Some thoughts on gluing.
Gluing the plastic brick structure together is accomplished with ordinary super glue. You can use expensive super glue, or inexpensive super glue. Regardless, you will use quite a bit of super glue – have several tubes on hand – you do not want to run out halfway through gluing a part, knowing that by the time you get back from the hardware store, the glue you have already put down will be dry, and will keep the parts from fitting together properly. I would recommend the inexpensive type.
When gluing bricks down, putting a drop of superglue on the tops of the bumps of the brick below is not as helpful as putting some drops down where the brick brick connects to the surface of the brick below it; ie, if gluing a brick down, put the superglue on the surface of the brick below it, not on the top of the bumps.
The opposite is true for gluing plates or tiles (smooth plates) down. Put a drop of superglue on the top of every bump that will be under the plate. These drops will glue to the top of the plate.
Whenever possible, sand the sides of bricks that will be next to other bricks lightly, and blow off any dust you generate. Then as you glue the bricks, put a drop of superglue on the sides so the bricks will stick together, and not just be held by the glue on top & bottom. This is particularly important on the top structure of arches around the buffer tube.
Why is it so important to glue the sides of the arches together? Because after you superglue both structures together, you are going to pour .85 fluid ounces of mixed 2-part epoxy into the stock, and then shove a mil-spec buffer tube into the hole. The 2-part epoxy is liquid, and will seep out through any cracks you have left in the structure. So, when gluing the top portion of the stock, it is very important to put a thin line of super glue across every joint, preferably hidden between bricks. If you miss a spot, the epoxy will come squirting out there and you'll have to wipe it up quickly. You don't want to come in the next morning and find your nice new Feinstein stock epoxied to your work table.
Where else will the epoxy go? Through the hole in the back of the buffer tube. Not so good. Be SURE to put a few drops of superglue over the hole in the buffer tube, and let that dry overnight, before shoving the buffer tube down into the epoxy. If you forget this step, and now your buffer tube is half full of epoxy and your rifle won't cycle, we at Feinstein Gewehr Werke will happily sell you another stock kit – and a new buffer tube.
HammerHammer, of the Night Krewe at ARFCOM, happily came up with a fine workaround for seeping epoxy - electrical tape.
Before you shove the buffer tube into the stock filled w/ 2 part epoxy, slather a bit of the remaining epoxy on the bottom of the buffer tube where the regular stock lug goes into the holes on the bottom. Don't cover up all of the bottom with epoxy – the front part of the bottom rail will stick out of the stock. One of the pictures towards the end of the instructions shows where not to put epoxy.
We recommend you mix your 2 part epoxy in a small cup, then pour it into the well of the stock that you have built. Be ready to wipe up seeps after shoving in the buffer tube.
Take particular care in gluing the two parts together. DO NOT glue the 3 long center rods in place until you have glued together the top and bottom. The top of the 3 rods rest on the inside of the rearmost arch piece on the top. If you've glued your long rod a bit too deep, the top portion of the stock won't fit properly on the rear, and you'll have to do some cutting of your long rods.
Once you have the two parts glued together, putting in the rods is easy. Shove them in to check the fit, then pull them all out, and one by one, slather them in super glue and shove them in. Don't get your fingers stuck together! This is prime time for that. Keep track of which rod goes in which hole – don't get a long rod glued into a short hole. A short rod glued into a long hole will reduce the strength of your stock by an unknown amount – and your kid is likely going to have this stock next to his face while shooting his rifle or shotgun. Keep track of which rod goes in which hole before you glue them.
Tolerance stacking is a normal problem when playing with plastic bricks, and doubtless your kid has already experienced this and knows how to fix it. If a structure gets too out of whack b/c too many tiny angles have been introduced, a quick hard twist may fix it, or the structure gets taken apart and rebuilt more carefully, perhaps with more reinforcement.
Super glue prevents BOTH solutions. Super glue cures rather quickly, so be very careful as you put your bricks together with glue. If something isn't quite snapped down all the way, in 5 minutes your mistake will be preserved for a lifetime. This is why we recommend this stock be built 3 times – so by the 3rd time, you'll recognize any mistake you've made QUICKLY and have time to correct it. Once the super glue hardens, your only recourse is to replace those parts. If it happens late in the game, Feinstein Gewehr Werke will gladly sell you a new stock kit – but we don't do returns once bricks have been glued.
Tolerance stacking is a particular issue on the bottom of the stock, with the threaded rod channels. Get one hole off, and you're going to have a time getting those rods in place. The good news is, plastic does flex, and a stock that can stand up to 3” magnum shotgun recoil can use a bit of being banged on to force steel rods into place. TEST your rod fit BEFORE you glue them. You'll really be frustrated if the holes were a tight fit because of tolerance stacking, and then you banged the long rod into the short hole, already coated w/ super glue.
All is not lost in that case, however. You now have an excuse to go buy a Dremel, and FGW will send you a properly sized rod for the remaining hole – for a small fee, of course. (Less than the Dremel, anyway ; ).
Due to Effort Pelosi at the Feinstein Project, we finally realized what diameter of screws to use for our European friends - 5mm, of course.