MG-42 BRP Build

Ask your build questions here. Welding, assembly, etc.
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 90 - 93
Attachments
90 - Cut 2 old pins to 13mm for assembling the front sight assy.
90 - Cut 2 old pins to 13mm for assembling the front sight assy.
91 - Assemble the sight assy using the short pins.  First I clamp the block in a vice to install the front sight.
91 - Assemble the sight assy using the short pins. First I clamp the block in a vice to install the front sight.
92 - Install the assembled sight assy into the receiver.  Drive the short pins out with the correct long pins.  Watch your alignment with your holes.
92 - Install the assembled sight assy into the receiver. Drive the short pins out with the correct long pins. Watch your alignment with your holes.
93 - Mushroom the ends of the pins.  I use a lady finger up against a vice on one side while I hit the other.  Don’t go crazy.  These pins will have to be removed to prep the MG for bluing after the test firing.
93 - Mushroom the ends of the pins. I use a lady finger up against a vice on one side while I hit the other. Don’t go crazy. These pins will have to be removed to prep the MG for bluing after the test firing.
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 94 - 96
Attachments
94 -  Drill out these rivet holes with a 3/8 drill bit.
94 - Drill out these rivet holes with a 3/8 drill bit.
95 - Install the front AA sight bracket.  Insert 2 of the small cut rivets from the inside. Weld the bracket on and grind flush.
95 - Install the front AA sight bracket. Insert 2 of the small cut rivets from the inside. Weld the bracket on and grind flush.
96 - Cut the heads off of 8 large rivets and 12 small rivets.  Grind the bottom of the heads smooth.
96 - Cut the heads off of 8 large rivets and 12 small rivets. Grind the bottom of the heads smooth.
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 97 - 102
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97 - Now you will set up the receiver to mill the rivet tooling indents.  You will need two different mills. A 3/8 mill and ether a 7/16 or a ½ mill.  I have seen both.  I like the 1/2 .
97 - Now you will set up the receiver to mill the rivet tooling indents. You will need two different mills. A 3/8 mill and ether a 7/16 or a ½ mill. I have seen both. I like the 1/2 .
98 - Start with the front AA bracket.  The holes are 28mm apart.  Use a 3/8 mill and only slightly mill it.  Less than .5mm
98 - Start with the front AA bracket. The holes are 28mm apart. Use a 3/8 mill and only slightly mill it. Less than .5mm
99 - Next do only the top and left side of the front barrel stop.  Measure back 7mm from the cut outs.  Center it with the cut outs.
99 - Next do only the top and left side of the front barrel stop. Measure back 7mm from the cut outs. Center it with the cut outs.
100 - Next is the top buffer tabs.  Measure 13mm and 30mm from the back of the receiver.  Center the holes on the top of the receiver.  Mill with a 3/8 mill.
100 - Next is the top buffer tabs. Measure 13mm and 30mm from the back of the receiver. Center the holes on the top of the receiver. Mill with a 3/8 mill.
101 - Next is the lower buffer tab and recoup stop. Measure 33mm and 60mm from the back of the receiver.  Center the holes on the bottom of the receiver.  Mill with a 3/8 mill.
101 - Next is the lower buffer tab and recoup stop. Measure 33mm and 60mm from the back of the receiver. Center the holes on the bottom of the receiver. Mill with a 3/8 mill.
102 - Measure out and mill the left and right rails.  Use ether a 7/16 or 1/2 mill.
102 - Measure out and mill the left and right rails. Use ether a 7/16 or 1/2 mill.
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 103 - 105
Attachments
103 - I use a Magna-Spot stud welder for attaching the rivet heads.  Any auto body shop will have one.  Make sure the brass parts are clean so you have a good ground on your receiver and the rivet head.
103 - I use a Magna-Spot stud welder for attaching the rivet heads. Any auto body shop will have one. Make sure the brass parts are clean so you have a good ground on your receiver and the rivet head.
104 - Only install 3 rivet heads now.  1 large rivet head on the top of the receiver for the front barrel stop.  2 small rivet heads for the right rear rail.
104 - Only install 3 rivet heads now. 1 large rivet head on the top of the receiver for the front barrel stop. 2 small rivet heads for the right rear rail.
105 - Place rivet head in the middle of the tool mark.  Put the stud gun over the top.  Press down on the rivet gun until the outer ground is against the receiver.  Push the button 3 times for 2 sec each time.  After the rivet cools take a pair of pliers to make sure the head is securely welded.  Install the other two rivets using this step.
105 - Place rivet head in the middle of the tool mark. Put the stud gun over the top. Press down on the rivet gun until the outer ground is against the receiver. Push the button 3 times for 2 sec each time. After the rivet cools take a pair of pliers to make sure the head is securely welded. Install the other two rivets using this step.
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 106 and 107
Attachments
106 - Place the lug on the bottom of the receiver over the front barrel stop.  Place one cut rivet on the inside and weld the lug to the receiver.  Grind welds flush.
106 - Place the lug on the bottom of the receiver over the front barrel stop. Place one cut rivet on the inside and weld the lug to the receiver. Grind welds flush.
107 - Align the rear sight bracket on the receiver.  Make sure the bracket is straight.  Place 2 cut rivets on the inside and weld the sight bracket to the receiver.  Mill the welds flush.
107 - Align the rear sight bracket on the receiver. Make sure the bracket is straight. Place 2 cut rivets on the inside and weld the sight bracket to the receiver. Mill the welds flush.
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 108 – 118 are for a bolt hold open lock. It is not original to the MG42. You can omit these steps if you like. I don’t like to smash my fingers.

