What I can gather from it all if you notice the silver block behind the trigger. I believe works as the safety buy moving left-right and stopping the cocking handle notch and will prevent the FA bolt from sliding in that’s why the sear is gone and the cocking handle catch has been moved to the far right rather then running the original width of the pad. And according to the installation manual says to install the bolt before installing the trigger housing.

I originally was under the impression that BRP moved the rails inward a few thousands, but the bolt head appears to be unmodified. The: AK-47, AK-74, FAL, G3, Cetme, AR-15 and MAC series (just to name a few) have nothing that prevent the FA bolts from being installed and these were approved for mass retail.

Just a note:

I spoke to Brian at BRP Guns and asked to purchase an MG42 semi-auto bolt.  He replied after a week or so and told me NO PROBLEM!  He said that he has a limited supply of bolts and parts right now but they would be available at a later time!  I then asked if I supplied the bolt could he do it, again he replied and said yes.  If I sent him my bolt he would do it for $250.00.  Remember you must supply the bolt!

$250.00 to me is a very fair price!  There is a lot of fabrication involved and if you screw up you can ruin the bolt and will have to start from scratch. 

I am not going to purchase one at this time but I did want to share the info with the forum!

The MG42 Semi-Auto bolt is the heart of the semi conversion and can only be done with a mig welder and a lathe to fabricate the extension and the dimple recess to allow the spring to seat in the rear of the bolt!

The pistol assembly is a little chore but can be done in the basement as well as the rest of the project!

If any one attempts the project remember to modify where the pistol mounts to the receiver as a priority!  The original pistol assembly must not be able to be mounted in the semi-auto and modifying the receiver to not accept one is a big step in avoiding the accidental fabrication of what the BATF may interperate as a machinegun!  Having a spare STRIPPED Full Auto pistol grip on hand would be a good idea to show if it was ever questioned.  This would cover your ass in the "intent" dept!

This is a do-able project by anyone who considers himself a hobbyist!  It may not be as pretty as BRP's but I am sure it is possible.   A Lathe, Drill Press, MIG Welder, Bench Grinder/Wire Wheel,  Die Grinder/Dremmel, should be all you need...maybe a Mill but not necessary.  You can get a mini lathe for $300.00 bucks (Harbor Freight Tools).  It may come in handy to fabricate the firing pin also but I am not positive of that!

Good luck and if any questions let me know I have put forth a lot of thought into doing this project and would be glad to share any info with anyone interested!  I will do this!

I was told by others that Brian at BRP is a good guy and I am sure that he knows that his design will be copied by others.  As long as no one is selling his design there should be no problem!  It is perfectly legal to build your own rifle and that is all this is!  I do stress that the receiver must not accept an original grip stick.  The new grip stick must be modified to no longer accept the drop down sear.  Cutting the area out and then welding plates on it with the pin holes for the AR15 trigger and hammer does accomplish this! 

Remember this is a home build and copying the design not for resale is legal.  I personally would not condone any Class 2 copying this and selling them because that is illegal and morally wrong!

I have 90% completed the Grip assembly and it works well.  It is not an exact copy, I actually did it slightly different and am currently working on the "safety" which I will complete in the next few days but the rest works fine.  Trigger, disconnector, and the hammer.  The disconnector has to be "smithed" a little bit to catch the sear when released.  The hammer must be "smithed" alot to allow it to fall deep enough for the bolt to pass over rearward and FORWARD!

I only have the section completed where the grip stick mounts and sliding  the bolt on the rails just on this section.  Once I feel it is good I will weld the next pieces of the receiver together.  Once I get the safety done this will no longer accept Full Auto bolt or sear parts and it will be OK to complete.  The stock bolt sear catch cannot pass over the hammer there is not enough clearance that is why the new bolt has the catch to the side where it cears the hammer by about 1/8".   This will not allow FA parts therefore it is OK to continue!

anyone got pics of the housing where the trigger housing goes?

