Fire Control group semi auto mod.

[Arizona Ranger]

Hi guys,
Does any one have the information on the modification of the FA fire control group (trigger pack) to semi auto. Another I wish I had saved that before the old site went down.
Thanks,
Mike

[landtoy80]

Are you wanting to use compliance parts or cut the full auto part to semi?
I took a FA FCG and made it semi but most of the the info was off Perro's site.

I had FA and semi FCG and just copied the semi. I used a Dremal to cut the parts.

[Arizona Ranger]

I was planning on cutting the Full auto to semi. I am going to have to use compliance parts elsewhere.

Do you know if US parts means made my a licensed manufacturer or can I have a gun smith make a few parts for me? My dad is a cabinet maker, he said he could make me a butt stock and fore end with no problem in what ever kind of wood I want. I can get a US made pistol grip from a bunch of places and a us receiver and us flash hider/break. That brings my count to 5 I could use a G3 charging handle and have a smith make a hammer or sear.

Does this sound legal, okay?:wall:

[Enigma Nostra]

Should be fine. Only thing I warn your dad about is that making cetme stocks are a PITA from what I hear.

You should document the production of the parts well, and mark them somehow as US parts, just to cover your ass. If you can find them, I think you would do better buying the FCG parts than making them.

-E

[rustypirate]

If the parts are made from US material and US sources, and not just altered imported parts, then yes, it is legal.

It would probably be cheaper to replace the entire trigger/grip frame assembly with the G3 version then to get those parts custom made.

You can replace the hammer, sear, trigger, trigger box, pistol grip in just that assembly. Add to that the charging handle and receiver, and you are done.

[landtoy80]

I see nothing wrong with cutting down a FA FCG and using a US stocks or Thermo mag. Who knows ,you may be able to find some US parts later.

I posted some pic's on the CETMEFORUM but they got :flamed:

[rustypirate]

I don't see anything wrong with that either, but he was talking about having FCG parts manufactured, which would be very pricy.

[landtoy80]

I guess you could Dremal your own parts, that is if you started with the right grade of steel. Would you have to heat treat them?

[cimmaronkid]

Depends on the parts, but the general answer is "yes". Any sear areas would have to be heat treated. That pretty much takes in the trigger/sear/hammer groups. There are several products on the market to case harden parts and that should work depending on the depth they are hardened to.

[Arizona Ranger]

Thanks for the input. I'm still in need of information on what FA parts to get rid of and what to cut and where for semi auto use.

[jfowl31]

Not my drawings, but from a reputable source on gunboards.

http://www.gunboards.com/forums/uploaded/gw11/200737191234_MVC-015F.JPG

http://www.gunboards.com/forums/uploaded/gw11/20073719133_MVC-003F.JPG

[M1 Tanker]

I got these a long time again of PCS, Inc's website.

468

469

470

471

472

473

474

[drhall762]

This board is fantastic. Great info on the process and once again a picture is worth a thousand words.

:thanks:

Dave :sniper:

[Arizona Ranger]

Thanks jfowl and Tanker that's what I was looking for.
Thanks for everyone else's input too.
Mike:thumbup:

[vista461]

How critical is the .400 dimension? if it's .410 or .420 is that all right? And at .045 thick for the plate, it's basically just a piece of thicker sheet metal right?

[rustypirate]

The .400" measurement is not critical, so long as the sear pin hole is destroyed.

I think that a lot of people have used the cut out scraps of the cage to weld into place.

[vista461]

Got my box cut today and am going to weld in the plate in the morning. I also cut the tang off the hammer pawl. So that just leaves the notch on the hammer to be ground off as far as trigger group mods , correct?

[Big Steve]

This is great info, needs to be a sticky.
Steve

[drine]

Courtesy of grifter95

[rideronthestorm]

Thank you all for the detailed information, photos, and drawings. This has inspired me to upload my PSL (Romanian Dragonov) drawings to appropriate forum.
LeDoyle

[rustypirate]

Thread stuck

[rbthntr64]

Doesn't the hammer get modded also?

