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Bedding thermoplastic
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Greetings all,

OK, this was spawned by another thread -- I had intended to bring this out at some point anyway.

What can you use for filling in the gaps / bedding on a thermoplastic stock? Any kind of surface prep that helps adherence?

Question two: once bedded, what kind of finish is recommended (I was thinking something like the spray on bedliner I heard mentioned).

Thanks,
Todd

[This message has been edited by Todd Getzen (edited 07-27-2001).]

 
Posts: 1248 | Location: North Carolina | Registered: 14 April 2001Reply With Quote
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Most of your expoxies don't adhere well to the plastic stock materials. I've done three things to insure the bedding/filler stays in. First is to rough up the clean surface with a rasp or rotary tool. Second, degrease with either acetone or brake cleaner. Three, drill bosses where the material is to be placed to enable mechanical retention. In the recoil lug area I've drilled a couple of 45 degree holes through the boss which I later filled the epoxy for a mechanical grip. Haven't had a one out of maybe 20 or so I've done, come loose yet.

Where I have occasionally made a blunder and drilled through a stock while trying to drill holes at an angle, I've use repair tools used for the repair of the plastic surface on snow skis. I suppose a soldering iron with a broad tip might work as well. Repair with a ski surface welder is unnoticeable.

I also use Marine Tex as the filler which seems to hold a bit better than AcraGlas or Devcon.

 
Posts: 1261 | Location: Placerville, CA, US of A | Registered: 07 January 2001Reply With Quote
<Don G>
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Todd,

Someone here suggested using the commercial cleaner and primer solutions designed for ABS plastic pipe. (I think some is marked for PVC and some PVC/ABS - you want the latter.) It has acetone and MEK in it, I believe.

I used acetone and the mechanical interlock technique Bob talked about. Think dovetail and you've got the idea. I used a 5/32 burr to cut the dovetails. I've only done two stocks, a 308Win and 300WinMag, but they both held up.

I think bedding those stocks is polishing a turd. It may work a little better, but it is still a turd! They just seem to squirm in my hand - especially on a warm day.

Don

 
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I would go along with what Bob338 does. I also sand them with very course sandpaper.

As to the stocks themselves, I have found the accurayc that csan be obtained (at least on larger calibers) is superior to other stock material. Most of my experience has been with the Rem 700 stocks.

A few years ago I did some extensive testin of the 358 STA. 3 barrels were tried, all .72" at the muzzle, .357 groove diamter and 1 in 14 twist, Rem 700 Stainless action with Jewell trigger at 2 pounces.

As an extra experiment, a barreled action was bedded into the Remington factory stock, a walnut stock that was off a 416 Rem 700, a fiberglass stock and an aluminium stock we use as becnh stocks out here.

Best accuracy came from the Remington injection moulded stock. By the way, the walnut stock was next, aluminiun next and the fiber glass last.

I have not done enough testing to be sure but I think the one of the Model 70 will produce a similar outcome.

Mike

 
Posts: 7206 | Location: Sydney, Australia | Registered: 22 May 2002Reply With Quote
<Jordan>
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For what it is worth, I concur with Bob and Mike. I have bedded one plastic stock. I found that a rotary sanding drum in a dremel tool worked real well for roughing the surface. Basically, the sander melts the plastic and leaves the surface quite rough. Any undercutting or drilling you can to to create "negative voids" for the bedding compound to flow into will also help because I think the bond is essentially only mechanical.

Jordan

 
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