I will post some pics  hopefully by tonight.  I used a piece of angle iron in front of where the hammer is when in the up position that catches the receiver where the dust cover slot is...this is why dust covers are not used.  The area ON THE RECEIVER where the original grip catches (the front part not the pin) is ground away as much that is needed to not allow it to catch anymore!  That is in a nut shell there is more to it but not much...the pics I will post later will show more clarity!

Here are some pics of the trigger housing please excuse the roughness and the bolts and nuts that are temporarily holding the hammer and trigger in place.  Note:   If you are familiar with the AR-15 trigger and hammer you can see the mods they needed to create the clearance for the bolt...even the disconnector was slightly filed on top.  This new trigger group functions flawlessly!  It fits so nicely into the receiver it's scary!

The only draw back is I have not incorporated the original trigger.  It is hollow so maybe I can modify it to fit over this one....we'll see!

Here is a better shot to see the new mounting on the front to catch the receiver.  Please note the previous shot that shows a stock MG42 Grip to compare with this

This is the area ground away (below) that shows a stock mg42 grip (top) cannot be utilized in the semi-auto.  It can pin in the rear but the front catch has nothing to grab onto!  This must be

Here is a good shot of the semi auto grip from the front....this shows the new "L" bracket and how it catches the receiver from the ejection port area....this is the reason why the dust cover can not be utilized......yet.....until one of us figures out how to modify it!

It looks like the cocked hammer is tight in that area but I assure you it is not and it functions perfectly!

Here is the grip in place and snug as a bug in a rug!  Also a shot  from the top of the receiver looking in!  That patch of metal in between the ejection port and the grip thru-area is not seen (it may look like one big opening but it is not) because the new grip "L" mount is cupping it!  It really fits in there perfectly! 

Please note to all that may not be aware.....the ejection of mg42 shells pass through the bottom of the receiver not the side!  Just in case anyone was confused when I was referencing the "ejection area".

It is very close to the BRP but not identical.  I am not making it to sell so it does not need to be inspected by the ATF but it must fall under their rules (they interpret NFA and GCA). 

I have not seen the BRP first hand but this design that I am doing has fallen into place with the BRP. 

For example I had to modify the bolt almost exactly as the BRP otherwise it will not pass over the hammer.  You need to mill/grind off the sear catches and then create a new one that is off to the side.  I have not done the extension yet!  My new sear catch interfered with the recouperating spring housing on the short side.  I rectified this by just grinding it down alittle bit to allow the sear catch to ride right over it.  This in no way affects the operation of the recouperating spring!

I had to shorten the Charging Handle just like the BRP or, just like the bolt, it will not go over the hammer...instead it passes by the side of it!

I am not sure exactly how BRP catches the front grip onto the receiver but what I did works great, it may be the same as BRP (it looks similar) but I really am not sure.

BRP has an aluminum or silver piece of metal in the upper part of the grip and some claimed it prevents the sear catch on the full auto bolt from passing.  I do not think that is its function.  The Full Auto bolt can not clear the hammer so it is not necessary to have it for that reason......I think it is connected to the "safety" lever that is below it.   I do not know.  I made my own piece that fits in there and it does function as a safety and works!  It is only used if the hammer is cocked and will not allow the trigger to be pulled.   I am pretty sure the BRP does the same as mine, if you look close at the picture of the BRP zoom in and note that it has room to move to the left to coincide with the lever that is below it.....the BRP I think just uses a nice piece of metal that has been milled on the inside.  This milling is out of view on the photo and I believe it lines up with the trigger and the safety lever! (very hard to explain...easier if you have grip frame apart to look at pieces).  I am not finished but I do have a good start and will post more pics as I finish it up!

That would be good for the dust cover.  Note:  The dust cover is tripped by the bolt catch.  The bolt catch is milled off and relocated on the semi!

The grip interferes with it now because of a new mounting design but the dust cover can be shortened and  fit  with a new mounting hole or two.  Just tripping it seem to be the big problem for me!

I would like to hear your idea, I am sure it can be figured out!

I will try to explain it.

On the receiver floor on the same side as the new bolt catch, drill a small hole and rivet in a arm that will reach over and just bump the latch open on the dust cover when the bolt is in battery. You will use the shortened cover as you stated and the new charging handle catch is what bumps the arm.

