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Modelo Poly 43R Prep/Reloading Help (self.help)

submitted 1 week ago by Gajoso to c/help

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Currently working on the Modelo Polylactico and was wondering if anyone else had a good solution for sanding the longer Intermediate shells. I had no issues using a 6mm drill bit + painters tape shim as a mandrel for the Beginner 209 shells, but the Intermediates don't have enough surface area or depth due to their smaller holes to stay on the other smaller drill bits I've tried. I suppose I could force/tap an M2 or M3 screw into the top powder hole but would widening the hole cause issues if its sealed well?

I also noticed that the shell models had inconsistent rim thicknesses in Orca.

Headspace gauge/jig rim: 1.8mm thick
Intermediate .355 rim: 1.6mm thick
Beginner 209 slug and shotshell rims: 1.2mm thick

Obviously there would be an issue if the 1.2mm rims were used to headspace, preventing the thicker shells from loading, but wouldn't too much headspace also cause trouble like light strikes and case bulge/FTEs?

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[–] Bushworked711 4 points 1 week ago (1 children)

So, you seem like you are in the right track.

Use a 1/4" drill bit as a mandrel to hold the beginner shells for sanding.

For intermediate (or any upcoming load that uses small primers) you use a T25 Torx bit as the mandrel. I recommend a new one with crisp edges. You can also use the torx bit after smoothing the cases to ream out the primer pocket to size.

The beginner loads use a 209 primer. The 209 primers protrude out the back of the case because of the incorporated rim/flange. This makes up for the difference in headspace.

The headspace gauge is .2mm thicker than the shells (or beginner rim+209 flange thickness). This build with 43r Ammo is very forgiving with headspace. If you accidently used a beginner shell to headspace, you can just file some off of the breech end of the barrel, and file the extractor groove a little deeper. If you mess up and have too much headspace, you can sand some off of the front of the receiver to make up for it.

[–] Gajoso 2 points 1 week ago (1 children)

The man himself! Thank you for the info, I'll give the Torx a try and I'm glad the headspace is intentional. How are the other caliber Modelos coming along? I'm looking forward to building the .38 spl version after the 43R.

[–] Bushworked711 3 points 1 week ago (1 children)

38 special is going well. The armorer is testing it and hasn't really had any problems. 327 magnum has proven to be a handful. I don't regret choosing the 327 fed chamber, but likely we will recommend people go with the 32 h&r magnum chamber in stead. 32 h&r still used magnum powders, so you can really utilize the rifle length barrels. It is a very capable round, and the slight shorter chamber will play nicer with 32 long, 32 short, and 32 auto. I really like shooting the 32 longs out of mine more than anything. No problems other than the hotter 327 loads hurting the brass. The gun holds fine but the brass is wrecked with the hotter 327 loads.

[–] Gajoso 1 points 1 week ago (1 children)

Appreciate the update. I'm assuming that .357 mag isn't recommended if the hot .327 are causing trouble?

[–] Bushworked711 2 points 1 week ago (1 children)

357 is not going to fare well long term with the current design. Everything should be good to go for 38 special, even using +P loads.

I have a couple of ideas to reinforce the action, but printing the hammer and breech in CF nylon may be all it takes. I will get around to it eventually.

As expected, the optional steel safety plates do not reinforce the action. I have tried them on the 327 with no change in results.

[–] Gajoso 1 points 1 week ago

Sounds good, .38spl is very pleasant to shoot and cheaper anyway haha.

I'd be interested in the reinforcement ideas. The hammer looks like it could be cast out of a metal like Zamak. The breech might be too complex but I bet there is a way to cast it too, maybe in parts, then cleaned up using jigs like 80% frames/lowers. SCS inserts for contact surfaces could be an option too.