I know this isn’t Glocktalk but thought I would ask here.

I have a factory Gen4 Glock 21 and I have a new RDS Cut Gen 3 Slide. I want to build this out as a complete upper assemble maybe in 10mm or 460 since my Sig 227 idea hasn’t produced any good results. Plus everything I have researched says metal frame guns are not as good to do the .460 conversions on, so my 1911 will just stay a .45 due to frame cracking. Polymer guns apparently flex more so Glock 21s seem to be a preferred host.

Gens 3 & 4 use different recoil spring assemblies, which affects how the slide fits around the dust cover area of the frame. Cross Armory & Strike Industries are a couple companies who manufacture Gen3 to Gen4 slide adapter plates, but I'm uncertain if they work for in large frame Glocks. I can't find anything in product descriptions that say they do not.

https://crossarmory.com/produc...mes-by-cross-armory/

https://www.strikeindustries.com/si-g-sap1.html

I bought a generic one off ebay that hasn't given me any problems, although I haven't run it hard either. I don't think there's much to it. All it does is fill a gap.