Molding and Casting a Pistol Questions

I cut my teeth this past year on a one part silicone mold and casting. The mold and castings came out better than I expected so now I want to move up. I've been doing research on making a two part mold but I have a few questions.

I will (hopefully) making a two part silicone mold and resin cast of a pistol.

1. Would the barrel be the best place to pour resin from?

2. If so, should I add the spout when creating the mold?

3. Do I need to add a vent(s)?

4. If so, should add vents when creating the mold?

5. Should I brush in a bit of resin on each side of the mold then put the halves together and pour the rest in the spout?

Thanks gang!

Where are my casting specialists?

Everything but for question 2 is all if you want to. I imagine you're going to be making a two-part mold the typical way with laying a clay wall around the gun, yes? That's when you should add the spout and your keys just so everything lines up.

I will (hopefully) making a two part silicone mold and resin cast of a pistol.

1. Would the barrel be the best place to pour resin from?

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What type of pistol, Revolver or Semi-Auto? Are you wanting a solid, single piece or moving parts? Pictures of the piece will be helpful to advise the best course of action.

2. If so, should I add the spout when creating the mold?

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Spouts and vents can and probably should be made as a part of the master part. This way you can make them neat. You can cut them into the mold later if you have to.

3. Do I need to add a vent(s)?

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Yes. As you fill the mold, you need path ways to allow the air to escape or air bubbles may be formed due to trapped air.

4. If so, should add vents when creating the mold?

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Like the spout, I would add vents to the master part before pouring silicone. This way, you can plan them.

5. Should I brush in a bit of resin on each side of the mold then put the halves together and pour the rest in the spout?

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That really depends on the type of resin being used. Are you asking this as a type of seal or for 100% detail reproduction?
When I do my sole parts from clear, flexible polyurethane, I have found to get the best detail, I have to paint the inside of the mold with the clear ploy and then degas both the painted mold and the pot of polyurethane.

I'm casting a solid 1911 type with no moving parts. Thank you, you two for answering my questions!

on something as simple and basic as a 1911, for a solid one piece casting, I would use the bottom of the magazine as the pour spout. That can be sanded flat or a simple replacement of the magazine can be moulded and cast then glued into place. You want a pour spout large enough not only to pour material into but also allow the air inside to vent out while pouring. You can use the barrel to pour material into but youre in for a fun time getting trimming the part proper as well as hollowing out the barrel itself. A slightly off barrel hole ruins a perfect casting. For larger rifles and such where the barrel is actually large enough to use as a pour spout we would place a smaller sized dowel and cast that with the part. That way you have a perfectly sized and placed pour spout ready to go.

I both learned and self taught other ways to mould/cast items. Ill say the split board method is both a time saver and simpler method for casting items especially guns. You simply trace the shape on the split board and cut it out. Some paint sticks hot glued to the back secures the pistol to the split board (use painters tape on the gun wherever hot glue would make contact) then clay it in. If making a box mould the split board is secured inside the first half of the box for the first half of the pour. Its removed for the second half, part surface is prepped, second side of the box put in place, pour silicone. Of course lots of technique is left out but thats up to you to develop.

This was a super quick box mould of a rather large knife I did long ago but the premise still applies. This was literally about ten minutes of work from start to what you see here. Like I said, was a super rushed mould. Youll ignore the majority of the clay around the blade. Thats a trick I do to thicken the blade skipping the old methods I was originally taught. The pour spout was on the bottom of the handle. By default you want the path of least resistance for a pour spout. Something like a 1911 you may want to cut in multiple small channels inside the trigger guard for air to pass through.

robstyle said:

on something as simple and basic as a 1911, for a solid one piece casting, I would use the bottom of the magazine as the pour spout. That can be sanded flat or a simple replacement of the magazine can be moulded and cast then glued into place. You want a pour spout large enough not only to pour material into but also allow the air inside to vent out while pouring. You can use the barrel to pour material into but youre in for a fun time getting trimming the part proper as well as hollowing out the barrel itself. A slightly off barrel hole ruins a perfect casting. For larger rifles and such where the barrel is actually large enough to use as a pour spout we would place a smaller sized dowel and cast that with the part. That way you have a perfectly sized and placed pour spout ready to go.

