Bondo as a bedding material

[mickri]

Just about done with the inletting on my second stock from Richards Microfit. Still working on the barrel channel. Next task will be to bed the actions in the stocks. I typically use epoxy thickened with cabosil or wood sanding dust. I have read about people using all kinds of stuff for a bedding compound. JB Weld is real popular over on the accurate reloading gunsmithing forum But have never read about anybody using bondo. One benefit of bondo is it dries so fast. 15 to 20 minutes max. Another would be it's not a glue. It is a filler. Less tendency to glue the action to the stock.

I have the old bubba'd stock from my 96 Swede that I could use as a test.

What say you guys who have forgotten more about this stuff then I will ever know.

 

[682bear]

I don't know if bondo would be dimensionally stable enough... it may tend to shrink as it cures, or expand/ contract too much with temperature or humidity changes.

I always used Devcon plastic steel putty... the 1 pound can is enough for several beddings... but if the release is not applied properly, you will end up removing the stock with a hatchet.

-Bear

 

[wrat]

You ever see Bondo take a hit from a hammer?
That's what your bedding endures with every shot.
Sure, it's gooey and sure, it'll conform, and certainly it's easy to work with. No arguments.
Who wouldn't be tempted?
In bedding, the material has to be very strong in both impact (compression) and sliding (shear). Bondo is really neither of those things.
Polyester isn't really known for structural toughness.
Yes, it cures quicker. No argument.
But for a gun you'll hopefully shoot for years to come, what's another 12 hours? or even 24?
I'm sure someone has. Just isn't gonna be me - and I hope not you.
Plenty of other far more suitable materials - tried and trued and time-tested - that you can realize outstanding results from using.

 

[MikeInOr]

I use Bondo on painted woodworking projects a good bit; shop shelving, washer/dryer stand, etc. I have found it holds up better than I expected, 15 years under a washing machine with no signs of cracking. In such uses I have never had an issue with dimensional stability.

I would definitely go for something much stronger for bedding a rifle though! Like wrat said it is brittle and will crack if hit by a hammer.

 

[randyjaco]

It is probably OK in a dry environment, but if Bondo gets wet, it swells

 

[mickri]

I just threw this out there as another wild idea. A glob of cured epoxy is also brittle. Next time I mix up some epoxy for a project I will leave a glob to see what happens when you hit it with a hammer.

There are different types of bondo. They sell some in Mexico that dries to a green color. Rock hard when dry but gets soft from moisture. There is also bondo with fiberglass strands. And you can mix polyester resin with bondo to make it flow out better.

I plan to use epoxy that I get from US Composites in Florida. Or maybe West System. I have both on hand.

 

[JoatTX]

Typed all this up yesterday and forgot to hit post...

Bondo has some negatives when used as a bedding agent.

First of all it can be dissolved chemically by strong solvents, lacquer thinner removes dried bondo from surfaces quite easily, so some of the more aggressive gun scrubbers may cause issues if the inletting is not sealed very well.

Second, bondo is weak compared to accra-glass and devcon steel putty. The biggest issue is lack of compression strength, it tends to crumble and break when compressed (recoil lugs, behind receiver, etc)

Third is the porosity. Unless it is sanded smooth and sealed very well it will absorb oil and/or water.

Fiberglass resin thickened with flock is a better choice than bondo, but nowhere in the category of the devcon products, accra-glass, or Marine-Tex Grey.

Whatever you use as bedding don't forget the release agent. In the past I have used commercial release agents, Johnson paste wax, Pam cooking spray, and Kiwi shoe polish (neutral or tan, DO NOT use black) with good results.

Joe

 

[Madgepetto]

Bondo and it's various clones are polyester resin and fillers, usually gypsum dust or some other industrial waste.Polyester shrinks during the catalytic cure cycle and is very sensitive to moisture and solvents.Lousy stuff for bedding a rifle action.Better to stay with the epoxy based products that don't shrink and are blended to withstand recoil.

 

[DBlue]

I would definitely use Devcon for the bedding. I build custom .22 rim fire bench rest rifles and that’s all I use, works very well. I use Kiwi neutral shoe polish as a release agent, never had a problem using it. This is a bedding job I did using the Devcon.

 

[Firstram]

That looks great. Is that stock Purpleheart?