonlmg41]

The TEK design is proven not to work well, that's probably all you need to know.  The mechanics of the sear and releases are all probably fine, but the reality is in that particular gun and caliber it doesn't run well.  I'll leave it at that.  So far, there is one complete overall design that works well, and that's it.  Lever or button, does not matter.

[Spectator]

I appreciate all insight.  I’m aware that the TEK design has been proven to be inferior despite the author’s insistence of going through 10,000 rounds without a so much as a blip.  I’m aware of who made a superior design and that inventor has made many designs and is quite talented.  That inventor, and the TEK inventor, had one thing in common, among other things, using a lever as a selector, silver-soldered to a cam pin with a notch cut into the cam pin.  That inventor, and a third inventor, all use the same lever selector, and the same idea of disrupting the normal operation of the disconnector.

 

It is an understanding of the mechanics of the interruption of the disconnector that I seek to understand, which is common to all designs using the lever as a selector or, in the alternative, as a second method proposed by the TEK inventor, the socket head screw.  Both the socket head screw, and the cam pin attached to the select lever, seem to be intended to function similarly in that they are supposed to lift the trigger sear.  Again, I do not understand how this can actually happen when the disconnector’s ledge locks the trigger sear down and prevents the trigger sear from upward movement.   My own guess is that the TEK author may have intended to propose removing the ledge on the disconnector, or removing the contact point on the end of the trigger sear.  But I didn’t read that in the book.  The second inventor with the superior design says that he did not modify the disconnector at all.  But he did not comment about the contact point on the end of the trigger sear.  That gives me a basis to speculate that he may have removed some material from the end of the trigger sear.  I don’t know.  I’ve never seen pictures of his trigger sear or disconnector taken apart.  I have, however, seen a picture of a third inventor’s trigger sear.  That did not include any dimensions and I was unable to determine whether material was removed from the contact point with the disconnector.  However, interestingly, that third inventor’s trigger sear had a notch cut into the bottom of the trigger sear where the select lever cam pin would contact it.  This notch made no sense to me either, since it appears that the cam pin would simply roll within the notch.  Unless, of course, that cam pin’s flat surface (milled into the half-way thickness of the pin) was positioned such that the flat surface contacted the inner notch surface, so that the cam pin would not merely roll ineffectually.  
 

Thanks in advance.  

[johnsonlmg41]

The button (screw) stays put when you pull the trigger normally.  When you pull the trigger with your finger covering the screw, it pushes up and works whatever part the lever does, but it is not locked in place like the lever, it rides up and down when needed when your finger is over it.   I have not had it apart in many years so I do not recall what moves what or how the parts interact.  Unfortunately I don't have time to take it apart these days.  I had the option back in the day and chose the button for a variety of reasons on this particular gun.  HTH

[Spectator]

Okay, after re-reading this book again, and after staring at the figure on the bottom of page 15 for the umteenth time, I am finally visualizing something that I did not see before.  What threw me off was the meaningless angle drawn into the bottom of the trigger sear, which made it look like the trigger sear came to a sharp point on one end.  If a person ignores those lines and looks at the rest of the diagram, a person can see another trigger sear modification.  However, this modification is for the select fire lever only, not to the disconnector or to the very end side of the trigger sear that contacts the disconnector.    See the two images I am including.  One image is from page 15 of the TEK manual.  The other image is a photograph that someone posted on a different forum which shows the internals of the trigger parts, EXCEPT FOR THE DISCONNECTOR unfortunately!!!!!   These trigger parts are not mine. That said, comparing the trigger sear in this photo with the trigger sear in the diagram, all of the dimensions in that diagram now make more (but not complete) sense to me.  What still doesn’t make sense to me in the diagram is the smaller diagram of an upside down “T” to the bottom and lower right of the page where it says “End View” and has a dimension of 0.075”.  I have no idea what that upside down “T” is or what it could be.   No part I’m aware of is shaped like that, unless it is a select fire lever upside down with the shaft facing up.  However, it couldn’t be that lever because the shaft of that lever is 3/32” in diameter on each end that does not contain a milled notch (3/32” is 0.093”); and even in the notch where it is milled to half it’s thickness, that would only be 0.0465” in diameter.  Any clues what that upside down T might be with the shaft  diameter of 0.075”?  Aside from this remaining mystery, I still have the greater mystery unsolved which drove me to create this thread.