I like the idea and that is the type of idea that has to be fabricated to make it work.  I understand the concept but I just cant visualize it enough to make it happen in my head.  Maybe when you get time you could scan a drawing like you said.  Thanks for the help!

FV

For everyone who bought a kit and want to build it please click on the following link and scroll down to the bottom of the page.

http://www.blackrivermilitaria.com/other.html

Have your trunnion in your hand for comparison. The wear is supposedly attributed to the recooperator springs so you may want to buy new ones and a new trunnion if your trunnion is trashed BUT in my OPINION it may not be necessary for semi auto as you won't be running at such a high cyclic rate anymore.

I thought about it and the trunnion is a pretty hard part so it probably won't be very effective to try to rebuild the stops with weld and machine to configuration so a replacement will probably be neccessary if yours is bad.        

If you want to run a crankfire on this then you may want to fix this part.

Yes,  BRP did update his site and dropped some photos of the Semi Auto.  I think those were work in progress anyway and not his final work.  As long as you can get an AR15 trigger group the rest is just making it work and all the rest is posted on this site!  I do not think BRP is worried about Hobbyists copying his design I think his site was just due for updating.  Besides he claims he is just making 250 of them. 

I know if I was someone who could spend 4 grand on one of these I probably would be the same type of guy who would not have the skill to build one!

Anyone building one of these in your basement for yourself and NOT for profit poses no threat to BRP!

Here they are, I have them on my hard drive plus I burnt them.

What AR trigger parts do I need?

Hammer, trigger, disconnecter, trigger spring, hammer spring and retaining pins.
Basically all the AR fire control, Sometimes I have found M-16 trigger parts cheaper , you could also use them.


Here is a pic. You don’t need the 2-stage but it was the only picture I found quick. Plus the retaining pins.

http://www.bushmaster.com/shopping/dcm/8448592-scgk.asp

Also you dont need the safety selector as pictured. Cost is right around 30-40$
 

 I used a lenth of 3/4 in black pipe and  drilled a 7/8 hole 3/16 into the end sawed it lenthwise opened it up to the right dia. for the bolt extention until i get acess to a lathe. o1 tool steel will make a nice firing pin easy to heat treat to. I used a roller berring on the transport pin. I think thats what brp did. this company has tool , steel, pins ,rivits ect fast shipping http://www.mcmaster.com/

How you guys utilizing the original trigger? 

Probably help if open up my trigger group but I think I'm going to watch from the peanut gallery for a while.

You smart guys feel free to post an occasional pic for us non-smith types.

Next question:

Why relocate  the trigger housing forward and interfer with the ejection port?  

 My idea is to build up the reciever thickness on the front of the opening for the trigger housing.  On the trigger housing itself I'll open the gap in hieght and length.  This would prohibit the installation of a standard full auto trigger housing.

You may have a problem with the "readily restorable" part.  If you are able to just file down the spacer and it's ready for a FA trigger housing to swing on then you may want to incorporate something else to prevent installation of a FA trigger housing. 

Then again......Maybe it would fly!!!!!!!!!!!!!!!!!

Yeah, I was wondering if that would be enough.  I'd think you could go farther by filling part of the rear trigger-frame opening on the reviever and welding a post on the reciever that would require a hole drilled into the top rear of the frame. 

Here is a pic of the latest mod to the front of the grip stick.  This accomodates the dust cover latch mechanism that locks it into place.

It serves 2 purposes:

1-inside it catches the receiver.

2-outside it catches the dust cover latch.

Here is what I did to the bolt catch.  This "kerf" aids in knocking down the dust cover as the bolt passes over it. 

I really dont want to sound like a jackas- here, but don't you think that the problems of the poor parts fitting ,"trigger slap"  and the broken firing pin issue should have been resolved BEFORE this person started taking money for a product that had known flaws and were sold anyway?I don't think anyone should lay out a pile of cash and recieve a product that needed eight hours of work to function as it was sold.I agree the recievers are a work of art but the rest of these guns needs to be better built and have more care put into assembly. The basic concept of this semi conversion is sound but the execution should be dont better.Just my two cents worth.  

