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SELECT FIRE 

10/22 



By Wayne Thornbrugh 




The TEK Full Auto Conversion 



229 



SELECT FIRE 

10/22 

By Wayne Thornbrugh 




W ft 
The TEK Full Auto Conversion 




Desert Publications 

El Dorado, AR 71731-1751 



I 



Select Fire 
10/22 

By Wayne Thornbrugh 



©1985 by Desert Publications 
P.O. Box 1751 
El Dorado, AR 71731 
501-862-2077 



ISBN #:0-87947-229-4 

109876543 

Desert Publication is a division of 
The DELTA GROUP, Ltd. 
Direct all inquires & orders to the above address. 

All rights reserved. Except of use in a review, no portion of this book 
may be reproduced by any means known or unknown without the 
expressed written permission of the publisher. 

Neither the author nor the publisher assumes any responsibility for the 
use or misuse of the information contained in this book. 



ii 



Table Of Contents 



Foreword 1 

Which Configuration Is Best, The Front 

Mounted Bolt Arrest or Or The Rear? 3 

Fitting The Auto-Sear Trip Tolerance 5 

Full Auto Operation— Rear Mounted Arrestor 17 

Fitting Rear Arrestor To Bolt Clearance 23 

Fitting Front Mounted Arrestor To Bolt Clearance 33 



111 



WARNING 



Since the Hughes' Amendment, which went into effect on 
May 1 9, 1 986, it is no longer possible for civilians to do Form 1 
conversions or manufacturing of machine guns. Also, Class II 
manufacturers can no longer produce machine guns for 
civilian consumption. 

This book is produced and sold for academic purposes only. 
Since the original text of this book was written before the 
above date, some of the text may be interpreted otherwise. 

Let this warning emphasize that the actual production of a 
machine gun by a civilian would be in violation of Federal Law! 



IV 



FOREWORD 



The designs offered herein are not the brain- 
child of a great gun designer but the stubborn 
persistence of a retired military ordnance man 
who undertook the project simply because they 
said it couldn't be done. The project developed 
into a small Class II manufacturing business 
which sold the converted 10/22's in most of the 
states where they are legal to own. To date, after 
at least 100 thousand rounds fired, we have yet 
to have a parts failure, Ruger's or our own. 

After the final development of the first three 
prototypes, we started a record of rounds fired, 
which gun and what ammunition. After thirty 
thousand rounds we quit keeping records 
because all major brands seemed to work 
equally well except for residue, grease and wax. 
C.C.I, ammunition seems to burn cleaner and 
leave less residue than all the others. So, for that 
reason we must recommend their product. 

Hardly a day goes by that we do not receive a 
letter or phone call from someone who wants to 
roll their own. In our supply / demand economy 
someone will usually step forward to fill a void 
sensed by the public. 1 believe this book will fill 
that void, otherwise, neither the publisher nor I 
would have undertaken the task. We both hope 
you concur. 



It is not difficult to design a drop-in automatic 
sear, to trip it and bypass the trigger sear to 
allow the 10/22 to, theoretically, cycle auto- 
matically. Many hobbyists, gunsmiths and 
Class II manufacturers have attempted to 
convert the Ruger 10/22 to closed bolt, select 
fire since 1 964, when Bill Ruger placed it on the 
market. None, to my knowledge, have worked 
with any degree of reliability. Most have not 
and will not work, period! 

The first step towards solving any problem is 
recognizing the fact that there is one and what it 
is! The answer to converting the 10/ 22 to select 
fire is solving the problem of bolt bounce. In 
counter-recoil the 10/22 bolt will bounce 
upwards of 3/ 16" after striking the breech face 
of the barrel. This allows the hammer to expend 
its energy on the bolt rather than the firing pin. 

With the bolt just .025 out of battery, the bolt 
will block the hammer from the firing pin due to 
the angle of attack. This is, in reality, a safety 
feature as well as a method to prevent easy 
conversion of the gun to slam fire. Bill Ruger 
knew exactly what he was doing when he 
designed the 10/22. 