[jettag]

Don't forget to give those contact points a nice hone & polish You'll be nicely surprised what a difference it makes in the takeup/break of the trigger.
Then...
Reinsert FCG into the grip frame, lube & work it by hand while you watch TV for an hour or two.

Shlip*SNAP Vs. Crankle......................ploop, Aw S#^%!

Mine lost a few Lbs. & has a clean, crisp break. She's sure a sweet shooter now!

[rbthntr64]

What mods are done to the hammer? I am making a Hk51 style pistol from my kit and need to know what has to be done to the trigger pack besides the shelf. Being that it is a pistol build 922r doesn't come into play.
:America::thumbup:

[Daffy]

On the hammer you have to grind the auto sear catch down flush.

Also: In the pics that M1 Thanker posted it shows the interupting catch being replaced or disscarded. You need to cut the tail off, the part that rides on the selector switch. You can see in the lower photo of Tanker's post, the interupting catch modified and mounted to top of the trigger sub assembly. This mod prevents it from staying out of engagment from the hammer for full auto.

You may also need or want to add a trigger rear travel stop. I'm in the process of modifing mine and found that the trigger way over travels to the rear. I understand this is a requirement on the HK design (which is different that the cetme)

Another thing, not a legal requirement from what I understand, but recomended to keep you more hasseled free is to make a selector switch stop so it doesn't swing into the original full auto position. Should an officer decide to inspect your rifle and he sees the selector go into full auto possition, he may just decide to take it back with him to the office for further inspection or add to his collection of collections. Looks like Century used a dull pointed punch from the inside of the grip frame to make a little weenie popping out on the sweep area with the fire, safe postition indentations.

[sdk1968]

good helpful thread. thanks

[Daffy]

Regarding trigger over travel and making a trig stop I mentioned above. I looked at it again. The selector acts as the trig stop. I was working it with out the selector in place. But it is required in the HK pack to my understanding.

[Grasshopper]

Arn't you supposed to drill a hole and stick through a 1/16th pin and weld it somewhere? I'm looking for my G3 stuff but can't find the instructions for it.:icon_neutral:

[Daffy]

Arn't you supposed to drill a hole and stick through a 1/16th pin and weld it somewhere? I'm looking for my G3 stuff but can't find the instructions for it.:icon_neutral:

Only for HK. On the cetme, the sping arrangment is differnt. Really, the cetme is a much easier assembly to modify. If you are building an hk rifle, and you can get US made cetme hts,(or if you already have US parts count, not needed) its easier to use the cetme assembly for the hk build. Of course, you're building an HK to have an HK and not a franken hkcet. But if you're not particular....
There's no trig travel stop to install, no new pin/sear spring relocation needed and no new or modified sear spring to hassel with. That spring alone is 15 bucks from PTR91, if they still sell them.

[Daffy]

Cetme mods for semi auto

[Grasshopper]

Thanks Daffy, I needed that. I was wigging, my gun stuff is in the vault at home.

[Daffy]

Actually, you can toss out that part I said to use as spacer on the 2nd photo if you wish. I used to use it, but don't anymore, The rear horizontal lug things on the trigger work well, as intended.

[bolex]

[QUOTE=rustypirate;2951]If the parts are made from US material and US sources, and not just altered imported parts, then yes, it is legal......QUOTE]

I am going to disagree on the "US material" statement. The raw material does not have to be made in the US. You can go down to HD and buy a sheet of steel and make your own trigger box. The steel sheet does not have to be identified as "made in USA". I think the main issue is that you can not take a foreign part modify it and state it is US part if it has the same function. You can take a piece of a foreign receiver and make a trigger from it and call it made in the US. You can not take a foreign trigger and modify it and call it US. I have seen a BATF letter on this subject but do not remember where. Making the part out of US material is a good thing just don't try to find titanium that is "made in USA".

