EA makes both cast and forged now, but in the past, before they shut down in '93, it is my understanding they had only cast.
HOWEVER, there cast receivers were the best, in my and many others opinions, on the market. Machining was good, parts fit, critical dimensions, etc, all good.
I had one, it worked well.
Main problem, most were finished in a medium gray, the mfg says matched the original M16 color, which it did. Problem is, there are no matching gray uppers now. EA offered A1 and A2 gray uppers way back when, but none available now.
If gray, you can use Norrell's Flat Black Moly Resin
www.molyresin.com to make it match current upper very well. I will be spraying and baking a local LEO's gray lower next week.
Ed to add, most were investment cast by Ruger's casting division.