Plans, and in some cases parts, have been 
available to convert the 10/ 22 to closed bolt, 



1 



SELECT FIRE 10/22 



select fire, but by and large they have over- 
looked the problem of bolt bounce or con- 
veniently ignored it for the sake of commerce. 
Others have given up on a closed bolt system 
and designed elaborate open bolt systems. 

An open bolt system for the .22 rimfire 
cartridge in any configuration is unsatisfactory 
simply because the cartridge case does not lend 
itself for an open bolt mode. In the open bolt 
mode the firing pin must precede the bolt, be it 
fixed or pivoted. This allows the firing pin to 
make contact with the rim of the case which 
holds the priming mixture before the bolt is 
fully closed and any way you cut it, this 
amounts to headspace— excessive headspace. 
This is why you get all those ruptured cases and 
a face full of burnt powder and gas if you are a 
left-handed shooter. Needless to say, repeated 
stoppages are in order. The action is quickly 
contaminated with powder residue due to its 
being blown out the wrong way! 

Firearms in .22 rimfire caliber have, for over 
1 00 years, suffered from the toy or plinker 
stigma. The average shooter will accept mediocre 



ammunition, cheap and unreliable accessories 
but, above all, the poor guy will lay out more 
money than he did for the gun for a couple of 
high capacity magazines only to have few work 
properly! Does he complain to the manufacturer 
or request a replacement or refund? No, he 
simply clears the stoppage and accepts it as the 
nature of the beast. It doesn't have to be that 
way! This same shooter w ould in no way accept 
this performance in his hunting rifle nor would 
a law enforcement officer accept this perform- 
ance from his service arm. 

There is a 50 round magazine available that, 
with some modifications and testing, can be 
made 98 to 99% reliable and that's pretty good 
odds. A self -addressed stamped envelope to the 
author will bring you up to date on the care and 
feeding of aftermarket magazines. 

Wayne Thornbrugh 
14615 Hwy. 12 
Orofino, ID 83544 



2 



Which Configuration Is Best, The Front 
Mounted Bolt Arrestor Or The Rear? 



We believe there is a place for both and that 
you must make the choice based upon your 
needs and your capabilities. The rear mounted 
arrestor is easier for those with limited tools. 
We developed the rear mounted system with the 
do-it-yourself builder in mind because there is a 
milling operation involved on the bolt in the 
front mounted system. Although the operation 
is simple, you still must have a milling machine 
or access to one. 

We have fired over 10 thousand rounds 
through our rear mounted arrestor prototype 
with no stoppages (magazine failures excluded). 
You should be aware, however, that the arrestor 
is actuated, both lifted and lowered, by spring 
pressure. Conceivably, if the mechanism became 
contaminated enough with grease, wax. dirt 
and powder residue, the spring action which 
lowers the arrestor might not be great enough to 
overcome the added friction. 

In our testing this did not happen. However, 
we disassembled the gun for cleaning and 
inspecting every few hundred rounds. Antici- 
pating that the lowering of the arrestor could 
possibly be a problem with an extremely dirty 
gun, we ran a test of 100 rounds fired with a 
locked arrestor, allowing the full blow back 
force of the bolt to be taken by the arrestor lug. 



Nothing came apart, no damage was done 
except a very slight marking of the bolt and a 
very small upsetting of the arrestor lug surface. 

In the front mounted bolt arrestor system the 
arrestor is cammed down by the positive action 
of the hammer mounted cam-down pin. The 
arrestor is free to fail on its own weight since all 
spring pressure is removed before the hammer 
reaches the firing pin, but there is not enough 
time for this to happen since its speed of fall is 
slower than the movement of the bolt. Hence, 
the cam-down pin on the hammer for fast, 
positive action. 

If you have read this far and you think you 
want to tackle the job, consider this: it cannot 
be done and made to work with any degree of 
reliability if you do not have access to a good 
drill press. You must, also, have access to an 
oven or torch for annealing and heat treating. 
This can be done with a throwaway propane 
torch if you have a good tip assortment. You 
will need a quality dial indicating caliper to lay 
out the hole locations in the trigger housing and 
various parts. If you have a heavy duty drill 
press, it can be equipped with an X & Y feeding 
milling table and used for any required milling 
operation. 



3 



SELECT FIRE 10/22 



GENERAL NOTES: 
Please read before beginning conversion. 



