How to cast non-metal firearm parts?

[Ds J]

Hi Folks,

I consider casting a copy of a wooden shotgun forearm.

My shotgun is a clone of the Browning Auto-5 and the wood of the forearm tends to crack.

If I can make a copy now, while the wood is still very good, I can use the copy and save the wooden piece. They are almost unobtainable in SA, and I simply wouldn't have time to make one.

One idea was to have it 3D printed, but Bushmunki advised me to rather try casting.

Any idea or suggestion as to the material, process or any other things to keep in mind?

[oafpatroll]

I'd suggest making a mould and then making the part from fibreglass

[Treeman]

There is a modeling material that you can pour around things and then peel off, its like a hard latex. You coat item a few x and then at an easy to finish off corner or end you cut it open and peel mould off.A ex girlfriend of mine used it for  just that in art, making casts of things - often for pregnant woman.

On things like the stock u mention, the item would be moulded, peeled, then filed and allowed to set. Then the filled set mould would be put in a box and the box would be again filled with a hard resin. The box and the cast part would then be sawed with a thin blade in precisely the center, two halves matching. Then the box would be drilled and aligning pins pushed through. A fill and breather hole or 3 - 4 would then be drilled.
Almost anything symmetrical could be copied this way. 

[Newton]

Any idea or suggestion as to the material, process or any other things to keep in mind?

Why not get a proper wooden gun stock maker to make you a laminated wooden piece
A good stock-maker will have a replicating machine - it can cut a copy of an example to close tolerances - and then finish off by hand.
Stay standard with wood.

[oafpatroll]

Another option if there is some clearance on the inside of the wooden forend is to directly reinforce it with fibreglass to prevent it cracking in the first place. A mm or two of glass properly bonded to degreased and keyed up wood makes for a very strong and stable laminate and still look original.

[Treeman]

Another option if there is some clearance on the inside of the wooden forend is to directly reinforce it with fibreglass to prevent it cracking in the first place. A mm or two of glass properly bonded to degreased and keyed up wood makes for a very strong and stable laminate and still look original.

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Yes and you can get the tissue fiber glass, its like lace its so thin and its "moer" strong when glassed. VERY very good suggestion this. Glass is almost forever.

[Ds J]

Hi Folks, thanks for all the suggestions. This is the nice thing about forums - one question leads to several good answers I have not considered yet.

Any idea or suggestion as to the material, process or any other things to keep in mind?

Why not get a proper wooden gun stock maker to make you a laminated wooden piece
A good stock-maker will have a replicating machine - it can cut a copy of an example to close tolerances - and then finish off by hand.
Stay standard with wood.

There are several options why I consider casting.

Casting would be diy - I get to learn something new. Working by hand is a very good break from really tiring daily work. (I have been working on a single chair for close to three months. Everything from the wooden stump down to the final product.)

The casting process should theoretically be faster and more cost effective than anything with wood.

If the plastic breaks or scratches, I make a new one.

One should be able to pick colours.

[oafpatroll]

While restoring old vehicles I've dabbled with casting things like unobtainable lenses for old car lights and replacement sections for bakelite encased steering wheels. From that I learned it's a fiddly process and definitely not cheap if you want a solid and robust result with good finish. There are more casting materials than you can shake a stick at and they have properties that make them more or less suitable for particular applications.

Having looked at pictures of the forend I think you'd need to build a minimum 2 part mould, maybe even 3, with stepped tubular inserts for the mag and possible barrel channel too. That's certainly doable but not the easiest thing to start with.

If you do decide to go ahead with a monolithic cast I'd suggest speaking to the tech guys at AMT Composites (011 392 4232) for some advice on your application. They'd be able to suggest an appropriate casting material and reinforcing admixture/s. Given that it would be quite a complex mold with inserts and so forth getting their input on appropriate release agent/s would be a good idea too.

Having got through that shpiel I would definitely go with fibreglass reinforcing the existing wooden stock internally. Process would be pretty much the same as epoxy bedding a rifle stock, i.e. you'd relieve the wood a couple of mm, degrease the hell out of it and then apply epoxy and glass and clamp the lot to the heavily release agent coated and polished action. I'd do it in two or three steps to ensure that I didn't lock it up on the complex shapes and I would not go into the enclosed section of the mag tube.   

Good luck with the project and let us know how you get on.