[Lon Moer]

These are the HK directions, from the old FAC/CIA kits from back in 2000(?)

http://i403.photobucket.com/albums/pp112/Lon_Moer/HKsemi-automods.jpg
http://i403.photobucket.com/albums/pp112/Lon_Moer/HKtriggerboxmods.jpg

[robdog]

Wow, the CETME SA mod is alot easier than the HK SA mod. Now if I could only get my build flat to bend right. Anyone have a jig they loan or rent out?

[gtty]

Not my drawings, but from a reputable source on gunboards.

http://www.gunboards.com/forums/uploaded/gw11/200737191234_MVC-015F.JPG

http://www.gunboards.com/forums/uploaded/gw11/20073719133_MVC-003F.JPG

Anyone have these images. They are Red X's now.

[jfowl31]

All of the images I've posted from gunboards are I THINK in this thread.

The poster is a guy who goes by GW11... I've tried a few times to get him to post over here, but so far, no dice.

Here's his thread...

http://forums.gunboards.com/showthread.php?t=2029

[gtty]

Thanks!!:icon_biggrin:

[rbthntr64]

:America: This info is just what I was looking for! I have saved it as a PDF and will see if I can condense it and have it put as a sticky at the top of this board.

[patjsimpson]

Anything like this for the G3?

thanks,
Pat

[mitchstoner]

There is a ton of good info here, BUT as a CETME/HK build rookie, I've got to say that separating the info pertaining to HK from the CETME info has been pretty confusing.

Does anyone need a project? I would like to see either the posts clearly labeled as to "HK" or "CETME," or maybe even separated into 2 threads.

Also, the CETME mods can now be radically simplified by use of Matt Yeaman's (turbothis) U.S. made fcg parts, and this thread predates Matt's parts.

[mitchstoner]

Turbothis (Matt) has manufactured some semi-auto fcg parts for CETME that greatly simplify the job of converting the CETME fcg to legal semi-auto configuration. His 2 parts are: 1) a combo trigger/trigger bar, which replaces 2 of the original parts; and 2) a hammer without the full-auto step or notch on it. Here's his thread in WTS: http://www.militaryfirearm.com/Forum/showthread.php?t=10785

I am a newbie to CETME's, and this fcg mod appeared a little intimidating, based on some of the posts in this thread. Since some posts in this thread deal with HK fcg mods, which are quite different in some respects, I thought this CETME-only post might be helpful to other noobs.

After doing my first one (and confirming with Matt that I hadn't overlooked anything), here is what you need to know:

Step 1) Pull the trigger box out of the CETME lower (pistol grip assembly). First you rotate the selector lever to a straight up position, then pull it out. Then lift the trigger box out.

Step 2) Remove all of the fire control parts from the box. This is basically just a matter of pushing out the pins and wiggling the parts out.

Step 3) Modify the trigger box as per instructions found earlier in this thread. See M1 Tanker's Post #12 for a pic, and Lon Moer's Post #34 for diagrams with dimensions that will work. Moer's diagram is of an HK trigger box so it doesn't look quite the same. Keep in mind, with a CETME the object isn't to eliminate the pin hole for auto sear, because you will be using that pin and the spring. But the mod eliminates the space where the auto sear would fit.

Or, turbothis also has new U.S. trigger boxes that meet BATFE requirements for eliminating the space for the auto sear. Here's a link to Matt's thread in WTS: http://www.militaryfirearm.com/Forum/showthread.php?t=13605

Step 4) Modify the interrupter catch and assemble onto the new trigger/trigger bar. The interrupter catch has a riveted pin holding it into the original trigger bar (also sometimes called sear, but that is confusing as there is also a "safety sear" and an "auto sear" in the original assembly). Pay close attention to the orientation of the interrupter catch in the old trigger bar, and use the pictures in this thread to be sure you will re-install it the same direction.

Drive the rivet pin out with a punch, it shouldn't take much effort. Carefully file off any burrs from the end of the pin you drove through the holes so it will start into the new combo trigger/trigger bar. Don't file the pin so it slips all the way in; it will need to be a snug fit, just a bit of a taper on the end so it will start into the hole.

