DP series build sheet

These are the tools we used to accomplish the job at hand. You don’t
have to use these but we can’t adjust the build sheet to accommodate
any variances in tool choice.
Tool list by part to be modified:

Calipers in 0.001” graduations

Permanent Marker

Needle file set

Receiver:

Dremel tool or equivalent

5/8” diameter 3’’ long steel rod

Vice(Machine Vise recommended)

Drill Press(Bridgeport mill recommended)

5/32’’ cobalt drill

1/8’’ pilot centerdrill

10-32 tap

10-32 die

18’’ crescent wrench or suitable alternative

Dead blow hammer

Hardwood or aluminum block

Bolt Carrier:

¼’’ pilot centerdrill

3/8’’ cobalt jobber drill

½’’ 4 flute carbide Endmill with 0.03 corner radius

Bolt:

3/16” pilot carbide centerdrill

1/4” 4 flute carbide endmill std length

¼” 2flute SGS carbide straight drill

0.252” SGS double margin std. length carbide drill

0.250” SGS Extended double margin carbide drill

¼” Extended(3”LOC) carbide endmill

1/8” SGS straight 2 flute carbide drill

Lower trigger housing:

5/32” pilot center drill

1/8” carbide 4 flute end mill

#31 Cobalt drill(0.120”)

#13 Cobalt drill(0.185”)

0.1245” reamer

0.187” reamer

3/8” carbide 4 flute endmill

¼” 4 flute carbide endmill

DPM ONLY:

9/32” SGS 2 flute straight carbide drill

0.188” carbide reamer

 We’ll cover everything we can in this build and try to explain so that expert machinists and
laymen alike can come out with a functioning firearm. That said, we do most of our mods on
CNC machines and so there will be only pictures, diagrams, and explanations of these mods as it
would do you little good to see our setups and the machines running the parts unless you
possess the exact same equipment.

The only thing on the build that we WILL NOT explain how to do, is the head-spacing of the bolt
flaps to the barrel with gauges. This should be done by a COMPETENT gunsmith that
guarantees his/her work. This one thing can cause an otherwise functional gun to NOT work
and show symptoms that one might believe means it’s under-gassed, over-gassed, separates
case heads, etc.
 Receiver:

Whether you bought one of our receivers or have built your own, the fitment of the part is the
same(taking for granted that your weld-up was done correctly)

First, the dust cover. Oil or lightly grease the slot it goes in.

Next, if you bought one of our replacement dust covers, lay it in place.
If you are using the original, it’ll be necessary to bend it like ours’ in the picture to get it to go
in.

Now, using an aluminum or hardwood block(Oak, Maple, etc.) and a large hammer or mallet,
form the dust cover into place.
At this point, if the fit is too tight, use a brass drift or wooden block to push the cover into the
magazine window, and tap it “out” lightly up and down the length of the cover until it will move
back and forth in the slot with a bit of resistance( you want it to be a friction fit so it doesn’t
close on it’s own when the gun is tilted.)

Next, install the barrel retainer. It may be necessary on the new receivers to fit it a bit. See
below:
Next, let’s install the barrel shroud. Screw it most of the way on, then when it gets hard to turn
(about 10 to 15 degrees from straight up and down), put the 5/8” pin or rod in the gas tube as a
backer( to prevent crushing the gas tube), then using the big cresent wrench, finish tightening
the shroud being sure to check the alignment of the gas tube to the receiver, as shown below.

NOTE: If the barrel shroud screws on and stops before about 15 degrees off, then it may be
necessary to grind the shroud to allow it to go on further. If it over-clocks past the alignment
point, then you must decide whether to grind it enough to go around another turn, or build up
with TIG to make up the gap. Install your barrel and check against the shroud length to help
decide this.

When alignment is correct, gas piston/carrier should slide in freely into the receiver and shroud
assembly.
Once the shroud is in the correct position, you’ll want to make this permanent, using the center
drill, 0.156” drill and 10-32 tap, we can “lock” the barrel shroud position.
It can be ground like shown below.

At this point, try to install your barrel. If it drop right in, great! Go to the next step!

If not, how much is it off? A little off, say 0.010” to 0.100” can be adjusted by securing the
receiver in the vise, and bending the shroud with a deadblow hammer. More than that, and
you may have to heat the shroud with an Oxy-acetylene torch to bend it far enough. Take great
care in not getting in a huge hurry on this. This alignment makes the difference between a
quick change barrel, and one that requires a wrench and a hammer to change. Also, as
warning, do not heat the gas tube if heat is necessary. Only the barrel jacket. The barrel jacket
will bend without taking the gas tube with it since it’s only mounted at each end. If you bow
your barrel jacket, but not the gas tube, then it’ll be ugly but you can still make the gun work. If
you bow your gas tube it’ll have a friction spot in the middle of it’s traveled path and cause you
misery in the end.