What I'd like is to find someone to reweld my receiver to semi configuration. I think I can handle the trigger group and the bolt conversion but jigging up and welding the receiver so it's straight I think is rather over my head.

It is really a shame that there is all kind of "little issues" with the BRP.  On the other hand it does make me feel better that I have had similar issues building mine!

I could not even estimate the hours I have put in making everything work properly.  The mods to the trigger group with the AR15 parts was nuts, then the dust cover mods, and then there were other parts like the Barrel Change Door that was just too tight to the Barrel when closing.  I had to just take a "c" hair off the stops to make it open and close AND let the Barrel rest in the trunnion with the proper tolerance to allow the action and the recuperating spring do its job.  I guess it was barely off from the reweld, probably anyway! 

I am very pleased so far but I know I may redo the trigger group.  It is good but not perfect, it does function very well though!  I still have to finish the bolt extension and fabricate the firing pin.  I hope to finish in next week or two.

Like I said before there were many smithing issues that needed to be fitted and then refitted and refitted until perfect, I guess this is why BRP owners have had some problems.  I agree with the idea that $4500.00 should buy you a tested and great running gun!

I have heard from a few owners that have all said the same thing,  Broken firing pins with less than 40 rds or so run through them!  Unfortunately that tells me the guns were not tested properly.  The cheapness of 8mm ammo and the ease of running a 50rd belt through the gun leaves no excuse for this to happen.  If these guns were tested properly a few hundred rds would have been run through them and the problems would have been resolved by some "smithing" on the bench at the shop.  That is reality.  I do love the BRP and have heard good things about Brian.  I am also sure he will make good and resolve any problems that arise.  The only problem I see is that the process is frustrating.  To all the owners remember.......you have an investment in the BRP....it can be resold in the future since it is a registered firearm made by a Cl2 manufacturer. 

thanks 81,

       mg34ss wrote       The gun had severe "trigger snap" 

What do you mean by triggger snap ? is that annoying pounding that you receive when the bolt recoils against the hammer and transfers to the  triggger.

and just out of curiosity  if you hold the trigger while cocking the weapon  (all the way back so the sear disconnecter is holding the hammer ) and then ease the bolt  forward ...does the hammer ride  on ,or come in contact with the bolt bottom on the forward stroke ?

I ask this because occasionally my disconnecter fails to hold the hammer back

Thanks guys

When I started to do the trigger group modification I found the trigger had to be mounted quite low in the grip frame to prevent the hammer from "bottoming out" on the disconnector and the trigger during the bolt travel. The hammer is actually being thrown down as the bolt travels to the rear. I am posting pictures of my grip frame and you can see how the trigger is visable in the trigger opening. Also included are better(better camera equals better pictures) pictures of the bolt group.

mg81

The striker sleeve (that carries the firing pin) must be drilled out to allow the full length firing pin to go through it.  I seem to be having a problem drilling through it.  I am using my mill/drill at different speeds with and with out lubrication...basically I have tried all I know.  It is obviously hardened steel.  do you or any one else have a suggestion on how to drill through it???  I am asking you since you have already done it but if anyone else has a suggestion I am all ears...Thanks in avdance!

FV

ScenarioL113,When I drilled this part I used a solid single flute drill bit . I got it ffrom a place called MSC. The phone number is 800-645-7270.I do not remember the exact size right now but the drills you need are listed on page 115 of there catalog under"Solid Carbide 2 Flute  140* Straight Flute Drills" on the top of the page. A strong word of caution these drills are MEGA fragile you must use them in a mill with the tables clamped down solid as the drills do not flex at all,if you drop it to the floor chances are you just broke a chunk off it, but they will drill a hole in a file. Run the drill dry and slow clearing the chips often and when you break throught the casehardened skin you really must be carefull not to let the soft chips from the core bind the drill or it will snap off.They are somewhat of a hassle but when all else fails they always work.The web address for MSC is "mscdirect.com".

Thanks I am using a mill and will give it a shot. 

Did it require a lot of force to draw it in to get it started? 

