So, I was shooting my M4 Carbine today (SOCOM LE6920) and experienced a rather spectacular malfunction. I'm not sure what happened, but here's what the result was. Spent casing did not fully eject, and got hung up in the receiver, bolt overrode the next round being chambered and managed to strip another round off (I know it sounds bizarre). I cleared it by dropping the magazine, locking the bolt back and shaking loose two life round and the spent cartridge, which was all smashed off on the case throat. I've also had rounds being double fed. Could it be my Geissele spring and buffer combo I installed? The BCG is well lubricated, and bolt well cleaned, extractor is fine, etc.

Any ideas what's up? It happened once today out of ten mags put through the weapon.