Now for gas tube alignment. Install your barrel and lock it in place. Then install your modified
bolt carrier so that you can see the gas piston to gas nipple alignment as shown below.
It must align fairly close in both up and down and side to side planes. If it does, it ought to slide
up into place with ease. If the gas piston is resistive in the tube, you may adjust(bend) the gas
piston slightly to help this. If the carrier and gas piston go freely but the alignment is off, then
the shroud itself must be adjusted. Do this with extreme caution and usderstand that you may
destroy parts if you’re not careful.
With the barrel installed, if it’s side to side alignment that’s off, strike the side of the gas tube
with a deadblow rubber hammer until it lines up.

If it’s up or down that the shroud needs to go, with the barrel installed, using your wooden or
aluminum block place it either just in front of the gas tube(you will need to remove the gas
selector for this and front sight) and strike here using the receiver in the vise and the front sight
base as the backers or to go the other way, receiver in a vise, gas selector on blocks( you need
the gas selector installed for strength going this way) strike the shroud in the same area as
before but on the other side.
Do not move on in assembly until the carrier and gas piston are free with no
resistence and the piston slides up on the nipple freely.

Next, lets fit the ejector. If you bought a new receiver, check for a burr here:

If one is present get it out with the needle files.

Now look at the back of the pivot slot, if it’s squared out like below, move on, if not make it so
with the needle files.
Install the ejector and check for proper function. If you still have the original receiver pieces,
they can be used to check against.
Once it appears good, install the rear sight base and tighten the screw that holds it down. Now
check again for proper function and also try it with the bolt and carrier installed to make sure
that there’s no binding. If there is, additional fitting will be necessary.
Now let’s fit the lower. If you bought a new receiver, we made them a bit tight to accomidate
for the manufacturing differences in the original parts. An example of a tight fitting lower is
shown:

Grind where you must to get the alignment and fully closed position shown.

Such as here on the round tips at the front of the lower.

Or here, at the back of the lower on the boss that goes inside the receiver.

Or here, at the mouth of the slots in the receiver.

Your final result should look like this, with the lower droping in place without much resistance

And not having a gap between the bottom of the receiver and the lower.
Bolt:
Next we’ll attack the bolt and firing pin.

Cut the firing pin just ahead of the locking flap cam surfaces and grind them smooth as shown:
Next, using the tools perscribed, you are going to hole through the bolt from the side(1/4”
2flute straight carbide SGS drill) for the welded plug. Using cutting oil, and at about 1200RPM.

Clean hole out with rubbing alcohol, drive the plug in until it bottoms out, and TIG weld the
plug into the bolt with about 95amps and stainless steel 905 filler rod. Use compressed air to
cool the part imediately after welding(NO WATER QUENCHING AS THIS EMBRITTLES THE
PART!!!) until you can touch it without pain. Grind the welds to match original surfaces.

Now to drill the new firing pin hole. Base all of your feeds and RPM’s on carbide at 125 surface
feet per minute. The bolt is already hardened so this should be safe for the tools suggested in
the tool list.

From the center of the original firing pin hole on the bolt face, at a 7 degree angle is where the
new hole needs to be.
 Once you have it held at this angle in
your mill or drill press(mill is STRONGLY suggested on this!) Spot face a flat area as shown
above using the carbide 4flute ¼”regular length end mill. Then center drill the hole position.
Now using the ¼” SGS 2 straight flute drill, peck drill with oil as deep as can be done with this
tool. Switch to the 0.252” SGS double margin std. carbide drill and with oil, drill as deep as you
can again. Switch to the 0.250” SGS double margin extended carbide drill and drill down until
you almost are touching the back of the bolt face. Switch to the carbide ¼” extended endmill
and put a flat on the inside back surface of the bolt face for the firing pin spring to sit against.
Clean your hole out with compressed air and check fit your parts in the hole. The should go
with no resistance.

Now, using the picture below, spot face a flat sutable for drilling the pin hole. Then using the
1/8” SGS straight 2 flute carbide drill, peck drill with oil all the way through.

Install firing pin spring, firing pin and striker rod and use a slightly undersize rod or dremel bit
shaft to retain parts for fitting. Your needing to check firing pin at rest protrusion. It should sit
just below the face of the bolt:
If it protrudes past flush, grind on the tip of the striker rod:

Until it is correct.

NOTE: if you get too crazy and over grind this part, the firing pin will sit too far below the bolt
face and you’ll have a condition where the primers or the fired catridges will blow out and
and destroy parts inside the bolt with hot, dirty gases. The only fix is to get another striker
rod and try again, unless you’re really good with the TIG welder.

