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Gunsmithing HOW-TO: Put Flush Cups in Hollow Tupperware Stocks

Hellbender

Gunny Sergeant
Full Member
Minuteman
Apr 23, 2008
1,560
314
Lebanon, Missouri
Here's what I did to a hollow A1 style stock, but this will work on any type of hollow, thin plastic/nylon stock...

Take a piece of sheet metal and cut it to fit inside the stock. I used an old cover plate off an electrical box, as it was about the right thickness. This plate had to be cut a little oddly to fit the weird surface I had to work with inside the A1 stock. A 1/2" fender washer would also work well.
Put a very slight bend in the plate to fit the curvature of the stock inside...
DSC00079.jpg


Drill a hole in it to fit the Flush cup and JB Weld it to the metal plate. Always make sure the cup is slightly ABOVE the surface of the stock when done.
DSC00078.jpg


Drill a hole in the stock and glue it inside. Make sure you clean/degrease the metal plate well and rough up the inside of the stock and degrease.
As the plastic stock may flex slightly, use a strong flexible adhesive (I use Shoe-Goo) to adhere the plate to the stock, don't use a hard epoxy.
This A1 stock does not have the foam inside and is just a shell..
DSC00080.jpg
 
Re: HOW-TO: Put Flush Cups in Hollow Tupperware Stocks

Thanks for the info. I saw your build thread in the other forum. I'm gonna have to do this on my A1 stock. Please post some pics after the cerecote. The rough finish the stock has always annoyed me. How does that stuff hold up on plastic?
 
Re: HOW-TO: Put Flush Cups in Hollow Tupperware Stocks

I don't know how it does on plastic, I am just planning on doing the metal parts.

Do you have one of the new, Cavalry Arms stocks (Like mine above) or an older "real" A1 stock? The Cav Arms stocks do not have any of the foam stiffener inside, just a hollow shell.

My old SP1 Colt stock is much nicer, but they are very hard to find in good shape, most of the used ones for sale are separating inside (the foam and shell).

I'd try the Krylon "Fusion" paint for plastic, or the Air Dry CeraKote may be good. Sand the stock first to get it slick.
 
Re: HOW-TO: Put Flush Cups in Hollow Tupperware Stocks

I have the hollow Cav Arms stock. I probably won't get around to painting it, but I'm gonna have to try this flush cup thing. I might buy another stock just to experiment on.
 
Re: HOW-TO: Put Flush Cups in Hollow Tupperware Stocks

I did something similar with mine. I just filled the inside/bottom of the stock up with JB Weld until it covered the flush cup. Works great and has that M-110ish look to it.

DSCN0062.jpg
 
Re: HOW-TO: Put Flush Cups in Hollow Tupperware Stocks

When I replaced the Nato stock with a "Warsaw Pact" length one on my Arsenal A1R AK in 7.62X39, I added a lefty sling setup.
I was able to bolt the flush cup down to the other side, after making the proper length nylon spacer, and cover my handiwork with the standard sling swivel.
The front was even easier, with the steel heatshield serving as an attachment point.
I've had good luck with JB Kwik. I know it's not as strong as the regular stuff, but it seems more than strong enough. And it's fast.
 
Re: HOW-TO: Put Flush Cups in Hollow Tupperware Stocks

Any ideas on how to install flush cups on a Rem 5R stock?
 
Re: HOW-TO: Put Flush Cups in Hollow Tupperware Stocks

fe1...

Look up any of the older threads on installing flush cups on any high end stock, there are a bunch.

You just drill a hole the proper size and epoxy in the cup.

Edit: I guess the stock shell on those 5R stocks is pretty thin and may not support the cup properly, I think I've got a PSS stock around I'll try and look at it and see if I can figure something out.
 
Re: HOW-TO: Put Flush Cups in Hollow Tupperware Stocks

I used a flat 9/16 x 18 nut on the inside of my A2 stock to good effect for a side-mounted cup. I originally drilled the stock to 17/32 and threaded the cup in but just didn't think that there was enough material there to give the threads adequate purchase. I enlarged the hole to 9/16 which was still tight enough for a light press fit for the Grov Tec cup. I fiddled around with the thickness of the assembly and ended up at .60" which left me with about 4 threads worth of engagement on the nut. I JB Welded the cup/nut assembly together and coated the mating surface of the nut and 1/2 of the protruding cup with adhesive as well. The inside of the stock was roughed up with coarse paper. I had hoped that there would be enough excess adhesive to fill in the slight void between the head of the cup and the stock but the relatively tight fit wiped the excess away when the assembly was inserted into the stock. I'll go back and hit that with some black silicone caulk.