The interrupter catch needs the "tail" ground off as per instructions found earlier in this thread. See Daffy's Post #25 for a description, and his Post #30 for a pic. Then install it into the new trigger/trigger bar. Be sure you have it oriented the same as it was in the old trigger bar. Caution, the thin interrupter catch arms of the trigger bar can break off if you don't support this when you drive the rivet in. If you look at these arms where the hole for the interrupter catch is drilled, you will see one of them has been milled thinner than the other. My recommendation is to lay the trigger bar on the anvil of your vise with the thin arm on top, the interrupter catch in place, and tap the rivet in. If it seems like it is going to take heavy pounding, stop and do a bit more filing on the pin. After the pin is completely in, turn the assembly over, and with the interrupter catch arm well supported, tap the end of the rivet pin with a center punch to slightly swell the end, to make it tight in the hole. Make sure the interrupter catch swivels freely.

Step 5) Assemble the parts into the trigger box. Most of the old parts are unneeded. The only old parts you need are the auto sear spring (but not the auto sear), the hammer spring and spacers, the ejector and spring, and the trimmed interrupter catch. (and all their pins of course) The auto sear spring helps as a trigger return spring. The "loop" of this spring needs to go under the front end of the trigger bar.

You will pitch the safety sear, old trigger, old hammer, trigger bar, hammer pawl, and auto sear.

Some of the instructions in this thread deal with modifying the hammer pawl and using the hub (round end) of the safety sear as a spacer on the trigger pin. Neither of these parts are necessary with turbothis' new parts. The arms of the hammer spring keep the trigger centered.

A few more tips:
Surplus parts often are thickly coated with cosmoline. I work best when my hands aren't all slimy. A toothbrush and mineral spirits, gas, or other solvent will get the parts clean after you disassemble them. From then on you aren't getting grease on your face if you scratch your nose.
Instructions somewhere deal with the easiest order to reassemble the parts, but I couldn't find them. Honestly, I had these parts in and out so many times I'm not sure what order worked best. Try trigger assy first, hammer/spring/spacers second, auto sear spring third, ejector/spring last. Then you can slip the selector in to see how it all works.
Try not to "dry fire" too much without catching the hammer, it will bend the front of the trigger box.
When you get one part assembled, it is frustrating to have that part's pin come sliding out while you are trying to get the next part in place. Use bits of masking tape over the ends of the pins after each is in place.


This post only covers the fcg mods. You need to be aware there are other steps related to the fcg in order to build a legal CETME rifle. There is the "shelf" that needs to be installed, "clipping and pinning" the lower, and making a stop for the selector so it will no longer rotate to the full auto position. Instructions for some of these steps are found elsewhere in this thread.


Section 922(r) U.S. parts count: You are definitely replacing 2 of the foreign parts that are counted when determining the legality of assembling a rifle that is considered "not suitable for sporting purposes." Those are the trigger and hammer. If the trigger bar is considered a "sear" by BATFE, you have eliminated another foreign part. I don't know how they rule on that.


btw I have never shot a CETME, or even held a complete one. It took me a while to realize that "fire" is the top position on the selector, and "safe" is the middle position, just the opposite of the HK G3/91.

I hope this is helpful to someone. :thumbup:

mitch/mike

[AMRifleman]

If you have a Cetme FCG that you want to mod, there is a good photo tutorial
on Weapons Guild. There may be one here too but I am new and haven't looked around much. From what I gather, there isn't much cutting done to a G3 FCG, there is the removal of a few parts, additional hole for hammer spring, additional hole to install and weld in a pin to limit the hammer from going into FA, the FA sear pin cutout/weld a shelf in. I haven't seen a tutorial yet on the G3 mod to SA. In the G3 the sear appears to be made together with the hammer but it can be un-welded and replaced individually.

[AMRifleman]

Not hammer spring, I meant to say trigger spring