Install AR/M16 Trapdoor Butt Plate

[cajungeo]

This is a great mod for your Hogue stock. The Hogue has a very nice finished compartment in the stock. There is a lot of room in there for lots of stuff. You may be able to do this with other stocks. Remove butt plate and see.

As you can see from the pic the M-16 Trapdoor butt plate is 3/4" longer than the Hogue stock. This issue can be resolved by modifying the Stock, butt plate, and trap door hinge.

Skill level needed: If you can bed a stock this is even easier to do.

Tools and parts needed: Dremel, assorted stones, sander, sandpaper, file, drill motor, 7/64 & 11/64 drill bits, countersink (crude one is a 5/16 drill bit)

As with all the mods here, they don't cost much. ;) I got a used M-16 trap door butt plate from Numerich Gunparts for $7.50. It was a little beat up, but I figured I could clean it up. I believe John Mason has new ones.

[cajungeo]

Mod to the M-16 butt plate:

1) Remove the trap door and hinge assy and set it aside and remove Hogue butt plate. Save the 2 screws for later.

2) Sand or file the inside flange off of the exterior part of the butt plate. Take your time, and try not to make it wavy. This is the line you will see between your stock and the butt plate. I used a disk sander, and file. You can also use a piece of 120 grit sandpaper laid flat on your workbench.

3) When you are finished with this task, the next step is to pot the holes.

4) Apply Mylar tape to the bottom side of the holes. The bottom hole will be completely filled, the upper hole will be potted, but the screw will have a new center more near the top of the hole.

5) Now for the tricky part: Use one of the Hogue butt plate mounting screws, apply a release agent to the screw. I used momma's cooking spray. Now install screw about halfway into the upper stock butt plate hole with the butt plate in place on the stock. Push butt plate downward so top of butt plate fits your Hogue stock every where except the 3/4" at the bottom.
Note: We are establishing the new hole center for the top hole only.

6) Using Accraglass Gel Kit and black dye or use JB weld. (You can paint your butt black later.) Pot the lower hole complete, and pot upper hole around the screw (the head of the screw should be up out of the way). Make sure the butt plate is fits on the topside, and sides of the butt plate and stock. Only the lower part should be sticking out.

7) Now prop up undisturbed over night allowing potting to cure. Be careful because nothing is holding the butt plate on. It's just sitting there. I put mine in a vice with the butt sticking up.

[cajungeo]

1) To mod the door hinge half drive out the hinge pin with a punch.

2) Cut hinge half to match the pic. Don't cut too much. I left a little bit of the old hole.

3) Round up corners

[cajungeo]

After butt plate potting is cured, mark outer periphery of plate to be worked down to shape of stock. Should be the area at the bottom of the stock. See photo how mine fit.

Yes we will be cutting into the potting where the old hole was. Don't worry I won't make you mess up. ;)

[cajungeo]

Modify the Stock

When you've finished with fitting the plate to your stock the next thing is to mod your stock to accept the hinge, and to drill a new lower hole. This mod will still allow you to remove the Trap Door butt plate, and reinstall the Hogue butt plate anytime you like.

1) Reassemble hinge half, and door to the butt plate. We will use this to measure the fit as we are working down the stock's Lower mounting lug. Don't mess with the upper one its fine as is.

2) Lock your stock in a vice (Only snug with jaws taped). Dremel the lower lug about 1/4" deep and all the way to the inner wall of the stock. See photo.

[cajungeo]

After you have your butt plate fitted so the hinge sets inside the stock, our next task is to drill the lower hole.

1) Lay your assembled butt plate hinge down on a board or work bench.

2) Now be careful with this part: The hinge half is much shorter than it was so center a 7/64 drill side-side and between hinge notch, and edge of plate. This hole must be drilled at about a 5-10 degree angle inward. You can drop down and see how this is going to be.

3) Drill thru plate, and stop as bit touches hinge half. This is your last chance to realign things, then proceed to drill thru steel hinge half.

Note: Don't worry about the edge margin. Mine was very thin, but it is steel and strong enough to hold.

[cajungeo]

1) Next place butt plate assembly onto stock by installing the upper screw.

2) Insert the 7/64" bit thru the new lower hole in plate assy, and drill into the stocks modded lug.

3) Remove butt plate assy, and open both holes with a 11/64" bit [B](Butt plate, and hinge half only! Not the stock!)

4) Countersink holes so heads are flush with surface.

[cajungeo]

Ok now you can sand it, polish it, or paint it. Just make it as purty as you like it.

I was in a hurry with mine. You can see the potting, and where I sanded. I will purty it up when I get more time.

Job well done, it looks cool, and is functional. Now what all are we going to put in there? :unsure: