There are some jacketed soft point bullets that closely resemble the shape of the standard ball ammo. I'll try to dig some out later tonight to give you specifics. The closer you come to the original load the better you can expect the cycling to be. Moving to a soft point will improve terminal performance, obviously.
You can squeeze a little more accuracy out of the carbine, but it's no 'sniper rifle'. A little acra glass under the lug on the stock where the rear of the action hooks in does wonders. That little bit of slop between the wood and the metal lets the action shift a tad under recoil. Bed that little lug and you will (usually) notice a little improvement for verry little expense or time.
Kahr is making new M1 Carbines. Last I knew (a few years ago) they were in the $600 range. Not a collectable, but a brand spankin new US made gun. Not bad, I thought.
A little side digression on the .30 carbine round. About 15 years ago I was at the SHOT show. One evening I met a gun designer from Isreal and we got talking guns. (quite a bit of gun talk happens at the SHOT show) Anyway, he was there promoting his new gun which was a little bullpup in 30 carbine. He was telling me all sorts of benefits of his new gun. I asked why he chambered it in 30 carbine, which is kind of looked down on among rifle rounds. He told me that US gun writers and other such experts poo-poo the 30 carbine round but in Isreal it's well regarded. They have lots of trouble and the 'collateral damage' may be the soldier's own family. It's a built up place and you sometimes have to fight hard people in areas with families and homes. Not good. The 30 carbine doesn't go as far as 5.56 but punches vehicles and vests better than any 9mm ever will. His design didn't become as popular as the P90 by FN (I've never seen this guy's gun since that show) but the principal is strikingly similar. Point being, 30 carbine is not a cork gun. Loaded with soft points you can take some game (I'd go bigger for bear) and you can expect better penetration than an auto pistol will give you and a better hit probability on targets beyond pistol distance.
Lots of writers dismiss the carbine. None of the old timers I've known who carried one for keeps (including my grand father in the Pacific during WWII) seemed to dislike it. I was once told that the M1 carbine is small enough and light enough to reach over the top of a hole and shoot one handed and powerful enough to do some damage when it hits; while still being good enough for some aimed shooting like a rifle. It doesn't stack up favorably against a rifle, but it's way better than most submachine guns. Now, that doesn't really translate well into today's civillian world of shooting (I'm not about to shoot one handed at targets I can't see well) but it was an observation shared with me by a man who came by it honestly so I figured you may like to hear it too.