1. Please wear adequate eye protection during all 
operations, both machining and shooting. 

2. There are 4 different variations which can be 
used depending on your personal choice: The bolt 
arrestor can be either front mounting type or a rear 
mounting type. The modification to the trigger can 
be done 2 ways. The simplest way requires your 
trigger finger to exert some upward force at the time 
the trigger is pulled. This causes full auto firing. A 
normal, straight back pull fires semi-auto. A more 
sophisticated modification features a select lever 
that allows you a positive selection between full and 
semi-auto. 

3. You may substitute 3-48 socket head screws for 
the 3-56. Obtain them all .250 long. You will need 
one that length— the rest can be cut shorter. 

4. Unless you are experienced at heat treating and 
have a furnace you are probably better off to make 
the necessary parts from flat ground mild steel and 
case harden. 

5. You will need an extra .125 dia x .960 long dowel 
pin for the auto-sear. Use the Ruger ejector pin for 
the auto-sear and use the new pin for the ejector. 

6. There is a small lip on most of Ruger's trigger 
housings where the trigger comes thru into the 
trigger guard. Remove enough of this to allow free 
movement of the select lever if you are building the 
Model II mechanism. 

7. There is no alteration to the ejector when using 
the front mounted arrestor. The long arm of the 
auto-sear spring is set behind the ejector pin. A 
small rod with a notch filed in the end makes this 
easy. The hammer mounted arrestor lifting spring 
arm goes to the right of the long arm of the auto-sear 
spring. In other words, from left to right; arrestor— 
ejector— long arm of auto-sear spring— arrestor 
lifting spring arm. 

8. The sear surface of the auto-sear must be fitted 
to the auto-sear notch of the hammer with enough 
height to allow the trigger sear to move under the 
original trigger sear cut in the hammer. There 



should not be excessive clearance, otherwise the 
hammer will fall too violently down onto the trigger 
sear and over a period of time could cause damage 
to the sear surfaces. Just enough clearance to allow 
the trigger sear to move easily under the hammer 
notch with no binding is what we re after. One good 
way to determine this clearance is when the auto- 
sear is pushed off by hand the top of the hammer will 
move about 1/8" forward when dropping to trigger 
sear engagement. 

9. When using the front mounted arrestor, a .187 
dia x .950 long slave pin must be used when 
assembling the trigger housing to the receiver. 
Assemble the trigger housing and all parts in place 
using the slave pin to position the arrestor. Retract 
the bolt 1/4 inch or so and place an empty .22 rimfire 
case or equal space between the bolt face and 
barrel. Place trigger housing in receiver and insert 
rear receiver cross pin first. Insert front cross pin, 
pushing out and replacing the slave pin. Do this with 
action upside down and insert cross pins from near 
and push thru, going away from you. This will 
prevent binding. Caution: these are push fits, not 
drive fits! 

10. Where screws must be locked after fitting final 
assembly, they can be either Loc-Tite or a binding, 
female thread can be cut as follows: Using a starting 
tap (longer taper) only partially tap, leaving a couple 
of threads undersize so as to bind on the screw 
threads. You might wish to practice this on a scrap 
of metal before tapping the actual part. 

11. When you are ready to test fire, first do it on the 
workbench. WEAR EYE PROTECTION! Remove 
bullet and powder from a few rounds and insert one 
in the chamber. With the barrel in a padded vise and 
the action upside down, it is easy to fully retract the 
bolt, select semi orfull auto with the other hand and 
let the bolt slam closed. Run several rounds thru and 
inspect the firing pin indentations. The indentations 
should show no discernible difference between 
semi and full auto. 

12. Unless otherwise noted, all dimensions are in 
inches. 



4 



Fitting The Auto-Sear Trip Tolerance 



Disassemble the hammer strut and spring. 
Wind a spring from .029 spring wire to 
temporarily replace the regular hammer spring 
and reassemble. If you use the regular hammer 
spring while adjusting the auto-sear it will 
damage the sear surface since it has not been 
hardened yet. 