 

What does make sense to me is that the diagram of the trigger sear now appears to show a notch cut out of it (if you ignore other lines).  That notch corresponds with the notch in the photograph I uploaded of someone else’s modified trigger sear.  The flat face of the notch apparently mates with the flat face of the notch in the select fire lever’s cam pin (that pin has a notch milled into it half the thickness of the cam pin’s outer diameter).  The apparent purpose of this notch is to solve the problem of the limited space for placing the cam pin lever through the trigger.  It is not possible to place the cam pin in a location on the trigger that is far enough down that the cam pin could mate with the trigger sear without “some” notch depth milled into the trigger sear.  Okay, so, that notch makes sense to me now.  The dimensions related to that notch in the diagram on the bottom of page 15 likewise makes sense, except of course of the upside down “T” labeled as “end view.”  That upside down T end view aside, I still have the original question I had when I started this thread.  
 

How is it possible to lift the trigger sear using a lever or socket head screw as a button, when the disconnector ledge locks the trigger sear in place?

 

To be specific, if you like specificity….  In the TEK design, and in the Norrell design as well (the one utilizing the select fire lever too (both inventors have one select fire method in common: the lever), how is the trigger sear or the disconnector modified from its original state to allow either the “button” (a socket head screw, called Select Fire Method #1 in the TEK book) or the “lever” (called Select Fire Method #2 in the TEK book) to lift the trigger sear using upward force applied from below the trigger sear?    Again, normally it takes downward force—applied by the cocking of the hammer against the top side of the disconnector—to release the trigger sear from the ledge of the disconnector.  That ledge is what locks the trigger sear in place.   The disconnector pivots from a hole and pivot pin located in the center of the disconnector, which is held in one position by a small spring placed in between the disconnector and trigger sear.  The disconnector is like a pivoting teeter totter, with a ledge on the very right side of the teeter totter that locks the trigger sear in place.  The cocking of the hammer presses down one end of the teeter totter, causing the other end of the teeter totter to lift; when that end of the teeter totter (with the ledge on the side) lifts upwards, the trigger sear is then released from the lower position in which it had been previously locked by the teeter totter’s (the disconnector)  ledge.  That is the normal operation for semi-auto.  Full auto must be necessarily be different.  And any select fire mechanism that would tend to lift the trigger sear from the bottom of the trigger sear (whether a lever or socket head screw) must necessarily involve an unspecified modification to either the disconnector or the trigger sear that disrupts the semi-auto operations.  Am I correct?  If not, help me to understand what my logic is flawed and why the book doesn’t omit any critical modifications.  
 

 

The member of this board, Johnsonlmg41, uploaded a photograph of what appears to be Select Fire Method #1 in the TEK design: the “button” (socket head screw).  To make use of this select fire method, a shooter applies upward force while pulling back the trigger.  Doing so lifts the trigger sear upwards, again applying upward force from below the trigger sear.  In order for this to operation to be possible, another unknown modification must be made to either the disconnector’s ledge or the end of the trigger sear that contacts the disconnector’s ledge.  The answer to this question lies within the trigger assembly of Johnsonlmg41’s 10/22 MG.  If only this kind, generous, benevolent, altruistic and auspicious man could spare some time and remove the receiver pivot pins, take pictures of how the rest of the parts are supposed to be put back together, then remove the hammer pivot pin, remove the hammer and spring, remove the trigger pivot pin and remove the trigger.  At this point, the two pivot pins in the trigger would have to be removed in order to see the disconnector and trigger sear up close.  Photographs could be taken of the disconnector including up close photos of the disconnector’s ledge end, and the end of the trigger sear that contacts the disconnector ledge end, if possible, also with the use of calipers to capture the dimensions of the disconnector and trigger sear.  If these 3 pieces (the trigger, disconnector, and trigger sear) were right before my own eyes, I would be able to see how they function together.   Without one, I can’t figure out the conceptual mechanics of this design and the question drives me crazy.  Because of the time I’ve already invested in trying to understand the design, I don’t feel I can move onto understanding something else until this chapter is closed, so to speak.  
 

 

I ran the entire book through software containing OCR (Optical Character Recognition), which made all of the words in the book “searchable,”  and I did not see the word “disconnector” appearing a single time in this book.  Isn’t that strange?  I also searched for “trigger sear” and although this word showed up I still didn’t see anything that would answer my question either.  This makes me wonder how anyone was ever able to follow the TEK manual in the first place (prior to the manufacturing cut off point, as dictated by registrations for the average civilian).  This question really irks me.  Either I am just missing something from this book, or, the book omitted a critical detail, either intentionally or accidentally.  I’ve seen some other editorial mistakes with diagrams, including a mistake on page 15 relating to the length of the notch milled into the select fire lever’s cam pin (the book called for a notch length of 0.125” when the trigger sear is 0.25” wide), which makes me suspect that the critical select fire modification information was accidentally omitted from the book either by the author or editor.  It is ironic, however, that the title of the conversion book uses the words “Select Fire” and “10/22” yet the book appears to omit the very information which would allow Select Fire Methods # 1 and #2 to function.  That omission sabotages the entire basis for the entire book.  Am I incorrect?   Or correct?  Please help me to understand, either way.  
 

