Have any of you had experience with high impact resins? I've been working on a resin model of mine and it reminded me of the gun from "In the Line of Fire". I'm sure that this has been brought up before but I couldn't find any threads that related to this in my search. I've been stroking this idea for awhile in the back of my head and decided to just come out and ask. I've been looking at a few modeling resins but have yet to commit to a purchase, as they are pretty expensive. Also I have no real experience in this area and don't want to buy a bunch of junk.

So do you guys have any guidance in this area? I just bought a CD-ROM on molding techniques and I'm going to purchase a couple books on molding and car body work as they will have some guidlines on recommended products.

The gun from that movie was to me one of the ultimate "improvised" weapons that emphasized simplicity and lethality in a very covert fashion.

This resin would have to be able to withstand the impact of a .22 cal back blast. I want to start small on this first.

I don't know if there's a specific resin that will be this tough, but there's one used in GRP (fibreglass) manufacturing that might be hard enough if you use it in the right way.

I'm thinking of Furane Resin, and it's used by die-makers. Basically, to build the mould for any GRP object, you first build a wood or plaster original (the "die") That finally has a layer of fibreglass, and then many coatings of furane resin. It's a thinner, watery resin, but when it cures it's extremely hard, and can be polished to an almost glass-like finish.

You won't be able to use just this stuff, it will have to be a composite, but you might be able to get a hard enough finish by building up layers on a normal GRP base.

Its not really hardness you want - its toughness. Generally hard = brittle = shrapnel. If you choose hard resin for dimensional stability it must be reinforced. Try chopped glass fibre, carbon firbe, Kevlar, Spectron, Dyneema etc. Obviously glass is cheapest.

I was doing some research into GRPs, and it seems carbon fibre just disintegrates when pressure becomes too high, such as the impact of a racing car in a crash, which limits shrapnel but makes it seem like it can't be used in high pressure situations (beware - these are newbie grp thoughts, I am most likely wrong). Also, the book I read was saying that you really need to use epoxy resin with carbon fibre, which is more difficult to use, and may require the use of a vacuum chamber. Perhaps glass matting may be a better choice - you are only forming a cylinder, and so can lay it up properally.

Although I really do doubt you need to worry about a lot of this with a .22LR, aren't those crappy derringer kits made out of some plastic/pot metal?

Why not try machining a block of high strength fiber reinforced plastic, rather than resin casting?

Something like Zytel or Delrin should be adequate if you use a low pressure load. I'd go with a black power cartridge too, rather than a more modern smokeless, becaue of the lower cartridge pressures, meaning the gun is less likely to K-B in your hand.

I was thinking on a milling a block of plastic also, in fact as you suggest this might even be easier than molding. I guess once you get an image in your head of someone doing something that appears to work you kind of subconsiously gravitate into that thought. Although is a movie it really appealled to the do-it yourselfer inside of me. This will be a project that requires much more research before I actually get into testing. I figure that .22lr or even .22 short is a relatively safe cartridge to use, and is plentiful. I want something that is deadly at close range but also easy to find when your out in the sticks. Thanks for the suggestions so far.:)

Tuatara

You won't be able to use just this stuff, it will have to be a composite By which I meant a composite structure, faced with a harder material - the furane.

But I think in general people underestimate the strength of fibre reinforced plastics. Carbon fibre/Kevlar structures can disintigrate, but not without an enormous amount of force, and then only in the places where the force acts.

Ugh, sorry Arkangel. My brain must have been on the fritz when I read your post - no insult intended.

You're right about underestimation of material strength - it applies to many things besides resin/fibre composites. Probably due to the different failure mode - most common metals simply bend, and stay bent. Composites seem to leap straight to catastrophic failure - e.g. some of the carbon composite yacht masts that exploded in the America's Cup.

Yet the flywheel power backup system I was involved with once had a 10kg flywheel running at 40,000 rpm - only held together because of the outer wrap of carbon fibre. Nothing else was strong enough.

While I realize that this is my fourth post and this has already been brought up I still would like to offer my advice.

I beleve that Carbon Fiber would be your best bet. Upon doing some quick research on Google I have found several links regauding carbon fiber tanks used in Hydrogen Fuel Cells. Several of the takes are constructed completely of carbon fiber and then coated in a fiber glass. These tanks can support pressures of up too 10,000 PSI.

OK well thats my $.02 hope it helped some.