Assemble the bolt, cocking handle and recoil 
spring into the receiver. Secure the barrel in a 
padded vise, action upside down. Assemble the 
hammer assembly and auto-sear with spring 
into the trigger housing. The long arm of the 




A full auto sear is shown here. Note that the tang has 
a slight bend. A slight bend Is necessary during final 
fitting. This adjusts the auto-sear to trip at just the 
right time. 



auto-sear spring is set behind the ejector pin. 
Retract the bolt slightly and place an empty .22 
case or something similar between the bolt face 
and the face of the barrel in order to insure that 
the position of the auto-sear trip pin is behind 
the auto-sear tail. 

Place the trigger housing in the receiver and 
secure with the 2 receiver cross pins. Insert the 
bolt stop pin into the receiver. Remove the 
empty .22 case holding the bolt partly open and 
place a .020 feeler gauge between the bolt face 
and the barrel face opposite the extractor side 
of the bolt but not deep enough to allow the 
firing pin to strike the feeler gauge, otherwise 
the firing pin will be damaged. 

Holding the feeler gauge in place retract the 
bolt to full recoil and ease it back towards 
battery— easy does it, don't let it slam back into 
battery. Ease it back all the way, maintaining 
control with the cocking handle. You should be 
able to feel when the trip pin on the bolt first 
makes contact with the auto-sear tail. 

Ease it on closed against the .020 feeler gauge. 
If it trips you will hear the hammer fall. If it does 
not trip, remove the feeler gauge and try again. 
If it trips you are somewhere between .001 and 
.020 from full battery position when the auto- 



5 



SELECT FIRE 10/22 




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SELECT FIRE 10/22 




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SELECT FIRE 10/22 



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.925 




Hand wind around 1/8 rod secured 
in bench vise. 



AUTO-SEAR SPRING 

Hand wound from .029 stock 



9 



SELECT FIRE 10/22 



T 

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.390* 



.112 



.093 R 



.093 



1.030 



.135 



.150 

r 

.352 



12SDIA PiVOT 
PIN HOLE 

.093 



.218 



.190 



.500 



.210 



200 



Scale: 2:1 



AUTO-SEAR 



* The height of the sear surface is machined 
slightly high in order that it may be fitted to the 
mating sear notch on the hammer during final 
tuning. 

T.E.K. auto-sears are made out of 0-1 oil 
hardening flat ground steel flats (3/16 x 1/2 
stock). If you wish to use the same it can 



probably be found at a local tool & die shop in 
small pieces. Otherwise, it normally comes in 
18-inch lengths, 

To heat treat, bring the piece to about 1,550 
degrees F and quench in oil. Draw for at least 1 
hour at 400 degrees F. You can use the kitchen 
oven for this. NOTE: Do not heat treat until all 
final tuning and adjusting is done. 



10 



SELECT FIRE 10/22 




This photo of modified trigger housing reveals 3 
things: The forward mounting pivot pin (A); The bolt 
release lever (B) which replaces the original bolt 
hold-open lever; The Mod II select lever (C) which Is 
In the full auto firing position. 




Trigger mechanism showing a Mod II select lever 
Installed. 

sear trips . Try to determine the clearance even if 
it's very wide. In all probability you will have to 
bend the auto-sear tail forward. Don't be afraid 
to overbend because it's much easier to bend it 
rearward since it's up against the hammer, but 
to bend it forward it must be removed from the 
trigger housing. If after bending, you find that 




This photo shows the select lever moved into the 
semi-auto firing position. 




Modifications to the original bolt are shown here. An 
auto-sear trip pin is added. The mill cut shown is 
used with a forward mounted arrestor. 

you have no clearance, bend the tail rearward a 
little at a time until it falls within tolerance. A 
small (4 inch) Crescent wrench is ideal to bend 
the sear tail with. The auto-sear should trip 
between .010 and .015. After breaking all sharp 
edges (careful with the sear surface), the auto- 
sear is ready to heat treat. 



11 



SELECT FIRE 10/22 



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12 



SELECT FIRE 10/22 




13 



SELECT FIRE 10/22 




7/32 dia thru and enlongate as shown. 
c l There can be no binding between screw 

head and trigger. 



Scale: 1:1 

TRIGGER SEAR— SELECT FIRE I 



14 



SELECT FIRE 10/22 




.187 radius. 

