I recently was gifted an unfinished Group Industries Uzi shell and want to give it a go since I have done a few AK kits with good results. My problem here is there are no press tools available anymore and I have no experience making press tools or jigs. Google mostly provides useless info about press brake cutting or heavy manufacturing that is not even close to the answers I need. Just tell me if I need 1095, O2, 416, 4140 or whatever, simple answers, not for a trained metallurgist. Anyways,  I'm going to make my own tools based off an old how-to guide from GI and taking measurements from a buddy's Action Arms. I need to know what materials to use that won't bend or deform under high pressure.

The two operations needing to be completed in a press are bending/straightening the front rounded trunnion section as it has a slight upward bow that needs to be aligned with the flat section. And forming the trigger group catch recess. The jig parts needing to be made are the top and bottom clamp plates for the receiver, I will just screw these together with many bolts down the full length of the receiver through the already stamped holes and off the rear for full support. For the rounded section, what is the best bar stock to use for the male bending die inside the receiver. I'll mill/grind a flat section on the top of this for the next piece, the extension to reach through the smaller section to press on the die, what should this be made out of? This piece may be able to overlap it's use with the trigger group forming die. The female support die on the bottom, can this be made from standard mild steel like the receiver clamp or should this be a better type of steel (and what kind) for not rolling the edges or deforming?

Next, for the trigger group catch, I haven't decided If I'm gong with a free floating set up for the alignment bar or a screw down type attached to the support base like the AK builder center support tool, but I cross that bridge when I get there. My main question here is what does the forming die bar that will actually form the recess need to be made out of? Also can the bottom support be mild steel or does it need to be upgraded like the round section lower support? I assume the type of materials for both set ups will be the same as they are doing the same jobs, bending the receiver without bending the dies and do the supports need to be harder so that they won't deform under heavy pressure. Hopefully the mild steel will work so I can make the receiver clamp and bottom supports out of one piece instead of making different set ups or having to use inserts. Thanks for the help.

For a one off press any steel you can harden or case harden will work.

I've made many many die sets out of mild steel and case hardened them with this.

https://www.travers.com/1lbcan-1-surface-hardning-compnd-kasenit/p/81-003-001/

Old world anvil used to sell it for their fly presses but I'm not seeing it on their site so above link is what you are looking for.

It will make a hard lasting die for more then just a one off.

Make sure your GI receivers are not twisted also.
That was pretty common having a twist or roll from back to front.
They make great UZI's once straightened out.
I made my mini from one and was able to cut the twist right out when I shortened the FS shell to mini specs.

I have every last document For the GI shell that D&D sold with the shells pm me if you need copies.
These make building them 100% easier then just trying to slap a shell together since there is some milling and everything gets set off the absolute zero point on the shell For weldment.

OP, register and take a look at Weapons Guild

They are a build site, my experience there has been very good, a huge number of build threads, experienced builders willing to help, and a large resource of blueprints and tool diagrams.

Join and find the UZI threads.