PRVI Partisan soft point ammo is excellent, with consistent accuracy and excellent terminal performance. Agree with replacing the magazine catch which has an extra shoulder to hold the 30 round mags in place during recoil. Keep the extractor clean and lubed before you go complaining about aftermarket mags (been there done that.)
Yeah I was spared the 30 rnd mag reliability headache by my uncle (FBI certified firearms instructor, former NSW vet, former LEO and all-around savage) on that and more.
The M1 Carbine is very underrated, IMHO.