(using 3/8 end mill, machine flush with surface "A" 




.093 dia— thru 
(Drawing may be used 
as a template except 
for hole location) 



.093 dia— thru 

(CAUTION— lay out hole location on both 
sides and drill, using a smaller drill, from both 
sides, then finish drill to .093 dia.) 



.170 



170 



SELECT FIRE II LEVER 



.475 



H-.125 



.093 drill rod. 

Silver solder to lever. 



J i 



.047* 



.062 



* The .047 (max) deep flat on shaft 
is cut by hand with select lever in 
place assembled to trigger and held 
in semi-auto position. Do not cut 
beyond 1/2 the diameter of the shaft. 
Final fitting can be accomplished by 
reducing the height of the "A" surface 
of the trigger sear. In final fitting, the 
lever should move forward with no 
binding and cam trigger sear down 
against sear spring pressure. 



TRIGGER SEAR MODIFICATION 



Scale: 1:1 




120 



h-.075 



End view 



TRIGGER, TRIGGER SEAR & SELECT FIRE II LEVER 



15 



Full Auto Operation— Rear Mounted Arrestor 



With a loaded magazine inserted, a round 
chambered, Select Fire II lever "1" forward and 
safety off, you are ready to fire full auto. The 
trigger is pulled (slight upward pressure is 
required on Select Fire I), the hammer drops 
and the gun fires. 

The bolt starts the recoil cycle camming the 
hammer rearward which, with the bolt arrestor 
spring i4 4" attached, begins to exert lifting 
pressure against the arrestor actuating pin "6" 
attached to the bolt arrestor "7'\ This spring 
lifting pressure is increased progressively as the 
hammer is cammed rearward. However, the 
bolt arrestor "7" is limited in its upward 
movement due to its contact with the bottom of 
the bolt. Just short of full recoil the auto-sear 
"3" is rotated rearward under spring pressure 
and is in position to catch the hammer on its 
auto-sear notch as the hammer starts to follow 
the bolt back in counter-recoil 

In counter-recoil the bolt strips another round 
from the magazine and chambers it. When the 
bolt is within .0 1 5 to .0 1 8 of battery position the 
bolt arrestor "T will rise behind it. The bolt will 
make contact with the breech face of the barrel 
and start to bounce rearward, much like a 



hammer striking an anvil. However, its bounce 
is limited to the .015 to .018 clearance between 
the lug on the arrestor and the back of the bolt 
which is measured when the bolt is fully closed. 

While this was taking place another sequence 
was happening. When the bolt was .010 to .015 
from battery position, the auto-sear trip pin "5" 
mounted to the bolt tripped the auto-sear off its 
sear notch on the hammer. Although these two 
sequences take place almost simultaneously, 
the bolt is allowed enough time to strike the 
breech face, bounce back against the arrestor 
lug and return to battery as the hammer is 
falling. Thus the hammer is allowed full access 
to the firing pin. 

The hammer, in its fall, will describe an arc of 
about 60 degrees. When the hammer reaches 
about the last 20 degrees of this arc, the bolt 
arrestor actuator spring "4" will start to exert 
downward pressure on the arrestor pin "6" 
This spring pressure increases during the last 
few degrees of the hammer's movement, thereby 
lowering the arrestor away from the bolt in 
order to allow the bolt, in counter-recoiK to 
move back over it. (In the front mounted 
arrestor configuration, the bolt arrestor is 



17 



SELECT FIRE 10/22 




18 



SELECT FIRE 10/22 




19 



SELECT FIRE 10/22 




20 



SELECT FIRE 10/22 



cammed down by the arrestor cam-down pin 
"12".) The gun fires again and another cycle 
starts. 

In semi-auto all of the foregoing takes place 
except when the auto-sear is tripped, the hammer 
falls only down to the trigger sear which catches 



it and awaits the trigger being released and 
again squeezed. All full automatic operations 
within the gun take place before semi-auto . 

You can readily see that Ruger's original 
design has not been changed, only added to. All 
of the reliability is left in the gun. 



