Join Date: Oct 2014
Location: Red Lake Falls, MN
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Under Trunk Lid Mount Law Enforcement Style Weapons Rack
Tools and Parts List at end of instructions closely matching my entire set up. You can vary depending on your choices for set up. There are two types of 1/8” aluminum plates that you can get. One is a mirror smooth plate. Second is not as smooth and very matte looking. I’ve used both types before on different projects. For this project is used the first one that is mirror smooth.
Need 1/8” aluminum plate to mount to underside of trunk lid. As long as the mounting plate and all accessories are kept within the area covered by the trunk lid liner, the trunk seals will be cleared for closing the trunk. There are four plastic rivets that hold the trunk lid liner into two support channels that will be used to mount the aluminum plate.
First photo will show the entire underside of the trunk lid with liner.
Second photo will show the left two plastic rivets that will be removed to mount plate.
Third Photo will show the right two plastic rivets that will be removed to mount the plate.
Depending on skills and tools available, measure out mounting plate and cut it to size and shape rounding the corners and removing all sharp edges. Then tape together paper or card stock (better to work with) and place the mounting plate on the paper and trace it out to create a template. This is the method I used.
The other choice is to create the template. Bring the template to the machine shop and have them cut the aluminum plate out to size and shape for you. If necessary, you can even include all of the bolt hole locations on the template and have them drill the holes for you.
Measuring Mounting Plate
The mounting plate needs to extend past the four holes by at least two inches in all directions. The larger you go with the plate, the more accessories you can add to the plate. The dimensions for my mounting plate are about 36” wide across the top, about 42”wide across the bottom, and 12” tall.
Fit Template to Car Trunk Lid
Remove all the plastic rivets with a panel removal tool and set rivets and trunk lid liner to the side. Liner and most rivets will be reused. Fit template to underside of trunk lid and tape into place. Make sure all of it is inside the area covered by the liner and covers all four target holes evenly. Make sure it is centered and even over the holes. Use the edge of a screwdriver handle or large socket to mark the four target holes into the template.
Create Template Bolt Hole Locations
Take Template down and lay it on the table. Two holes are marked on each side of the template. Use a pencil to mark center of the four holes. Between the two holes on the left side evenly space two more holes in between them keeping them centered so they stay on the raised channel on that side. Repeat for the right side. The four bolts that go on each side can be seen in the fourth photo.
For the plate size I used, I had to mount the rack so the rifle dropped out the bottom of the rack. There was not enough clearance to lift the rifle of the rack if I would have mounted it top load. The 90 degree bend of the trunk lid prevented that without the plate coming down much lower to mount it lower. It really doesn’t matter since the strap and lock holds the rifle in the rack solid. Besides, since the lid is closed most of the time the rifle lays on its side and the strap and lock keeps the rifle from moving forwards and backwards.
Mark Gun Rack Bolt Holes on Template
The gun rack I chose is a Big Sky Racks ELS 275 #1 electronic lock with key override meant to mount an AR-15 with collapsible stock in an optics protected position covering the takedown pins. I placed the firearm in the rack and test fitted it on the template with both the shortest barrel model and longest barrel model I plan to mount. That way I can be sure nothing extends past the trunk lid liner so everything clears the trunk seals.
I found out that I could mount rack completely centered top to bottom and left to right. That places a 10” SBR centered and leaves room for up to an 18” barrel model to be mounted. I disassembled the gun rack sketching on scratch paper what bolts up to which hole on the rack. Then I placed the stripped rack on the template and centered it in all directions. Then I marked all bolt holes out on the template.
Mark Blackhawk Serpa Quick Disconnect Bolt Holes on Template
As can be seen in the fourth photo above that I placed three Blackhawk Quick Disconnects on the template. The fifth photo shows that I assembled the pistol holster to a quick disconnect, a dual rail to a quick disconnect, and a molle attachment and molle AR-15 mag pouches to a quick disconnect.
I then test fitted them all to the template to make sure they all fit and did not interfere with the gun rack, mounted rifle or bolts. I marked the outside of the quick disconnects. I separated the accessories from the quick disconnects, placed the quick disconnect back on the template and marked the mounting holes.
Mark Bolt Holes on Mounting Plate
Tape the template to the 1/8” aluminum mounting plate. Use a center punch and hammer to mark center of all bolt holes onto the mounting plate. Just place center punch on center of hole marked on the template and punch right through the template and into the marking plate. After all bolt holes are marked, carefully remove the template.
