stock filler for a glass fiber re-enforced poly stock?

[scythefwd]

Yeah, I know, awkward way of saying it, but thats what owners are saying it is...

I'm probably going to be looking to fill in the forearm a bit so I can inlet and add an anschutz rail to the stock. Its definitely polymer.. as to what type.. thats more up for guess. Rifle is a bergara b14 hunter.

Any suggestions on a two part epoxy that will stick to either nylon or plastic? Looking at jbweld steel putty or devcon 10110 or marinetex at the moment, but I dont know if they'll stick. Yes, common practices such as drilling off angle holes and roughing up the surface with sandpaper (or adding scallops with dremel) would be done just to make sure. Not bedding the rifle with it, just re-enforcing the forearm to remove flex and give me enough backing to put the rail in ...

 

[edwardware]

If my experience with Remington's tupperware stock is any indication, then it's polyethylene and nothing will bond very well. In that case, you'll need to create mechanical interaction, because chemical bonding is almost impossible in PE.

I opted to buy a Boyds stock for ~$120, and it's great!

 

[Kp321]

I use the lowest viscosity epoxy I have, original Acraglas, and rough up the interior of the plastic. I use an aggressive cut carbide burr run fast to actually melt into the plastic and leave an ugly groove with whiskers sticking out from the surface. Plenty of surface area for the thin epoxy to bond to.

 

[scythefwd]

KP. .thats kind of where my mind is going.. Setup mechanical locks.. possibly cut out the ribs in the stock and hand lay some fiberglass that is mechanically locked into the stock there (groove the sides, or pock mark it with a dremel, etc..

I may have to mix up some of my jbweld and see if it will stick inside.. Pick up the rifle tomorrow, so it'll be a week before I can comment for sure.. test it after some shooting, etc

 

[Sunray]

Synthetic stocks require a bit of roughly up for anything to stick. Sandpaper is plenty.
I'd be inclined to talk to Bergara first though. Their rifles are pillar bedded and filling the forestock will alter the balance. They might have a ready made solution to mounting a rail on a hunting rifle. There are rails use the scope base holes too. Not exactly inexpensive though.
http://www.badgerordnance.com/scope-bases.html
http://www.bergarausa.com/contact.php

 

[scythefwd]

Sunray, I believe you misundstand the intent. Those are weaver or picatinny rails.. not an anschutz rail. An anschutz rail is ALWAYS embedded, flush mount, to the bottom of the forearm for accessories like hand stops, wieghts, rifle rests (not bipods, but they look it), etc.

like this

that one is being glued into the stock.

Of course it will effect the balance.. but that can be corrected with a ballast weight in the stock. im talking about adding ounces, not lbs here.

I did contact bergara, and to quote:
The stock isn’t a fiberglass or wood stock like what those rails typically go on. I wouldn’t recommend an Anschutz rail being installed on the HMR stock. I'm checking with the technical manager to see what he would recommend for a handstop.

but that was expected. i may have to see if i can get fiberglass to stick in there and mould things in that way...

 

[LoonWulf]

I would probably inlet it and attach with machine screws thru the rail and stock, to nuts or tension plates on the far side, if theres enough material. You could then use a epoxy like west system 105 or gflex to fill any gaps and create that "fitted" look (unless of course your inletting is really good in which case the mechanical connection should be enough.

If there ISNT enough material id probably fill the voids in the stock where the rail will go with slow cure epoxy, or thin layers of fast (to get as little shrinkage as possible). Build it up till theres enough material to use a mechanical attachment and again go with machine screws and fasteners.
That process should if nothing else leave you with some chemical adhesion as well as a mechanical lock between your filler, the stock, and your rail.

Ive also have decent luck gluing to poly if you first flame the work piece, on a stock im not sure how that would work but it might be worth the try.
heres a guide that i just pulled up.
https://www.jamestowndistributors.com/userportal/document.do?docId=420
I had to practice a few times to keep from burning the plastic, but thats basically what i do.

 

[scythefwd]

Loon, second option is what I'm looking at.. and creating a mechanical lock between the filler material and the stock by putting grooves in the stock on the inside..

 

[LoonWulf]

Loon, second option is what I'm looking at.. and creating a mechanical lock between the filler material and the stock by putting grooves in the stock on the inside..

That sounds like it will probably be the best option. Im looking forward to seeing how it comes out!

 

[scythefwd]

Well, delayed. Manual said tq to 7Nm (61.955 in lbs), and that crushed the integral pillars, new stock is in route.

 

[LoonWulf]

How interesting! The synthetic has the same epoxy pillars as the wood stocks? I havent looked.

 

[scythefwd]

It appears so. it also appears they're not capable of handling roughly 60-62.5 in lbs of torque without going to pieces. that said, at least in the polymer stock, the addition of steel or aluminum pillars would be trivial and inexpensive (less than a dollar or two per stock I suspect, especially since they could make hundreds per hour with the machinery they currently have). Instead of putting the polys in place and moulding the stock around it, drop aluminum ones in place. Something that couldn't be done in the timber, but since they're already doing a pillar job on the timbers, it would be no extra work to use a better, less compressible material. And I suspect that will be my first upgrade to this rifle.. that or a bolt knob.

 

[Bwana John]

If it is polyethylene why not use a hot air plastic welder to beef it up before carving out the channel?

That is the only thing that will fuse the material, every thing else will rely on mechanical jointery.

 

[scythefwd]

I think I'm going to have to work with mechanical joint no matter what.. its pretty difficult to use a plastic welding rig when you literally have to build up 1/4 inch. I'll have to check and see what actually bonds to the stock and how well. I'd really prefer NOT to strip all the support members out to bond something in if at all possible. That said, I may attempt to create a mechanical lock on a piece of fiberglass formed to the stock bottom, and then build up that way with fiberglass.. use some sort of fiberglass mat as the bottom layer, heat the mat with soldering gun or the like to embed it into the stock a little bit, then use my resin to wet it and build it up as need be.. Who knows, appreciate the idea though. There is some stuff called pro-poly from innerduct that is a hdpe glue that will also bond to fiberglass, so there is a possibility there