21 



SELECT FIRE 10/22 




22 



Fitting Rear Arrestor To Bolt Clearance 



Assemble the bolt in the receiver without the 
cocking handle and recoil spring. Place the 
arrestor on its pivot pin in the trigger housing 
and place the trigger housing in the action using 
the 2 receiver cross pins. 

Push the bolt forward to the battery position. 
If the arrestor lug falls behind the bolt, measure 
the clearance between the bolt face and the 
barrel face. If the arrestor does not fall behind 
the bolt, check to see that it lies flat against the 
side of the trigger housing. Using a small rod or 
screwdriver, attempt to push it into position 
behind the bolt — gently! If it doesn't go behind 
the bolt, disassemble and take a ,0 10 to .0 1 5 cut 
off the arrestor lug and try again. Once the 




This drawing may be used as a rough template to 
make the hammer bushing clearance cut. Be careful 
not to over-cut The arrestor must stay in place 
behind the hammer bushing as It moves up and 
down. It must be cut deep enough to allow the top of 
the arrestor lug to retract enough to be level with the 
top of the trigger housing. 

arrestor lug locks the bolt, you will know where 
you are since you can measure the bolt face 
clearance with feeler gauges. Attempt to get a 
nominal clearance of .020. 



23 



SELECT FIRE 10/22 




NOT TO 




.020 brass 
hammer 
bushing 
spacer 



Bolt arrestor 
actuator spring 



except for spring contour 
and cam-down pin 



REAR MOUNTED ARRESTOR 
PARTS VIEW 



24 



SELECT FIRE 10/22 



8-40 thread 



Scale: 4:1 



i 



.160 



1 



,215 



,094 



REAR ARRESTOR PIVOT PIN 

(Needed only if you are using the rear mounting arrestor) 



The rear arrestor pivot pin is best made from 
#20 drill rod. However, it can be made from an 
6-40 screw. There must be an unthreaded 
portion (.093) after the head is removed. This 
portion protrudes through the trigger housing 
for the arrestor to pivot on. These 8-40 gun 
screws will vary In hardness so the first step is 
to anneal. The diameter of these screws will 
vary from .161 to .162 dia. Since the pivot pin 
hole drilled in the arrestor will be .161 dia, you 
may have to machine a small amount off the 
screw to allow for a perfect fit. The arrestor 



should pivot freely and yet have no slop. Fit the 
pin to the arrestor, not the other way around. A 
slot cut In the threaded end will assist tightening 
It In the trigger housing. 

When complete, the screw can be rehardened 
and drawn to a dark blue color, 900 degrees F if 
you have an oven. 

In the final assembly the pivot pin must be 
epoxied in the threaded hole of the housing. 
We suggest using either an aluminum or steel 
epoxy. 



25 



SELECT FIRE 10/22 



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27 



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ADJUSTING THE REAR MOUNTED ARRESTOR ACTUATOR SPRING 



Adjust the spring to approximately 40 degrees 
from hammer surface, as shown. Assemble the 
hammer to the trigger housing without hammer 
spring and strut. With the hammer in the 
upright position place arrestor on pin. Move 
hammer back to cocked position and lower 
arrestor to spring. Slip spring loop over arrestor 
actuator pin and lower hammer and arrestor 



until ejector pin can be inserted over top of 
arrestor arm. The ejector pin limits upward 
travel of the arrestor. The spring angle in 
relation to the hammer should be adjusted so 
that It will start to apply downward spring 
pressure when the hammer is 20 degrees from 
vertical. 



28 



SELECT FIRE 10/22 







— 13/16 — 




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.080 OFFSET 



EJECTOR PIN HOLE 




; Grind this radius back 1/16 to allow full retraction of 

.030 magazine latch plunger, since overall length has 

been shortened due to bending. 



NOT TO SCALE 



ALTERATION OF EJECTOR 

(Rear Mounted Arrestor Only) 

Ejector must be annealed before bending. After 
completion, reharden and draw to 500 degrees F for 
1 hour. 