Is it hard like that all the way through?

scenarionL113, No the carbide drills do not require a lot force for them to cut . The locking wdege is case hardened so it is much harded on the surface and softer in the core. The wedge is not soft like mild steel inside but it is no where near as hard as the surface.

mg81,

One more thing, at what rpm would you think to run the mill at???....about???

Thanks again!

scenarioL113, I used about 900rpm on the surface and slowed down to the area of 550-600 in the core becuse the chip builds fast and the drill has a straight flute and will not clear itself.

MG81,

I got the bit and drilled at about 1000rpm on the mill.  I can not believe how nice that carbide drill bit did the job!!!! Thank you very much!

Anyone attempting to drill thru the striker sleeve, the special drill bit posted above works awesome!  Set it up in a drill press or a mill and just used light steady pressure.

My 42 should be done in maybe another 2-3 hours worth of work tweaking at the bench!

I made my bolt extension slightly short and have to weld a little extra more on to it!

I miscalculated for the extra travel that the "hammer" needs when it falls from the bolt going over it!  The falling hammer needs about 1/2" additional clearance.  I can not believe I made such a stupid mistake!!!  I was having trouble holding it together in the receiver without it being welded together, I thought it was good and welded it.  The hammer just barely catches the spring when the bolt travels back forward and hangs up on it.  Another 1/4" and it would have been fine!  I will add 1/2" just to be sure!Now I have to add an extension to the extension.  It really is no big deal and it will come out fine but it will not be perfect, Oh well! 

Please heed this post to all our homesmiths!  Your mg42's will be slightly different than eachothers and exact measurements may need to be compensated in all aspects and steps of this build....Good Luck Everyone! 

Ahmen brother I did the same  thing an extension for the extension took me two tries and I'm still not sure i like it. it got beat up on the rear cover, the spring compresses when the bolt hits it breaks firing pins etc. I made a solid one just took it apart and replaced the spring with 1/2 black pipe and sleeved it to make up the i.d. difference

see post for possible firing  problem 5 or 6 th one down

  /www.weaponeer.net/forum/forum_posts.asp?TID=461&PN=1&am p;TPN=1

Smithy; I have a question,when you say that "when the spring compresses it breaks firing pins" Are you refering to the spring on the buffer in the butstock? If you are you may want to rethink your elimating of the spring on the buffer. The buffer is the "last stop" for the bolt assembly. The spring slows the bolt to a stop slowly (sort of) and gives it a kick back forward. The spring on the buffer will also stop the buttstock lugs from battering your reciever to death . The recievers are just mild steel and do have much ability to withstand the battering of a solid buffer assembly.You can drill a counterbore in the center of the bolt in the buffer and the firing pin will have no contact with the bolt as it recoils. I had problems with my gun's bolt hanging up in the rear most position after firing it  and I traced the problem to the fact that my reciever and stock assemby were not all that tight anymore and the stock woould move to the side during recoil and the bolt extension would hang up in the tube.I elimated this by making an intermediate shuttle piece for the ejector, you can see it in the pics I posted it is the part that fits into the rear of the bolt with the small set screw above it. When I made this part the bolt hang up problem was gone and the gun fired much smoother as the bolt now did not have to telescope over the buffer assembly.if you would like I will post a pic of my buffer assemby dissassembeled  for a view of the components.

Anybody have problems with the firing pin not hitting the primer hard enough to make it go bang!

I am testing mine and have experimented with a few firing pins all different lengths (the differrences are minimal for testing only).  No matter what I do it seems the hammer is not striking the pin hard enough.  I put the bolt in a vise and strike the pin with a hammer and it fires off the primer (that tells me the firing pin is atleast ok where it makes contact with the round). 

My best estimate of where it comes thru the rear seems to be good (this is why I have made a few at different lengths).  As far as I can see the hammer is making contact.  The rounds end up having a small dent  (maybe 1/2 as deep as should be).

I do not know?????? Do they make heavier springs for the hammer??????

Maybe your hammer is too light? Might try building it up with weld to get some more weight?

EZFEED

I had thought of that and I will try it.  I did grind a good portion of it off and probably too much.  I would not of tried it if you did not suggest it, thanks I will let you know.  It may be a few days, thanks!

