The 1st Gen Universals, up to about serial # 99K, are GI compatible and often used some surplus GI parts. Mine is a 4-digit gun and came with an Inland slide and bolt, and a Rockola recoil plate, lol. I did swap in a GI trigger housing as the original was cast aluminum, and filled it with GI small parts. Since I had it apart, I also replaced the springs, restaked the piston nut, and adjusted the action hang.
It has been 100% reliable and is shockingly accurate.
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But ya, the 2nd Gen Universals aren't great- most seriously the stamped, skeletonized slides are well known for cracking. Despite this, people are asking crazy money for them, hoping to lure in unsuspecting noobs. Jack First even found it worthwhile to produce a couple runs of billet replacement slides for the 2nd Gen guns, but they were $$$$.
Interestingly, all of the Universals did use forged receivers- some of the only commercial carbines to do so.