29 



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SELECT FIRE 10/22 




Fitting Front Mounted Arrestor To Bolt Clearance 



The same basic procedure is followed as with 
the rear arrestor except a 3/ 16 diameter slave 
pin, .950 long, is used to assemble the arrestor 
and then replaced by pushing through the 
regular front receiver cross pin after the rear 
receiver cross pin has been installed. If the 




If the magazine latch plunger does not fully 
retract grind thla surface back to clear 
original bolt lock clearance cut In magazine 



1/8 drill thru 



ARRESTOR RELEASE LEVER (Optional) 
Make From 5/64 x 1/2 Flat Ground Stock. 

This drawing may be used for template. Distance 
"A" is critical and must be carefully fitted to arrestor 
cut. The proper fit is a slight looseness when the 
arrestor Is in the up position. There must be no 
binding. After fitting, polish both the arrestor cut 
and the lever end. The lever fits into the original bolt 
lock slot and the visible end is shaped to match the 
bolt hold open lever that must be discarded. It may 
be necessary to clean the slot slightly with a flat 
needle file. After final fitting, harden. 



^1 



Use this drawing as a rough template to shape cam 
surface. Final fitting of cam surface should be done 
by hand, so leave some extra metal. 




Shown here is a small pin that has been added to the 
hammer. This pin trips the bolt arrestor as the 
hammer travels forward to strike the firing pin. 

arrestor lug falls and locks the bolt when it is 
pushed into battery, measure the clearance 
between the bolt face and barrel face. The final 
clearance should be between .015 and .018. If 
the clearance is short, disassemble and place the 
bolt back into the milling machine and re-cut to 
bring the clearance to tolerance. 



33 



SELECT FIRE 10/22 




for magazine lever notch 

latch plunger (optional) 



BOLT ARRESTOR 



.062 HAMMER 
BUSHING SPACER 





STANDARD RIGHT 
HAMMER BUSHING 



NOT TO SCALE 




Arrestor 
cam -down 
pin 



ALTERED LEFT 
HAMMER BUSHING 



Arrestor 

lifting 

spring 

FRONT MOUNTED ARRESTOR 
PARTS VIEW 



34 



SELECT FIRE 10/22 




Scale: 2:1 



FRONT MOUNTED ARRESTOR 

Make from 3/32 x 1/2 inch flat ground stock. 



To fit cam surface "A" to arrestor cam-down 
pin attached to hammer, proceed as follows: 
Assemble Into trigger housing using the front 
receiver cross pin. Insert the ejector pin through 
the trigger housing and arrestor. The ejector 
pin limits the arrestor movement. In the up 
position the arrestor lug should protrude .090 
to .100 above the trigger housing. 

Holding the arrestor in the up position, move 
the hammer forward. The cam-down pin should 
make first contact with arrestor cam surface 
when the hammer is 17 to 20 degrees from 
vertical. The cam surface curve from first 
contact with the pin to the fully cammed down 
position (hammer vertical) should describe a 
slight parabolic curve. The arrestor lug should 
be level with the top of the trigger housing 
when the hammer is vertical. Caution: At this 
time make sure that the bottom of the arrestor 
is not bottomed out against the hammer 
bushing or the ejector pin. There must be 
enough clearance to allow the hammer to 
move about 2 degrees past vertical. This will 
assure clearance between the cam-down pin 



and cam surface movement downward. Other- 
wise, the pin will bend or break. With the bolt 
assembled in the gun, the hammer is limited in 
its forward movement to the vertical position 
by the back of the bolt. The ejector pin 
clearance hole in the arrestor may be enlarged 
slightly if more up or down movement is 
required to meet specifications. 

Polish arrestor cam surface before heat 
treating. If you are using 0-1 oil hardening 
steel, draw arrestor for 2 hours at 900 to 925 
degrees F after hardening. If you do not have 
equipment for this heat treating then make 
your arrestor from mild steel (flat ground 
stock) and case harden. Kasenit works well. 
Follow the directions on the can and give it 2 
treatments. The arrestor takes a lot of stress at 
1200 rounds per minutel The auto-sear can, 
also, be made from mild steel and case 
hardened. Mild steel flat ground stock can be 
had in both 3/16 x 1/2 and 3/32 x 1/2. It cannot 
be had in 5/64 thickness which is needed to 
fabricate the arrestor release lever. 