Steps 108 - 110
Attachments
108 - Mark a line 12mm down.  Then draw a vertical line to square up the round rivet cutout.
108 - Mark a line 12mm down. Then draw a vertical line to square up the round rivet cutout.
109 - Mill out the area.
109 - Mill out the area.
110 - Mark a vertical line 3mm in from the cut.
110 - Mark a vertical line 3mm in from the cut.
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 111 - 114
Attachments
111 - Use a 1/8 x 3/8 key stock for steps 113 and 115
111 - Use a 1/8 x 3/8 key stock for steps 113 and 115
112 - Line up the key stock with the vertical line you marked on step 110 and with the horizontal line you machined out.  Weld the front to the ratchet plate only
112 - Line up the key stock with the vertical line you marked on step 110 and with the horizontal line you machined out. Weld the front to the ratchet plate only
113 - Cut the key stock flush with the notch you milled.
113 - Cut the key stock flush with the notch you milled.
114 - Grind the weld into a smooth ramp.
114 - Grind the weld into a smooth ramp.
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 115 - 118
Attachments
115 - Grind a bevel on one end of key stock.
115 - Grind a bevel on one end of key stock.
116 - Weld the beveled key stock onto the charging handle lock assy.  Only weld the top and sides.  Do not weld the bottom.
116 - Weld the beveled key stock onto the charging handle lock assy. Only weld the top and sides. Do not weld the bottom.
117 - Cut key stock flush with the bottom of the lock assy.
117 - Cut key stock flush with the bottom of the lock assy.
118 - Grind Weld smooth
118 - Grind Weld smooth
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 119 - 124
Attachments
119 - Lay out the holes on the ratchet plate.  Drill them out with a 3/8 drill bit
119 - Lay out the holes on the ratchet plate. Drill them out with a 3/8 drill bit
120 - Bend the stop tab up until it looks like this.  It can always be bend back down later if it is too far up.
120 - Bend the stop tab up until it looks like this. It can always be bend back down later if it is too far up.
121 - Install the disassembled charging handle into the receiver.  Align the ratchet plate.  The rivets should be centered in the cut outs and the center of the rivet should be almost level with the top of the ratchet plate.
121 - Install the disassembled charging handle into the receiver. Align the ratchet plate. The rivets should be centered in the cut outs and the center of the rivet should be almost level with the top of the ratchet plate.
122 - Move the charging handle to the rear of the ratchet plate.  Tack weld the ratchet plate to the receiver.  Only put one tack weld in the second hole from the rear.
122 - Move the charging handle to the rear of the ratchet plate. Tack weld the ratchet plate to the receiver. Only put one tack weld in the second hole from the rear.
123 - Move the charging handle all the way forward.  Weld a small tack in the first hole.  After welding ensure charging handled moves freely.  You don’t want it to tight or too lose.
123 - Move the charging handle all the way forward. Weld a small tack in the first hole. After welding ensure charging handled moves freely. You don’t want it to tight or too lose.
124 - Weld all the holes.  You want to have nice welds.  These welds do not get ground smooth.  After welding check to make sure the charging handle still moves freely.
124 - Weld all the holes. You want to have nice welds. These welds do not get ground smooth. After welding check to make sure the charging handle still moves freely.
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 125 -129
Attachments
125 - Lay out the trigger parts.  If your trigger assy is still assembled you do not need to disassemble
125 - Lay out the trigger parts. If your trigger assy is still assembled you do not need to disassemble
126 - Hold the grips up against the trigger housing.  Mark the grips where you need to mill them
126 - Hold the grips up against the trigger housing. Mark the grips where you need to mill them
127 - I screw the grip s down to a 2x6 to mill them.  Mill it very carefully.  I trial fit the trigger housing to check the cut.  Do not remove to much.  I use a ¼ mill
127 - I screw the grip s down to a 2x6 to mill them. Mill it very carefully. I trial fit the trigger housing to check the cut. Do not remove to much. I use a ¼ mill
128 - You should have a nice fit when you are finished.
128 - You should have a nice fit when you are finished.
129 - Assemble the trigger pack
129 - Assemble the trigger pack
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 130 - 135
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130 - Move the charging handle all the way forward and install the trigger pack.  The hammer must be down
130 - Move the charging handle all the way forward and install the trigger pack. The hammer must be down
131 - Move the charging handle back and check for interference with the front trigger pack mount.  Mark the interference
131 - Move the charging handle back and check for interference with the front trigger pack mount. Mark the interference
132 - Carefully release the hammer.  Don’t let it slam.  Hold you finger on it.  Mark where the hammer is on the charging handle.
132 - Carefully release the hammer. Don’t let it slam. Hold you finger on it. Mark where the hammer is on the charging handle.
133 - Remove the trigger pack and charging handle.  You must re cock the hammer to remove the trigger pack.
133 - Remove the trigger pack and charging handle. You must re cock the hammer to remove the trigger pack.
134 - Cut off the charging handle bolt tab at the hammer mark you made.
134 - Cut off the charging handle bolt tab at the hammer mark you made.
135 - Mill a notch in the charging handle bolt tab for the trigger pack mount clearance.
135 - Mill a notch in the charging handle bolt tab for the trigger pack mount clearance.
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 136 & 137
Attachments