Thanks in advance.
 

 

 

[Rekraps]

Woah nellie! You guys run deep... for a .22!

[johnsonlmg41]

I don't think I'm that benevolent since I have a lot of projects going on.  What I will add is that this is a trigger pack done by John Norrell and according to his manual, this design differs from the TEK design?  In the manual he refers to the TEK design as "light duty" and has/had a service of refurbish/repair to his better design.  He offered either the lever selector or the button at the time I bought this for the outrageous price of 5K.  IIRC the button was an add or vise versa?

Attached is a photo of a photo I took years ago showing the internals from the top with my notes about how it goes back together for my reference.  HTH

I have no idea why I took it apart (except I take everything apart) since it always ran fine, but I do recall there being issues putting it back together?  Could just be me, but today I do HK burst packs without issues, but that was many years ago when I did it? 

I probably have that TEK book somewhere, just because, but no idea where to find it at the moment? 

 

[Spectator]

I have seen this or similar pictures and assume that this is the Norrell design based solely upon the ball spring plunger mechanism on the top of the trigger group.  That plunger, together with the modified bolt incorporating anti-bounce weights, is a signature of the Norrell design.  
 

As far as I know, Norrell never authored a manual or book, and has no interest in doing so.  Although a couple other authors wrote books on FA 10/22’s, only Thornbrugh’s manual (dubbed the TEK design) wrote a book incorporating the select fire mechanisms that operate upon modifications to the trigger sear and trigger.  The only things in common between the TEK design, created by Thornbrugh, and the Norrell design, are the fact that each are closed bolt; each utilize the same selector lever design; each utilize a secondary selector mechanism which may also be identical; each utilizes a new auto sear. I’ve never seen the Norrell button select fire mechanism so I cannot say that Norrell’s button and the TEK sockethead screw (which you called a button) are the same thing.  I assumed you had a TEK design when I saw the sockethead screw.  If Norrell also utilized this screw as a select fire mechanism, then Thornbrugh and Norrell had one more thing in common.  Norrell once indicated that his button selector has no moving parts, is attached directly to the trigger sear, and you don’t push the button to shoot FA but rather “block” it from sticking out past the curve of the trigger when the bolt is all of the way backwards.  I suppose based upon part of that description, you could very well have a Norrell, not a TEK, design, as far as the button goes.  I’m not sure what that means about blocking the button from sticking out, unless that simply means placing one’s finger on the trigger, which would in effect block the sockethead screw from sticking out, if one’s finger was placed toward the top of the trigger’s curve.  Only you would know if you truly have a Norrell design, and you would know that as soon as you see the top of the trigger group and see the side of the bolt.  It the trigger group top has the ball spring plunger such as you see in that picture you just posted, and if your bolt had metal removed with a mill and then partially filled back in again on one side in the form of a weight, then my guess would be you have a Norrell.  As an anecdotal piece of trivia, Norrell also made a third select fire mechanism based upon how far back a shooter pulls the trigger, and he made FA 10/22’s without any select fire mechanisms at all.
 

In any case, my guess about what you actually have isn‘t relevant to my underlying question.   The second picture you supplied here, unfortunately, doesn’t answer the conceptual question of how a button-based select fire lever is able to lift the trigger sear when the unmodified disconnector ledge would prevent that from happening.  Note: According to Norrell, he didn’t modify the disconnector at all.  This means, in the Norrell design, the disconnector still has a ledge on the end that holds down the trigger sear until the hammer is cocked.  This also means that something else entirely permits the button-based select fire mechanism, or the lever-based select fire mechanism, to lift the trigger sear upwards from below the trigger sear itself (not the cocking of the hammer).  
 

Unless there is something else I am completely overlooking here, like another function of the 10/22’s original or modified FA design that allows the button or lever to lift the trigger sear, then only pictures and measurements of the trigger sear and disconnector employed in select fire 10/22’a can answer this conceptual question.  I have wondered whether Thornbrugh and Norrell intended their select fire mechanisms to work by conditioning their operations upon cocking the hammer.  That would explain the lack of any mentioning of additional modifications in the TEK book related to the disconnector or trigger sear.  However, if that were so, it seems that this would have been mentioned in the TEK book saying that both select fire methods will not work unless the bolt is pulled all of the way backwards.  Still not sure that would even work, where the disconnector is automatically forced back into a locking position by a spring located in between the disconnector and trigger sear, locking the trigger sear down.  Maybe, maybe not.  Seems mighty inconvenient even if that is the case.