35 



SELECT FIRE 10/22 




36 



SELECT FIRE 10/22 



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37 



SELECT FIRE 10/22 




38 



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39 



SELECT FIRE 10/22 




Altered parts for front mounted arrestor. As stated in text, there are 
advantages to both front and rear mounted arrestors, with the final 
choice being determined mainly by the machining facilities and expertise 
available to the person doing the conversion. 




prototype differs slightly from the drawing and has 
extra lightening holes added. 



40 



ADDENDUM 



(The following was an instruction sheet supplied 
by the TEK plant when they were producing these 
converted Ruger 10/22's.) 

The bolt lock and spring have been removed 
from your gun to make room for the conversion 
parts, otherwise the gun utilizes all the remaining 
parts and operates just as it came from the Ruger 
factory in the semiauto mode. In the full-auto 
mode it still operates as it came from the Ruger 
factory except the sear is operated automatically 
by the cycling bolt as long as the trigger is held 
back, Twenty-two ammo is greasy, waxy and has 
a tendency to leave a lot of fouling behind in the 
action. It is not, however, necessary to completely 
disassemble the gun for normal cleaning. It is 
prudent to clean the action after about 500 rounds 
by retracting the bolt and placing a wooden dowel 
of about 3/16-inch diameter by l :, /«-inch long 
between the bolt face and the breech end of the 
barrel to hold the bolt open since the bolt lock is no 
longer in the gun. 

With an old toothbrush or something similar 
dipped in Hoppes, WD-40, etc., scrub the bolt face 
and parts of the action that you can reach. Pay 
particular attention to the recessed bolt face and 
extractor slot in the barrel. Dry with a lint free rag 
or cleaning patch. Q-tip sticks are handy for 
cleaning. Spray very lightly or wipe down with 
Break Free, WD-40, etc. Clean the barrel in the 
normal fashion but, leave a dry chamber as you 
should with any rifle. With such cleaning, your 
gun should function properly for thousands of 
rounds. 

If and when you must break the gun down 
completely, follow the procedure described here to 
prevent possible damage to the parts. The bolt 
arrestor lifting spring which is attached to the 
hammer MUST lay on the right side of the long 
arm of the auto-sear spring. Looking down on the 
trigger housing, the parts and spring should be as 
follows, from left to right: Bolt arrestor, ejector, 
long arm of auto-sear spring set behind the ejector 



pin, bolt arrestor lifting spring. When all parts 
have been cleaned and reassembled in the trigger 
housing, using the 3/16-inch diameter slave pin 
supplied, lay the barrel and action on the bench, 
barrel pointing to your left, action upside down. 
Using the bolt handle, retract the bolt about 
1/2-inch and place an empty .22 case between the 
bolt and barrel face to hold the bolt partially open. 
Place trigger housing into the receiver and insert 
the rear receiver cross pin. Insert the front cross 
pin, pushing out and replacing the slave pin. Both 
cross pins are push fits— DO NOT FORCE. 
CAUTION— the front cross pin must be inserted 
going away from you, or, in other words, from the 
bolt handle side (closest to you), through to the 
serial number side. The reverse of this procedure 
can damage the bolt arrestor which is fitted to 
close tolerances. 

Wear shooting glasses and keep other people 
clear of the right side of the gun when shooting. 
Empty, hot cases really flow from the 10/22 in 
full-auto. Extractors have, also, been known to 
blow off 10/22's. Have fun but be careful, the 
firepower of this gun is awesome. 

You can remove all TEK parts, replace the bolt 
lock and spring, and your gun works just like the 
original. 

The original bolt lock has been replaced with a 
look-alike lever that retracts the bolt arrestor. Pull 
back on the lever to retract the arrestor to open the 
bolt when the hammer is cocked. This allows you 
to unload the gun if there is a round in the 
chamber. 

To adjust the rate of fire, use the Allen wrench 
supplied and tighten until the bolt will just stay 
open when retracted by the bolt handle. This is the 
ideal slow fire setting, although you can adjust it 
slower. To insure better reliability, test fire under 
extreme weather (hot and cold) conditions. 

CAUTION: The bolt cannot be opened if the 
hammer is down and the safety is on. You must 
place the safety on fire position to open the bolt 
when the hammer is in the fired position. 



41