About the AR15  
 

Instructions for completing an PCR 80 AR-15 receiver with the BAXTER

ALWAYS Keep the Baxter in a fixed position with clamp or vice!!

If you are using a TI, AL or BRZ casting rather than a forging – the top surfaces of the receiver must have the cast surface filed, milled or worked spec. to print dimensions before beginning the process.

Cast Titanium Receivers have stock on the” upper” interface & require milling as well as the buffer tube: must be machined / milled to spec before proceeding. Titanium REQUIRES low feed and speed with plenty of coolant (do not drill, mill or machine without coolant).

 

Follow for instructions and pictures READ AT LEAST THREE TIMES!  TAKE YOUR TIME!!

"Mounting" the receiver into the BAXTER drilling fixture.  The following operations are assisted by the jig.  Using the BAXTER, you should be able to handle these operations. A mill is optional – not required. See options below

  • Front pivot pin - hole drilled with 1/4"

  • Rear takedown pin - hole drilled with 1/4"

  • Trigger pin - hole drilled 5/32

  • Hammer pin - hole drilled to 5/32

  • Selector - hole drilled to 3/8

  • Bolt hold-open plunger drilled with 5/32" to a depth of .470"

  • Trigger guard - left side - drilled with 1/8" through both ears

  • Trigger guard - right side - drilled with 1/8" through only one ear

The next group of operations - measure and mark before drilling.  The fixture assists in these operations by giving a means of securely locking the receiver into one fixture on your work surface.

  • Front pivot pin detent - hole drilled with 3/32" to 1.125" deep

  • Rear takedown pin detent - hole drilled with 3/32" through to detent pin hole

  • Selector detent - drilled through to selector with 1/8" then countersunk with 5/32"

  • Bolt hold-open pin - hole drilled to 3/32" with 6" aircraft bit

  • Stock index hole - drilled with 1/2"

  • Grip hole drilled - with 7/32"

  • Buffer stop plunger - hole drilled with 1/4" to .712" deep

The BAXTER lets you clamp the receiver safely within a vise or to a work table while performing these operations.

  • Fire control well milled -by .030 with a 3/8" end mill- option shave down your parts to fit the pocket.

  • Rear takedown well milled - by .030 with a 3/8" end mill – 1st option – use a Dremel type tool to open up the pocket ; 2nd option - shave down the rear lug of the upper receiver to fit the authorized  pocket.

  • Buffer hole reamed - to 1 1/8"

  • Buffer hole tapped to -1 3/16" with 16 tpi

  • Rear takedown pin relief - cut with a 3/8" end mill & Grip hole tapped - with 1/4" by 28 tpi

Mounting the receiver within the BAXTER drilling fixture: The drilling fixture is a precision part.  It matches up with our forged 80% AR-15 lower receiver.  The jig is formed by two sides cross bolted together with the receiver in the middle.  The receiver indexes upon the jig on two sides.  The top surface of the BAXTER is matched with the top surface of the receiver and the rear surface of the jig matches the flat rear surface of the receiver.  Make these two surfaces flush and all your holes will be in the right place.

Basic steps for fixing the receiver within the BAXTER. TAKE YOUR TIME = do not hurry!!

  • Unbolt - using a 3/16 hex key wrench to withdraw the three cross bolts.

  • Remove top side.

  • Place receiver onto lower piece with the top of the receiver flush with the top of the fixture and the back of the receiver buffer tower flush with the back of the fixture.

  • Place top side of onto receiver and line up the three cross bolt holes.

  • Run cross bolts through both sides of the fixture and tighten evenly until it is snug.

  • Make fine position adjustments by using a straight edge to ensure the top and rear surfaces of the receiver are flush with the top and rear surfaces of the fixture.

  • Evenly tighten bolts until the receiver is firmly fixed in the fixture.

  • For best results keep the receiver in this fixture for the “COMPLETE” build, lock it in once and do every operation.

 

Drilling the front pivot pin with a 1/4" bit

The front pivot pin location is marked by the BAXTER drilling fixture.  Drill through both sides of the receiver in one operation.

Tools needed:

  • 1/4" drill bit

  • Drilling Fixture

  • Drill Press or 3/8" hand drill

Basic Steps:

  • Mount receiver in drilling fixture

  • Make sure receiver is mounted flush with the top and rear planes of the jig.

  • Clamp the jigged receiver to a flat work surface or drill press table etc.

  • Line the pilot pin hole in the drilling fixture directly under your 1/4" drill bit..

  • Make sure bit enters pilot hole as straight as you can.

  • Drill through both sides of the receive in one operation

 

Drilling the rear takedown pin with the 1/4" bit.

Drill through both sides in one operation.

 

Drilling the trigger pin with a 5/32" drill bit. Drill through both sides in one operation.  The fixture guides you in completing this hole.  Line the hole in the BAXTER fixture with your bit and drill.

