[greenr18]

Is there a compiled list somewhere of AR-15 caliber conversion uppers and what company makes said upper for said calibers?

[68wj]

I am sure there is, but some of the more commonly discussed from the ole' rememberer:

.22 Lr
5.7
.204 Ruger
6.5 Grendel
6.8 SPC
.300 BO/.300 Whisper/etc
7.62x40 WT
7.62x39
.450 Bushmaster
.458 SOCOM
.50 Beowulf

Then there are some WSSMs, BRs, shotguns, and LOTS of wildcats. For manufacturers, it depends. I know the 6.8 SPC has a good long list, and most of them also make the .300 now too.

[desidog]

^ that, and these too

-7.62x25
-9mm

[Saakee]

.45 ACP
.50 BMG (though not sure if this should count since it either uses a sideloading mag or is single shot)

[mongo4567]

5.45x39

[7.62 Nato]

6x45
25x45
25-223
7.62x40

[TXSWFAN]

Olympic Arms makes a 10mm upper.