Mark Mounting Holes on Trunk Lid
Cut out the original plastic rivet holes on the template and use four plastic rivets to hold the template to the underside of the trunk lid. Using center punch and hammer mark the four new mounting holes into the underside of the trunk lid. Remove the plastic rivets with the panel removal tool. Remove the template and place aside incase needed for reference in drilling holes in the trunk and mounting plate.
Install Nut Inserts into Trunk Lid
Install eight 5/16”-18tpi Nut Inserts (Blind Threaded Studs) into underside of trunk lid. Drill the eight holes for the nut inserts. Step up in size in drill bits up to the final size needed using drill stops to be sure not to punch through the top of the trunk lid. Depending on nut insert used the final drill bit will be 1/2”. Make sure nut insert used is correct for the thickness of material and strong enough to hold the weight. Install the nut inserts with the nut insert installation tool.
Drill Holes into Mounting Plate
Drill the eight 5/16” mounting holes into the 1/8” aluminum mounting plate. Start with a smaller bit size and work your way up. Once all eight holes are drilled, test fit the mounting plate to the trunk lid and make sure all holes line up. If one doesn’t quite line up, oversize the hole a little until all bolts will start.
Drill all the holes for the gun rack to install 5/16th-18tpi nut inserts.
Drill 1/4” holes for all the Blackhawk Serpa Quick Disconnects.
If you would like the mounting plate painted, now would be the time to do so. Make sure all paint is dry and cured enough before continuing anymore work on mounting plate. If you need to, you can skip ahead to electrical work and come back again when the paint is dry.
Mount Everything to Mounting Plate
Install 5/16”-18tpi nut inserts into all bolt holes for gun rack. Mount gun rack to mounting plate with 5/16”-18tpi x 3/4” bolts. Mount everything back into place on gun rack as noted earlier. Mount electric lock ground wire under one of the bolts. If you want this to be a secure mount, use button head allen head bolts. After everything is fitted and function verified, use proper side drill bit and round out allen head bolts. It creates tamper resistant bolts. Test fit rifle into gun rack to make sure everything fits before tightening everything down.
Mount Blackhawk Quick Disconnects to mounting plate with the hardware included. A hammer will have to be used to tap the nuts into the mounting plate. Make sure to use the longer screws and nuts.
Drill hole through mounting plate for trigger wire for electronic lock. Protect the wire with shrink tubing or electrical tape. Add a wire connector to the wire for connecting the gun lock to wire harness for easy connection and removal.
Installing the Electrical Components
There are a couple of electrical components that will need to be mounted. First, is a push button switch to release the weapons lock. Second, is a weapon release timer that releases the weapons lock for ten seconds.
Push Button Switch
Find a location that you would like to place the push button switch. Someplace out of sight or hidden that you can still easily reach would work. That will help add to the security level of the electric lock system and protect the switch from items in your trunk.
If desired, a programmable key pad can be substituted to increase security without tapping into switched electrical wiring. That way a code would have to be punched in to release the lock. The keypad could be mounted right on the mounting plate for easy access.
Weapon Release Timer
If you pull the carpet liner inside the trunk for the right rear quarter panel, you will find a nice recessed area that easily fits the timer. That way the timer doesn’t come into contact with the liner or other material since it can get warm with repeated use. It also places the timer close to the fuse box and battery.
Wiring schematics for the car and experience tapping into automotive wiring helps. Knowledge of how tap into the existing fuse box would be very helpful. There are plenty of resources and videos that can teach how to tap into existing fuse boxes and other wiring tips and tricks. Wire tappers and soldering skills can also come in handy. Whenever possible I ran wires alongside existing wire harnesses and taped them up with the new wires after all wiring is completed. Make sure to leave enough slack in the wires to put everything in place.
First wire needed to run is from a source that is only hot when the ignition switch is on. Since I have keyless entry I found a function that is only hot when my key fob is near the trunk. I tapped into that source and ran a wire to the one side of the push button switch and connected it.
Second wire needs to connect to the other side of the push button switch and run down to the weapon release timer. Wire connectors can be used but I recommend soldering this wire to the yellow trigger wire on the timer. Use heat-shrink to cover and protect the connection.