 

Drilling the hammer pin with a 5/32" bit mounted in a drill press.

The receiver is mounted in the BAXTER drilling fixture and the entire work piece is clamped into a cross slide vise.  When using the fixture, drill through both sides of the receiver in one operation.

Drill the selector with a 3/8" drill bit.

The BAXTER drilling fixture provides a piloted hole for this operation.  Place the receiver into the drilling fixture.  Clamp the fixture to your work surface and drill through both sides of the receiver in one operation.  This is best accomplished with a drill press but can also be done with a hand drill.

Drilling the hole for the bolt stop plunger and spring.   

This hole is drilled with a 5/32 " bit (same as the fire control pin holes).  The BAXTER guides you in completing this feature.  Line the drilling fixture guide hole directly under your bit and begin drilling.  Drill this hole to a depth of .470".

Drilling the left side of the trigger guard with a 1/8" bit.

The Baxter provides a pilot for this hole.  Drill through both ears of the trigger guard in this operation.  This operation is performed on the rear trigger guard lugs or "ears".  Drill through both ears in one pass.  This operation is performed from the primary side of the jig.  After drilling, you will knock in a roll pin to secure the trigger guard.

Drilling the trigger guard detent with a 1/8" bit. 

This operation is performed using the BAXTER.  The secondary side of the jig features this pilot hole.  This hole is only drilled from the off side or right side of the receiver.  The hole only passes through one of the front trigger guard lugs.  Only the right side or "off side" lug is drilled out to provide for the spring loaded detent built into the trigger guard itself.  Drill through only one ear of the trigger guard in this operation.

Drilling the front pivot pin detent with the 3/32" x 6" aircraft bit.

 

Using the BAXTER makes it easy to clamp the work piece secure and square in the vice.  This hole is to be drilled 1 and 1/8" deep, and must be straight and true.  A drill press is the desired equipment for ensuring the hole is accurate.  Clamp the work piece under your drill head and position the bit in the proper location and proceed to drill.

The key here is that the detent be on center and perpendicular to the pivot pin so that the detent does not bind.  Use good manufacturing sense to ensure that your bit will not wander in this low tolerance area.

 

Drilling the rear takedown pin detent with a 3/32" bit.

This hole drills through to the takedown pin hole.  Position the drill bit directly over the correct location and drill through until you penetrate the rear takedown pin hole.  It should line up perpendicular to the center-line of the pin hole.  It is important to drill straight with this long skinny hole.  if you get crooked, the detent pin may hang on the takedown pin.

Drilling the selector detent with a 1'8' drill bit.

The selector detent is directly perpendicular to the center line of the selector.  It is drilled in two steps.  First, all the way through to the selector hole, and then counter sunk by 3/16" with a 5/32" bit.

Use the 3/32" x 6" aircraft bit to drill the pin hole for the bolt hold-open feature.

You should mark and center punch this hole location before mounting the receiver in the BAXTER drilling fixture.  The BAXTER provides a pathway for your bit when doing this operation, but does not pilot the bit directly like all the fire control and pivot holes.  The fixture does however allow you to conveniently clamp the receiver to your work surface. 

Give the location a good impression with your center punch.  Using a drill press makes this step very simple.  Just line the fixtured receiver under the chucked bit and bring it down to the center punched mark.  Lock everything in place and begin drilling, begin slowly and get a good bite, then drill through both sides to the lug in one operation.  Keep the bit lubricated and clear the chips often, withdraw the bit a little every-so often to aid in chip removal.  Chip clearing is very important when working with small bits as the channels of the bit can become clogged and cutting slows dramatically.

 


Close up, showing the bit contacting the lug, ready to be drilled

Stock Index drilled with 1/2" bit to a practical depth of .250"

Drilling the pistol grip hole using angle provision on the jig.

The BAXTER features an angled relief on one side to assist in clamping the work piece properly for doing the pistol grip hole and threads.  With receiver fixed into the BAXTER, clamp work piece in vise at an angle using the relief cut on one side as a guide.  Position work piece under drill head and drill with a 7/32" bit.  Drill through the receiver into the fire control well.

Drilling the buffer stop plunger with a 1/4" bit.

The BAXTER drilling fixture or "jig" features an angled cut on one side to guide drilling the buffer stop plunger at the correct angle.  Clamp fixture into vise using angle relief on jig.  Position clamped workpiece under the drill bit.  Bring drill bit straight down and drill to a depth of .712" per the plan.

 

Milling the fire control pocket by .030" using a 3/8" x 1-1/2" long end mill.

A cross-slide vise or compound table is required for machine completion of this procedure.  Additionally, the jig is required for strong and precise clamping of the work piece to the vise or table.  You should use a long end mill, that reaches all the way down to the bottom of the pocket.