I both learned and self taught other ways to mould/cast items. Ill say the split board method is both a time saver and simpler method for casting items especially guns. You simply trace the shape on the split board and cut it out. Some paint sticks hot glued to the back secures the pistol to the split board (use painters tape on the gun wherever hot glue would make contact) then clay it in. If making a box mould the split board is secured inside the first half of the box for the first half of the pour. Its removed for the second half, part surface is prepped, second side of the box put in place, pour silicone. Of course lots of technique is left out but thats up to you to develop.

This was a super quick box mould of a rather large knife I did long ago but the premise still applies. This was literally about ten minutes of work from start to what you see here. Like I said, was a super rushed mould. Youll ignore the majority of the clay around the blade. Thats a trick I do to thicken the blade skipping the old methods I was originally taught. The pour spout was on the bottom of the handle. By default you want the path of least resistance for a pour spout. Something like a 1911 you may want to cut in multiple small channels inside the trigger guard for air to pass through.

http://i56.tinypic.com/qozzw2.jpg

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Thanks Rob, I was hoping you would chime in. My plan was to do the split board so I did have a ton of clay sitting around. Are you saying with the big spout on at the magazine that there is no need for vents? Or did you mean cut in a few air vents on the trigger guard? Sorry I'm really new to this!

The red box is your pour spout. The red lines are potential non fill air pockets when pouring material so thats where you may need to cut vents. A tiny V channel cut with an xacto knife is best. The blue lines are extreme worse case scenario if those areas are still not filling and have air pockets. When pouring by default you want to slosh the mould around and tap or bang it a little. I use am somewhat rough on moulds due to the materials I use being a fast cure. I will plug the pour spout with a gloved thumb or clay then turn the mould completely upside down and all over mid pour then quickly pour the remainder then yet again flip it all around to further expel any potential air pockets trapped inside. Its all pending the material used for casting.

The front lower barrel red line may or may not be needed. I would start without that channel/vent and see what it says.

Awesome! Thanks for the visual, it really helped.

One more question, should the pour spout be the length and width of the magazine?

Sundowner said:

One more question, should the pour spout be the length and width of the magazine?

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It won't really matter. You can make it the full width. If you really want the detail on the bottom of the MAG, you can make a small open back mold of just the end and glue it the main cast later. As was said, the bigger the pour hole, the better the trapped air can escape.

I like how he tuned the gun with the front sight slightly down too. It is easy to see how the air can escape as the liquid rises in the mold.

cavx said:

It won't really matter. You can make it the full width. If you really want the detail on the bottom of the MAG, you can make a small open back mold of just the end and glue it the main cast later. As was said, the bigger the pour hole, the better the trapped air can escape.

I like how he tuned the gun with the front sight slightly down too. It is easy to see how the air can escape as the liquid rises in the mold.

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Thanks Cavx!

As he said, the size of the pour spout depends on the material. Too small a hole and the material will burp itself shut and choke. Although a coffee stir straw will likely solve that issue. As silly as that sounds, that trick has saved me a few times in the past when time was limited and clean parts needed. Just keep in mind all the air inside the mould needs to escape as material is poured in. Ive found a funnel shaped pour spout is much better than a full on strait through hole whether it be a box mould or bare silicone mould.

robstyle said:

As he said, the size of the pour spout depends on the material. Too small a hole and the material will burp itself shut and choke.

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Exactly. If you are pouring a resin like D65, you should be ok as generally this stuff is quite "thin".

If wanted to make a rubber gun, then your pour needs a bigger pour spout as this stuff is more like honey or much "thicker" and tends to hang up on the inside of the mold.

i know that I will need to clay fill holes, gaps, etc with a pistol but my question is how necessary is it that I need to try to fit clay in between where the slide meets the frame?

Here is a visual. I wasn't sure how much the silicone will make its way into the cracks. I know that its thick but I'm not sure how much I need to clay fill.

Just clay it in then smooth it out as deep as you like with a wood tool. You dont need to spend money on a clay sculpting kit in wood (not metal as that WILL damage the pistol surface) instead just get some wood dowel and smooth out the tool tips yourself. I have a cache of these for various jobs. They are super easy to make on a sanding wheel.

i have been using some plastic tool and wooden skewers lol. I never realized how tedious it would be filling tiny gaps with clay