Its a complex subject. We start with not having a clue what the base polymer is.
There are commodity resins which may be relatively cheap. Polyethylene,polypropylene,ABS,PVC come to mind.
You can take a polyethylene or polypropylene bowl and mix epoxy in it,pour out most of it (so heat doesn't build up) come back the next day,flex he bowl,and the epoxy will crack off . You can use the bowl again. Pretty much,nothing sticks.
ABS and PVC can be solvent bonded.Styrene is another.Solvent melts the plastic. It sort of welds together. Plumbing and model airplanes.I don't know of gun applications.
Delrin/acetal...Might give you the illusion epoxy/superglue sort of sticks.It will fail.
Acrylic/plexiglass solvent bonds.And there are 2 part catalyzed specalty glues that work pretty well. But guns don't have plexiglas stocks
Polycarbonate! Tough stuff!! Long carbon chain molecules.Amazng,at normal
tapping speeds,even hand tapping,those carbon chains get broken,and release heat.The threads will easily melt. Look very close,you will see suspended black flecks of free carbon. Polycarb can take impact an shock. It does not like sustained stress. Polycarb can be solvent bonded. Solvent polished,too.But as the solvent evaporates,it leaves a stressed layer.
Ever get a glass marble hot and throw it in cold water? It will crackle and craze.Polycarbonate is susceptible to solvent stressing and crazing.
There are urethanes and other exotics... I've been out of it for 20 years. New stuff.
Many polymers are filled with something else. Glass,graphite,talc.corn starch,etc. You might get glue to stick to the filler.
With a porous material like wood,glue can penetrate and mingle with the wood fibers. You might tear wood out before the glue lets go.
Not so much with polymers.
I'm not a chemist,its been over 20 years,but polymer molecules look like spaghetti noodles. There are different ways the molecules bond. I forget which is which,but there are Brownian,Covalent,and Vanderwahls bonds.
Someplace in all of that science will be your adhesion answers.
I don't know what a Choate or a Ram-line stock is made like,but I'll describe a process of co-injection that a stock COULD be made of.The way plastic flows through a mold,it sort of rolls within itself. Ther is little,if any friction between the mold and the skin of the polymer. By friction,I mean movement.The polymer skin gives up its heat to the mold and solidifies. The mold continues to fill within this shell.
With some molding machines,its possible to begin filling the mold wth one resin which will form the skin,then switch to another resin that will form the core. So your part ends up like chocolate covered cherry. Now,you can think a little bit like case hardening. You can have a relatively expensive outer skin of engineering resin,with a cheaper core fill.
Now,here is where it gets fun!!
Maybe nylon 6/6 will get a graphite /fibergass fill.That enhances the characteristics of the nylon. There is more. Polymers shrink when they solidify. Nylon? Ballpark .007 to .009 per in. Polyethylene/polypropylene? You might get .020 or .022 per inch. That causes problems with snks,warps,etc. Internal stresses. But now,when we add fill,the fill is not subject to shrink . So,if your nylon has 40% fill,you might cut your shrink to .004 per in. There is another trick! A blowing agent,like baking soda an be a polymer additive.It makes the polymer foam.
So you could shoot a part with a hard skin of Graphite glass nylon 66 with a foamed core of polypropylene.
I'm not saying thats what they do,but you would have an accurately molded,servicable relatively cheap stock. And glue,epoxy,etc would not stick worth a darn.
That stock is a whole different ballgame from a composite stock,such as a McMillan,which is laid up of epoxy glass,kevlar,graphite with a foam core.
You can get epoxy to stick to epoxy
Note to Unclenick I'm not an epoxy expert,but there is something about a volatile solvent in the catalyst..like maybe acetone or methylene chloride.
Its a problem if it evaporates too fast. So the magic is,some kind of wax floats up and forms a protective skin over the curing resin.
Thats why the timing thing on recoat.
You can get good adhesion on a recoat after the time,but you need to sand or otherwise remove the wax film.
Now,a little knowledge is a dangerous thing,and thats what I have. I'm sure my explaination is at least partly wrong, but certainly I will be corrected!