Once you have the length set, assemble with the provided 1/8”x3/4” pin. Test function and
check protrusion again to be sure.

Lower:

NOTE: On the DPM’s, you will need to weld up the original safety holes on both sides and grind
them flush on the outside and inside, to do you mods.

Using the provided blueprint and the suggested tools, mill out and modify your lower. The
safety and safety spring holes on the DPM’s are slip fit holes when finished. The sear and
hammer pivot pin holes need to be a minimum 0.0005” press fit when completed!
Once finished, if you have a DPM, take the safety, TIG up a tab and grind it to look like this:

This tab prevents the safety from overtraveling the detent plunger while in the “fire” setting.

Then, take the 0.188” reamer, and chase out the hole for the spring(shown at tip of file below)
and cut a clearance for the lever as seen in the same photo.
Install the spring:

Then the detent plunger:

Now blacken the back of the safety with the permanent marker, then install the safety in it’s
hole and work it back and forth a few times to score a mark:
Center punch where the end of the mark is:

And, using the 1/8” carbide straight 2 flute SGS drill from earlier, drill a spot for the detent to
rest:
Now intall the safety and check function using the plate provided with the 10-32x ¼” cap screw:

Put the left side grip panel on to see if you need to grind off some wood for clearance:
If so, grind it and touch up with gun oil to darken:
Now let’s fit the trigger. It starts out like this:

So install it using an undersized pin:

And grind and fit it until it clears the safety when it’s on “fire”:

And then grind and fit until you can engage the safety. This is an example of what it may look
like when done:
Now you can, at your option, dress up the trigger face for finger comfort like this:
Now let’s asseble the sear/disconnector with these parts:

The assembly looks like this:

Using an undersized pin, install it in the lower, then install the trigger. Check to make sure that
the sear touches the underside of the spring plate. It could look like this:

If so, remove it and grind here:

And re-install it. It should look like this:

Once that’s done, install the “helper” spring under the sear:
These two pictures show proper spring placement from two views.
Now you need the hammer, spring, and rod:
Install them in the lower using a undersized pin by placing the dome tip of the rod in the plate

Pocket, compress the spring and shove the hammer pivot down into place, and put the
undersized pin in place.
DO NOT check this function against any part of your body! This spring is very strong!

Check function against something “soft” like the edge of a 2x6:

Just DO NOT test against nothing, as it will damage this area here:
One it is working, put the lower in the receiver and screw in the take down lever to just past
parallel:

Mark the “locked” position and centerpunch it:

Drill the center punched hole spot with the 0.156” drill from earlier until the full diameter of
the drill is obtained. Then using a chisel punch, you can create the lead-out ramp to look
original:

Now to fit the disconnector. It starts out like this:

So, assemble you gun. Bolt in carrier, carrier in receiver, lower installed and take-down screw
in. pull the charging handle back until the carrier engages the disconector. You can see this
through the trigger hole on the underside of the lower. It shouldn’t be able to come all the way
to the rear without modification. We do this to allow variances. So grinding a little at a time,
you may end up like this:

Apply grease to the carrier and disconnector to prevent scoring the carrier between fitting
attempts. The gun should charge and cock the hammer, reset the disconnector without
“sticking” on the disconnector on way back to bolt closed position. If it does, take a wee bit
more off the disconnector. Brute force is NOT required to charge the weapon when things are
correct. Parts are made tough, but can still be damaged if not properly fitted.

Once the disconnector is fitted, your gun should bench test properly. Now you only need to
have the locking flaps fitted by a proffesional gunsmith to complete the build.

Some other notes:

If you’re using an original barrel, you’ll need to open the gas port in the barrel and the largest
gas selection on the regulator to 3/16” to operate the gun with the new setup.
Double check the spent cases during your initial test fire for ruptured primers from a firing pin
protrusion issue as noted earlier. A ruptured primer will ruin the firing pin spring and can cause
the firing pin to stick in the forward/fired position.

DO NOT dry fire the gun with nothing in the chamber as this can cause damage to the firing pin.
Use a “dummy” round with simulated primer for dry firing.

We usually hot blue ours but I have seen them parkerized before as well as ceracote finishes.

We will try to answer any other issues that you may have with an updated version of the build
sheet should it become necessary but please understand that “troubleshooting” your home
build is NOT part of the price you paid for this sheet and the parts. We also DO NOT warranty
home built or builds on our parts done by third party builders/gunsmiths.

The only warranty here-by implide, applies only to the parts we sold you against manufacturing
defects. It WILL NOT however, cover replacement costs of parts ruined, overground, or
otherwised rendered un-useable by the builder.

We hope you the best in you quest to build this awesome piece of history! Good luck & enjoy!