12 ton press, nice, but not necessary.
Spot welder tongs, nice, but not necessary.
Rivet crusher, nice, but not necessary.
Flat bending jig, very nice, but not necessary.
Think outside the box comrades. You're not building a precision rifle for Ivan so odds on you have most of what you need right now.
I got dragged into the build sickness by my sons. Oldest had just gone active and we were at a gunshow where Romy kits were $60. His comment to me was if some haji in a cave with rocks and stick could fabricate one, we could surely do so in the basement with minimal tools. That was the prompt, minimal tools. The boys both bought multiple kits and flats to embark on the great experiment. And yes, we did experiment with screw builds. They work, but I prefer the rivets.
12 ton press. Nope, just need some dry ice, MAP torch and bench vise. Apply heat to trunion (this was back when the barrel was included) use cast off piece of steel for drift, use big bench vise as press to pop the pin out. Bed barrel assembly in dry ice (or freezer) for a day, heat trunion with torch, rest in top of jaws of vise, drift out barrel with brass drift contoured to fit barrel and chamber. Sounds way harder than it really is.
Flat bending jig. We used 2 pieces of scrap steel bolted together with the edge where the fold would be. Chuck steel into vise, use brass hammer to start working the fold. Repeat for other side. Yes Virginia, this will work with patience. Repeat for top rails.
Spot welder tongs. Don't needem. Use scrap steel filed to thickness for location of ejector and rails. Drill hole in receiver at rail location. Clamp rail into place. Plug weld into place, filling hole.
Use barrel trunion to mark hole location for rivets. Drill receiver for rivets.
Rivet crusher tool- Only if you're OCD about appearance. Bucking bar made from rail road spike and hollow nose punch (made from center punch with grinder and dremel). Using hammer and punch, pound rivets in place, takes time and some patience, still looks ok, completely functional. The first couple will look odd, you'll get better as you do more. Only folks who would object are those who want perfection in appearance. But remember comrade, perfect is the enemy of good enough.
Put barrel back into freezer for at least 24hrs. Heat trunion (riveted to receiver) with MAP torch, not red hot, but hotter than you'd ever think of holding it. Lightly grease barrel and insert into trunnion. Line up hole for pin before it can lock into place. Drift pin back in. If the barrel and trunnion were already an assembly, the headspace will most likely be fine. Still need to check it. If using a new barrel, it still has to be populated and it's possible using this method, you just gotta have patience and be meticulous.
Bottom line, we assembled a number of comrade K's goodies using nothing more than a bench vise, some drill bits, a rail road spike, modified center punch, hammer, MAP torch, some scrap steel.