Best material for modeling a part?

A

azredhawk44

Moderator
So... say I want to make an AR mag well insert for a caliber and magazine conversion.

What material lends itself best to a casting that can then be altered to accept springs, latches and pivot pins? A plastic? Epoxy? Some sort of resin?

I basically need to make a bunch of "blocks" about the size of a 20rd AR-15 magazine that has room to hold a 1911 magazine inside of it, and tweak each one to find the best depth for the magazine to insert, for reliable feeding. I will then take that plastic model and look into a CNC metal (probably aluminum) solution that is more stable and rugged.
 
I have seen plastic mock-ups of AR mags. Maybe you could modify one of those? If not, an aluminum block could be machined to fit the mag well very easily.
 
I GOT IT!!!

Is this an attempt at a CA legal AR with detachable magazine? What's the rule there, cannot accept in any way any magazine over 10 rounds? I'm not sure, but shooting from the hip it sounds like where this is going. Of course, I've been terribly wrong before.

As for what you're trying to do here's my suggestion. Take bondo, yes bondo and thin it with acetone. Remove the magazine release completely and tape up those holes from the inside of the mag well, don't want any epoxy to seep in. Tape off the top of the mag well completely, and then spray the inside very liberally with pam cooking spray. Make sure you use the kind that has olive oil. That will be the release agent. Then mix up your thinned bondo and slop it in. You will need to work the stuff in pretty good to get rid of the air pockets, and you will still have very small ones. Get a little wooden dowel to pack it in well.

In about 6 hours you will have a near perfect cast of your mag well that should be able to hold the springs, pivot pins, etc. as long as it's just a prototype. I wouldn't bank on it working forever but it should work long enough for you to experiment with and develope the specs to build something more permanent.

Bondo cures pretty quick... but thinning it plus making a solid block this big will probably take much longer to cure. I think I'd wait a day before I pounded it out. Just make sure you coat very liberally with release agent.
 
I GOT IT!!!

Is this an attempt at a CA legal AR with detachable magazine? What's the rule there, cannot accept in any way any magazine over 10 rounds? I'm not sure, but shooting from the hip it sounds like where this is going. Of course, I've been terribly wrong before.
Click to expand...

There's another good use for it... except I think there ARE 1911 mags that hold more than 10rds... big stick mags about 18" long.

Nah... screw California.

I just want an AR in 45acp that takes 1911 magazines, and I'm willing to put in some sweat and elbow grease to get it done. Once I have a functional plastic prototype, I'll look into milling a more permanent Aluminum solution and a possible patent or copyright, and maybe some sales later.

But for right now, I want a new 45acp carbine that takes 1911 mags, for me.
 
Delrin is easy to work with, though expensive if you are paying retail.

That Bondo idea is interesting though. Put some release agent wherever the Bondo touches...I prefer butter flavored Pam myself.
 
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