Brownells (1-800-741-0015) has "extra power" AR15 hammer springs.Part number 969-000-100 for $4.99.

OK guys, I'm thinking outside the box here so I'd like to kick an idea around. It seems like the norm is to use AR trigger parts but since this thing is not considered a semi "assault rifle" subject to 922r because it does not feed from a spring loaded magazine I wonder if anyone considered using a FAL trigger system. Quality parts and anyone who has made a FAL type or two usually has the trigger, sear, hammer, safety and trigger spring already laying around. I think the front of the Mg42 trigger group could be adapted to the FAL type big pin and the front is already there in the front of any FAL type crapped out lower. The front stud attachment is on the middle of any FAL type cut receiver, a part that many of us have laying around too.

Any of you guys who may have some FAL stuff laying around take it out and compare it to A: the pics of ak47 Dennis's photos of his trigger group further back in this thread and B: your own Mg42/1/3 pistol trigger group and see what you think.

  Another suggestion that was told to me by another,, What about using an already approved complete trigger group/ i.e. something like a CETME or G3/91 group. I don't have one handy to compare to the bottom of my cut Mg42 receiver but that also maybe another alternative.

  Posistion of the hammer to time square (or close to square) with the new firing pin is something that will have to wait until I get a modified bolt in a legal rewelded receiver but I think an alternative trigger group can be done and the ATF boys may like it.

mg81 Iam trying to build a rear cover type R  number 2 which is solid I believe. Also I opened the booster cone to 1/2" to ease the recoil as I am still having problems with dis connector not staying cccconected ahas would be appreciated 

smithy; I see your line of thought here. The solid buffer was/is the slower of the two in the full autos.Even with the slower rate of fire the mg42/mg3 is a violent one when it comes to the velocity of the bolt and carrier. When you say that you are having problems with the disconnector holding my thoughts would be what is the hole spacing you used for the trigger and hammer pivots and what is the angle of the trigger to the hammer as the hammer is cammed back by the bolt if the trigger drops to far down you will have problems.Please don't take this in the wrong way but I know when I built my 42 there was more than once that I got buried in a problem that turned out to be simple in the end.One of those "can't see the forest through the trees" kind of things. As to your disconnector you may have to dress down the forward nose of it to get more engagement with the hammer, this is not an uncommon thing to do on AR rifles due to the tollerances alloted by  the many parts suppliers. 

smithy; one more thing I thought of if you can see in there at all make sure the hammer is not being cammed back (down) so far that the tail end of the hammer is hitting the disconnector and pushing the disconnector into the released position. If all else fails Brownells(1-800-623-3896)sells a AR stlyle trigger group that uses a Garand/M14  style sear and disconnector the sear and disconnector surfaces are located above the pivot pin hole .This style of trigger would definately be easier to work into this application. The part number for the trigger set is 739-000-001 price is $120.00, kind of spendy but it works great.Hope this might help you out a little.

Here some close up of the fire control. The trigger is standard AR, the disconnecter and hammer have been modified. Sorry for the poor pictures my camera old! I need to stop buying parts kits and get a new camera.

The stock disconnecter is on the bottom

Original disconnecter and trigger

New made disconnecter and trigger

I wanted to ask you a question I had forgot, Dennis is your trigger centered in the pac? or off to the right side to bypass the lug on bolt and legal begal rivet in back of recieverto keepout full auto bolt? Also would you have an extra trunion pin to sell? need one....ah the wait but maybe one will turn up. slowfinger

Yes the trigger is centered, the auto sear is removed and the cocking lug needs to be moved for hammer clearance. Take a look a some of the pictures I posted of the bolt. I have a big rivet in the back of the receiver to prevent the FA bolt, as far as the rivet it came with my new trunion from RTG parts.

Can you post some pictures of your TNW 34 this would help tremendously?

This is my trigger group, I have made 2 like it using all original AR15 parts with no mods to the trigger, disconnect, the only thing I have done is to build up hammer with weld being as I set it as low as I can in grip frame. I milled out the grip housing completely with just the sideplates I had put on for the new locations. So far it has worked well with no Breakage or issues

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