Milling the fire control pockets with hand tools (OPTION)

The fire control well can be milled out with hand tools.  Use a rotary tool with a sanding drum and gradually take down each pocket side by .015".  Use a dial caliper regularly to check your progress.  When you get close, begin to test fit your fire control parts to the pocket as you near a perfect fit.  This procedure can result in a match grade hand fit.  The fire control well and rear takedown lug pocket can both be completed using this method.

Milling the rear takedown lug pocket with a 3/8" x 1-1/2" cut end mill. (OPTION)

Milling the rear lug pocket by .015 on each side using a 3/8" x 1-1/2" long end mill.  A cross-slide vise or compound table really helps in this step.  Chuck the 3/8 end mill bit in the drill press.  Position the front of the pocket under the mill bit, bring down drill head until it is just above the existing shelf.  Dial over the cross slide vise until the bit makes contact with the wall of the pocket.  Begin milling and slowly dial the table over by .015 +/- .002" to get the wall depth then dial the other axis of the table to run the length of the pocket all the way to the back wall.  Repeat this process on the opposite pocket wall and test fit your upper receiver.  The pocket must be evenly opened by .030" to a final width of .500" +/- .004".

 

Milling rear pocket with by hand with a rotary tool (option)

You can use a rotary tool to remove the small amount of material required.  Simply use a caliper to measure your progress and open the pocket by .015" on each side for a total widening of .030"  The end result pocket should be .500" wide and you are given + or - .004".  Take your time measure test fit the upper receiver often and this step is easy.


This blueprint detail shows the rear takedown lug pocket width as be .500" +/- .004

Boring the buffer tube from 1" to 1-1/8"

 Use a 1-1/8" Silver and Deming Reamer/Drill chucked into the drill press.  Run at 250-400 RPM.  Slower is safer.  Use a slow feed rate and keep the well  bit well cooled with fluid.

Tapping the buffer tube with the 1-3/16 x 16 TPI "Monster" Tap.

Fix the receiver in the BAXTER, turned on end and clamped square in your vise.  Line the buffer hole directly under the drill head.  Chuck a center punch in the press.  Place the tap straight onto the receiver and bring down the drill head to contact the back of the tap.  The shallow point of the center punch will index into the small hole on the center back of the tap for a perfect vertical alignment.  Apply light steady pressure to drill head and turn tap with a crescent wrench.

Tools needed for this procedure:

  • Drill press with vise
  • Jig
  • 1-3/16" tap
  • medium-large crescent wrench
  • 1/2" center punch or equivalent

Basic steps:

  • Fix receiver within jig.
  • Clamp jig in vise.
  • Chuck a live center or equivalent in drill press.
  • position work piece under drill head.
  • Use live center or equivalent to line up the drill head with the center of the buffer tub hole.  One way is to use 1" bit chucked into the drill head.  Position the work piece under the drill head so that the 1" bit perfectly plunges in and out of the existing buffer hole.
  • Clamp everything in place so that it doesn't move.
  • Remove 1" bit and put in 1-1/8" reamer or drill bit.
  • Drill hole to 1-1/8" all the way through.
  • Remove 1-1/8" bit and put in the 1/2" center punch.
  • Place tap onto the center of the 1/18" buffer hole.  Because the tap is slightly tapered at the end, you can set it in place and check for square as you bring the point of the chucked center punch to seat into the center hole on the back of the tap.
  • Check by eye that everything looks straight.
  • Provide constant down pressure on the press head to the back of the tap.
  • Turn tap with crescent wrench.  The first couple turns are the most important.  Check often to make sure the tap is staying straight and true.
  • Turn the tap 1/2 a turn then back it out 1/4 turn to clear chips.  Sometimes you can turn it more between back turning to clear chips.  Apply cutting oil before and during the entire procedure.
  • Tap all the way through the buffer tower.
  • After going all the way through, lift the center punch off the back of the tap and carefully back the tap out.

 

REAR TAKE DOWN RELIEFThis can be done with a Dremel or equal tool

  • Use a 3/8" end mill to relieve the right side of the rear takedown pin hole.
  • Use the jig to secure the receiver.  Clamp the jigged receiver within the vise.  Position the work piece under the chucked end mill.  Center the bit over the rear takedown hole.
  • Run mill bit @ 700 RPM and slowly lower bit onto work piece, cut to desired depth.  Cut should only be deep enough to remove small shoulder that would otherwise prevent the rear takedown pin from sitting flush against the receiver.
  • GRIP TAP Tap the threads for the grip with a 1/4" x 28 TPI tap.  This one cuts very easily, and is done by hand.  Start with a tapered tap and insert it into the pre-drilled hole from previous operations.  Use a standard tap wrench to turn the tap.  Thread all the way into the fire control cavity.

 

 

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