CETME tutorial [Archive] - Militaryfirearm

tomoshenko

03-07-2007, 04:41 AM

Here is a short summary that Perro posted at one time:

if you want a g3, or hk91, buy a g3 kit, receiver, and start there
youll be FAAARRRRRRRRR ahead at that point.
The G3 has NEW parts readily available for it
the G3 has US MADE compliance parts readily available for it

by making your cetme into a g3, you are causing yourself soooooo many problems youre not even aware of yet

building it is easy on paper

install trunnion into receiver until it bottoms out on the rails - ensure trunnion is installed square, plumb, and true to the rails of the gun (look through the back of the receiver with a flash light and look for a trunnion installed not square with the rails)

weld trunnion into receiver once its straight

cocking tube is next, but this presents its own set of problems. If the cocking tube is not installed correctly, youll either have VERY hard problems cocking the gun, or your gun will destroy itself. There must be a very small gap between the end of the carrier tube, and the inside of the cocking sleeve. this gap decreases with wear the same amount that your bolt gap decreases with wear. Therefore, if you set your bolt gap to .010 you need .010 gap in the sleeve. If you set your gap to .020 then you need your sleeve gap to be set at .020
lets say you are aiming for .015 bolt gap which is a good number, then you want .015 gap in the sleeve too.
cut a small disk out of a .015 feeler guage. Cut it so it fits on the end of the carrier tube with tape or light epoxy, elmers glue, etc. It must be under the diameter of the carrier tube just barely.

with appropriate sized shim installed to carrier tube, insert complete bolt set WITH SHIM ATTACHED into the receiver and let it lock into the trunnion. the carrier tube will protrude out of the front of the receiver where the cocking tube normally goes.

insert the cocking tube with complete cocking mechanism installed (sleeve, cocking handle, pin, and spring) into the receiver and over the top of the carrier tube until it bottoms out on the end of your shim. make CERTAIN that your shim isnt bound up inside of the cocking sleeve and that the shim is squarely pushing the cocking sleeve against the sheet metal stop built into the inside of the cocking tube. Align the cocking tube to your likings (make sure the cocking slot is where you want it), clamp the tube to the receiver with a LONG wood style clamp and tack it in 1 spot - light heat, just enough to hold it. unclamp it and insert a copper rod inside of the cocking handle to back up the thin cocking handle - this prevents weld burn through and acts as a heat sink. weld the cocking tube to the receiver now.
one thing to know before welding the cocking tube. if when fitting the cocking tube to the carrier with shim you notice that it does not butt up squarely with the receiver, you need to measure how much gap is present in between the cocking tube, and receiver - this is a precision measurement. you should remove the same amount of material from the end of the carrier tube with a precision machine tool like a lathe, mill, or surface grinder. If your tube buts up squarely to the receiver with the shim installed to the end of the carrier tube, you should turn off a small amount of the shoulder on the cocking tube until it doesnt butt up to the reciever - go small amounts here until it clearly doesnt butt up - a .010 gap welds up nicely.

ONCE THE COCKING TUBE IS GAPPED AND INSTALLED CORRECTLY, REMOVE THE SHIM OFF THE END OF THE BOLT CARRIER. THAT SHIM IS ONLY TO GAP THE COCKING TUBE AND YOU DONT WANT TO SHOOT WITH THAT SHIM ON IT CAUSE IT WILL DESTROY YOUR GUN

so, now you have the trunnion installed and the cocking tube installed, now to the barrel

insert the bare barrel into the end of the receiver and through the trunnion until it bottoms out on the trunnion - press the barrel in from the rear of the receiver. press it in until its close to where it needs to be, remove the gun from the press, install the carrier and check bolt gap - if gap is too much press the barrel in a little more until gap is right. if gap is not enough, press it back out and start over. one thing you need to take account for is that the gap shrinks a bit after you first shoot it - how much?? thats a guess. if you press your barrel until it gaps at 20 thou, it may end up at .017 after you shoot it - may end up at .015 after you shoot it?? who knows?, but take that into account, you can always get undersize rollers to accomodate too much gap.
once your barrel is gapped right, drill it through the barrel pin hole with a 5mm drill bit and drive in the barrel pin. you will probably need to locate the barrel pin hole in the receiver if its a century receiver, cause century doesnt drill the barrel pin holes.

now, you have the cocking tube, trunnion, barrel, and barrel retaining pin installed to the reciever

now to the triple front frame
flux the inside of the triple frame, and the barrel where the triple frame will rest. install the triple frame to your barrel and index it to your rear sight - once perfectly indexed, clamp it all so it cant move. heat it up with the torch (barrel area and triple frame) and silver solder the triple frame to the barrel from behind the triple frame. once cool, and set, and you are happy with the alignment, hold off before drilling and pinning it with the sling eyelet pin - more on this at the end of this post.

convert your trigger pack to semi auto only, and your grip frame
install the shelf to your trigger box by welding it, and install the shelf inside of the grip frame. install your us made semi auto trigger parts, and install this set of parts to your gun - assemble everything else too (buttstock, handguard, etc)

go shooting, but take a torch with you
if it shoots to point of aim, you are good to go
if it shoots badly to one direction heat the triple frame/barrel up to melt the solder and move it a little bit and let it cool back down
shoot again - once centered stop shooting for the day.

drill your barrel for the sling eyelet pin
insert a new sling eyelet pin from RobertRTG and peen over

refinish

done

it SOUNDS easy, but there is ALOT to it

it isnt an AK, but it is similar in build to one
there is a HUGE difference though
AKs you dont have to worry about bolt gap so you just install the already headspaced barrel and trunnion to the receiver - cetmes and hks you really do need to worry about bolt gap cause most kits wont gap anywhere desireable cause they are well used.
and you dont have a cocking tube on an AK that needs to be gapped correctly.

As i told you before, if this seems too much for you, you should get on big50s waiting list. I have watched him assemble HKs, and CETMEs before, and he knows his stuff, and he will build you something youll be REALLY proud of when its done.

i cant tell you how many times people have asked me to build there guns for them over the last couple of years. Most people dont understand that i do not have the proper FFL to accept a firearm from people so im posting this in hopes that other people who may read this will understand that i cannot do this kind of work for you - contact big50 at big50hk.com, he knows what he is doing with these guns, and will build you something you are proud of.

hope this helps

if you searched the forum and read through enough of the posts, you would find everything i just typed many times over, and much more.

good luck on your build

Mike
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