136 - Assemble the charging handle.  Don’t forget the button on the end if you removed it.  This is the correct orientation of the spring in the lock bar.
136 - Assemble the charging handle. Don’t forget the button on the end if you removed it. This is the correct orientation of the spring in the lock bar.
137 - Install the charging handle then the trigger pack.  Check the clearance between the charging handle tab and front trigger mount and also the hammer.
137 - Install the charging handle then the trigger pack. Check the clearance between the charging handle tab and front trigger mount and also the hammer.
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 138 - 142
Attachments
138 - Remove the trigger pack.  Push the charging handle all the way forward.  Measure the distance from the charging handle bolt tab to the front of the ejection port. (138F)  Mine is 8mm
138 - Remove the trigger pack. Push the charging handle all the way forward. Measure the distance from the charging handle bolt tab to the front of the ejection port. (138F) Mine is 8mm
139 - Measure the distance between the front of the charging handle push off bar and the ratchet plate. (139G)  Mine is 5mm.  Subtract 138F – 139G = (139H)   Mine is 8mm – 5mm = 3mm.  This is the how much needs to be cut off of the ratchet plate.  Measure in 139H on the ratchet plate and mark it.  Now measure from that mark to the front of the ratchet plate. (139I)  Mine is 17mm.  Cut a piece of Key Stock to the length of 139I (same key stock that was used in step 111)
139 - Measure the distance between the front of the charging handle push off bar and the ratchet plate. (139G) Mine is 5mm. Subtract 138F – 139G = (139H) Mine is 8mm – 5mm = 3mm. This is the how much needs to be cut off of the ratchet plate. Measure in 139H on the ratchet plate and mark it. Now measure from that mark to the front of the ratchet plate. (139I) Mine is 17mm. Cut a piece of Key Stock to the length of 139I (same key stock that was used in step 111)
140 - Slide the charging handle back until it is 10mm from the back of the receiver.
140 - Slide the charging handle back until it is 10mm from the back of the receiver.
141 - The end of the charging handle if exposed in the receiver cut out.  A small piece of metal will be welded in to fill this area to prevent the charging handle from jumping out.
141 - The end of the charging handle if exposed in the receiver cut out. A small piece of metal will be welded in to fill this area to prevent the charging handle from jumping out.
142 - Measure this distance (142J) Mine is 6mm
142 - Measure this distance (142J) Mine is 6mm
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 143 - 146
Attachments
143 - Lay a short section of key stock on the bottom of the receiver next to the ratchet plate tab.
143 - Lay a short section of key stock on the bottom of the receiver next to the ratchet plate tab.
144 - Now mark the ratchet plate tab ½ way between the thickness of the key stock you placed there.  Cut the ratchet plate tab off at this mark and the one from step 139
144 - Now mark the ratchet plate tab ½ way between the thickness of the key stock you placed there. Cut the ratchet plate tab off at this mark and the one from step 139
145 - Measure this distance (145K) Mine is 11mm.  Cut a piece of key stock to these measurements: 142J x 145K  Mine will be 6mm x 11mm
145 - Measure this distance (145K) Mine is 11mm. Cut a piece of key stock to these measurements: 142J x 145K Mine will be 6mm x 11mm
146 - Take the piece of key stock from step 139 and mark out a notch 3mm x 142J
146 - Take the piece of key stock from step 139 and mark out a notch 3mm x 142J
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 147 - 152
Attachments
147 - This is the way they get put together.
147 - This is the way they get put together.
148 - Install these 2 pieces into the receiver and weld.  Do not weld the side closest to the trigger pack cutout.
148 - Install these 2 pieces into the receiver and weld. Do not weld the side closest to the trigger pack cutout.
149 - Grind welds smooth. Don’t grind the weld on the front.
149 - Grind welds smooth. Don’t grind the weld on the front.
150 - Install charging handle and push it all the way forward.  Mark the area where the push bar hits the new receiver/ratchet plate area.
150 - Install charging handle and push it all the way forward. Mark the area where the push bar hits the new receiver/ratchet plate area.
151 - Grind out the marked out area.  Reinstall the charging handle.
151 - Grind out the marked out area. Reinstall the charging handle.
152 - Check the charging handle stow lock.  You may need to mill the front of the ratchet plate back to get it to lock properly. Check the clearance between the charging handle push off bar and the receiver.  You may need to cut the push off bar down
152 - Check the charging handle stow lock. You may need to mill the front of the ratchet plate back to get it to lock properly. Check the clearance between the charging handle push off bar and the receiver. You may need to cut the push off bar down
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 153 - 157
Attachments
153 - Assemble the bolt assy.  Install the bolt in the receiver.
153 - Assemble the bolt assy. Install the bolt in the receiver.
154 - Mark the semi auto receiver block where the rear of the bolt hits it
154 - Mark the semi auto receiver block where the rear of the bolt hits it
155 - Mill the semi auto receiver block.  Remove as little as possible
155 - Mill the semi auto receiver block. Remove as little as possible
156 - Reinstall the bolt and check the fit of the charging handle tab on the bolt tab
156 - Reinstall the bolt and check the fit of the charging handle tab on the bolt tab
157 - Install the barrel, trigger pack, recoil spring, and buffer assy.
157 - Install the barrel, trigger pack, recoil spring, and buffer assy.
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oakrodent
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Re: MG-42 BRP Build