Third wire needs to connect the black wire on the timer to ground.
Fourth wire needs to connect the red wire on the timer to a 15 amp fused power supply that is always hot. First choice can tap into an always hot section of the fuse box not being used and use a 15 amp fuse. Second choice can use a 15 amp fused link and connect to the positive terminal of the battery.
Fifth wire needs to connect to the green wire of the timer and lead up to the center of trunk where the gun rack will go and can be left a little long for now.
The weapon release timer can be attached to the recesses area of the quarter panel with double sided tape or Velcro. All wires can be taped to wiring harnesses and hid behind carpet liners. The right quarter panel liner can be put back into place.
Modify Trunk Lid Liner
Trunk lid liner can be laid out flat. Place the mounting plate on the liner centering the four rivet holes inside the outside four mounting holes. Mark the inside four mounting plate holes on the liner. Drill or cut the eight holes on the liner for the mounting bolts to go through. Test fit the liner to the mounting plate to make sure all eight holes line up and clear the bolts through. Cut an X in the trunk liner close to where the trigger wire comes through the mounting plate.
Mount Everything in Place
Trunk liner can be attached to underside of the trunk lid with the plastic rivets in the remaining rivet holes. Make sure to pass the trigger wire coming from the timer through the X cut in the liner. Trigger wire can be trimmed to a length easy to work with and electrical connector added to mate to the trigger wire coming through the mounting plate. The reason the trunk liner is put back in is to use it as a vibration damper to quiet any metal on metal noise. It also covers all the wires and trunk latch components giving it a finished look.
Two people will almost be essential to mount the mounting plate to the trunk lid. Get al mounting bolts and tools handy and laid in trunk for easy access. Connect the trigger wires and line up the mounting holes. Get four bolts in at least finger tight. Get the other four bolts in. Tighten all eight bolts evenly. Works best to tighten them a little at a time to snug things into place.
Test Electric Lock
Make sure lock is closed on the gun rack. Since mine is wired into components requiring key fob I place key fob out of reach of car and test the lock pushing lock button. It shouldn’t work. I get the key fob and try pushing lock button. It should release. It is designed to stay shut incase weapon is removed so you have to pull the lock open by hand to see if it works. You have ten seconds to do so. If there is pressure on the lock, you might have to give it a slight push closed before pulling open to release.
Test fit rifle into gun rack to make sure everything fits and lock functions. Make adjustments as necessary. Any other accessories can be added to the mounting plate at this time. Be careful during this process not to apply pressure down on trunk lid. Also be careful that trunk lid doesn’t fall while working on it.
Stiffer trunk struts should be added to assist with the extra weight. I will update the thread when I get my stiffer struts and how they work.
In the fifth photo shows the final project completed. Depending on the strength of the new trunk struts I might add a couple more things. I will also be adding LED lighting so the gun rack can be seen at night Current trunk light doesn’t help at all.
Panel Removal Tool
Assorted Drill Bits
Assorted Drill Bit Stops
Assorted Hand Tools
Nut Insert Installation Tool
Assorted Electrical Wiring Tools
5/16”-18tpi x 3/4” long Hex or Button Bolt – 20 each approximately
5/16”-18tpi Nut Insert (Blind Threaded Stud) – 20 each approximately
1/8” Thick Aluminum Plate 42” wide by 12” high (Could vary upon your design)
Big Sky Racks ELS 275 #1 Law Enforcement Electronic Locking Rack (Ordered straight form Big Sky Racks)
FF Flat Surface Mount Option
(B) Standard Key Override Option– Can choose (A) Handcuff Key or (R) Barrel Key Override
Can also choose opposite facing style than photo like I did option
Hook and Loop Fastener kit or Double Sided tape
Assorted Electrical Connectors and Wire for electric lock components – Depending on choice connecting
Heat Shrink Tubing
Optional Parts List
Blackhawk Serpa Quick Disconnect Kit – 2 each
Blackhawk Serpa Quick Disconnect Male – 1 each
Blackhawk Serpa Holster to match your pistol
Blackhawk CQC Dual Rail Accessory Belt Loop
Blackhawk CQC Spacer Kit (to provide clearance to fit Dual Rail to Quick Disconnect male connector)
Blackhawk Mag Case
Blackhawk Flashlight Case
Molle Attachment Kit
Molle AR-15 Mag Pouches