The following write-up will look at changing the ERTL Rapid Fire Shotgun (RFSG) original kid-sized brown shoulder stock to a more practical M4 shoulder stock.
For those who are keen to know more about Doomsayers (modded RFSG), you can read the original mod guide by Forsaken_angel24 at the NerfHaven forum:
Note that there are many methods to do shoulder stock mods on blasters, this isn't the only (or best) way, its just something i tested and worked.
Get your choice of replacement shoulder stock. In my case, i got a plastic replica adjustable M4 shoulder stock.
Use a dremel or handsaw to cut away the back portion of the RFSG, in my example i cut it at the section with the largest opening.
Ignore the 2 black pieces of plastic in the photo, its just some spare bits from part of the cut out section that i figured could be useful to cover gaps. Didn't get to use them eventually.
Measure and nest a length of 13mm SingaPlastics PVC pipe inside a shorter length of 16mm PVC pipe, this will become the connection point.
Open up the replacement shoulder stock and position a 13mm PVC end-cap inside, you'll have to trim and sand down the shoulder stock internals until it fits.
Bolt on the connection point pipes to the RFSG shell, i used 2 countersunk machine screws to secure it to the shell. Note that the shell is in 2 layers, so i bolted it to the inner layer.
Drill and sand out the replacement shoulder stock until it has a rounded opening to accept the connection point pipes, then glue the 13mm PVC end-cap permanently inside the replacement shoulder stock. I also added a ring of foam padding to help cover the gaps between the shoulder stock and casing.
Photo: (Left) Original replacement shoulder stock / (Right) Modded replacement shoulder stock.
Assemble everything back together and connect the new shoulder stock, its complete!
The plastic replica M4 shoulder stock i used is adjustable so it could be extended to different positions. Much more comfortable and steadier when shoulder aiming.
One of the main reasons why i did this mod was also because the Doomsayer was originally too long and it could not fit into any of my carrying cases or bags! I was getting sick of carrying it around in plastic bags with all the barrels sticking out! :)
With the shoulder stock being removable, it can now fit nicely into a large padded case.