Post by oakrodent »

Steps 158 - 161
Attachments
158 - Watch the rear of the bolt as you pull the trigger.  Ether you should see the bolt move back or the hammer will hang up.
158 - Watch the rear of the bolt as you pull the trigger. Ether you should see the bolt move back or the hammer will hang up.
159 - Remove the bolt and disassemble it.  This is the area that needs to be milled.  Mark a line 40mm from the back of the bolt.
159 - Remove the bolt and disassemble it. This is the area that needs to be milled. Mark a line 40mm from the back of the bolt.
160 - Set up the bolt in the mill at a 40 angle.  Mill the bolt up to the line you marked.
160 - Set up the bolt in the mill at a 40 angle. Mill the bolt up to the line you marked.
161 - Your bolt should look like this.  Reassemble the bolt and install the bolt, recoil spring, and buffer assy.  You will need to depress the hammer to slide the bolt head over it.  Check the clearance of the hammer and the back of the bolt by pulling the trigger.
161 - Your bolt should look like this. Reassemble the bolt and install the bolt, recoil spring, and buffer assy. You will need to depress the hammer to slide the bolt head over it. Check the clearance of the hammer and the back of the bolt by pulling the trigger.
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Re: MG-42 BRP Build

Post by oakrodent »

Finial 3 Steps 162 - 164
Attachments
162 - Remove all major parts
162 - Remove all major parts
163 - Attach all the remaining rivet heads using the stud gun.  3 large rivet heads go on the buffer tabs.  1 large rivet head goes on the recoup stop/ trigger bracket.  1 large rivet head goes on the left front barrel stop.  8 small rivet heads go on the rails.  The last 2 small rivet heads go on the front AA sight mount.
163 - Attach all the remaining rivet heads using the stud gun. 3 large rivet heads go on the buffer tabs. 1 large rivet head goes on the recoup stop/ trigger bracket. 1 large rivet head goes on the left front barrel stop. 8 small rivet heads go on the rails. The last 2 small rivet heads go on the front AA sight mount.
164 - Clean all parts and the receiver.  Wipe everything down with an oily rag.  The gun is now ready for reassembly and test firing.
164 - Clean all parts and the receiver. Wipe everything down with an oily rag. The gun is now ready for reassembly and test firing.
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Re: MG-42 BRP Build

Post by DougF »

I can't thank you enough for going to all of this trouble for us new guys. You're a great man.
sfso08
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Re: MG-42 BRP Build

Post by sfso08 »

This will help greatly with my build. Looking closely at your trigger pack I see that it isn't the regular AR15 profile. It appears you used part of the original trigger to cover the AR15 trigger. Would you share with us how you did this?

Thanks
Robert
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