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I know that some years ago rimmed cartridges were used in semi-auto rifles, but I don't think they are in modern semi-autos. Is this because the rims cause them to jam, or what?

Crash

I assume it's easier for the extractors to grip the ridged indents in modern semi cartridges. Also easier to stack them in a box magazine...

My 7.62x54R Molson uses a rimed cartridge. When inserting cartridges into the magazine, you must insure that the rim of the last one inserted is in front of the cartridge under it. If the rim is behind the cartridge will not strip out of the magazine and you have a jam.

In America it's probably because John M. Browning concentrated on rimless semi-auto designs after designing some semi's that used rimmed and semi rimmed cartridges. "If it didn't break don't fix it" to morph the old saying.

Don't the Dragunov sniper rifle and PKM machinegun chamber the same 7.62x54R rimmed cartridge that the Mosin chambers?

The Annoyed Man wrote:Don't the Dragunov sniper rifle and PKM machinegun chamber the same 7.62x54R rimmed cartridge that the Mosin chambers?

I think both the British and the Soviets have/had rimmed semi-autos. I guess it depends if the 1960's is "modern".

The Annoyed Man wrote:Don't the Dragunov sniper rifle and PKM machinegun chamber the same 7.62x54R rimmed cartridge that the Mosin chambers?

Yes, but the 7.62x54R has been around for what, close to 100 years?, so I don't consider it a modern cartridge like the 7.62x51 (which itself has been around for more than 50 years...). But when you look at modern American hunting semi-auto hunting rifles, I don't think there are any that fire rimmed cartridges.

Crash

The Annoyed Man wrote:Don't the Dragunov sniper rifle and PKM machinegun chamber the same 7.62x54R rimmed cartridge that the Mosin chambers?

Yes. https://en.m.wikipedia.org/wiki/PK_machine_gun
https://en.m.wikipedia.org/wiki/Dragunov_sniper_rifle
Also think about the steep incline on 22 cal LR magazines to insure that he rim doesn't hang up when feeding.

I think it is largely because you can't stack rimmed rounds in the magazine in the same way you do with rimless cartridges. I have seen semi-auto rifles shooting rimmed rounds, but they almost all use single stack magazines and have limited capacity. I think rimless cartridges just stack and feed more reliably in semi-auto guns.

I have a Coonan 1911 in 357 Mag. The mag holds 7 rounds in single stack, but they are angled to insure the rims don't interfere with each other. Same thing with the Keltec PMR30. It holds 30 rounds, but you have to be careful loading the mags.

Well the Russians, British, Japanese, Siam and some others, all used rimmed cartridges in their rifles, machine guns, etc. But as already mentioned you have to be careful loading a magazine so that the rims don't overhang each other. If the round underneath has its rim in front of the top round, you get a misfeed. That also limits the rounds to single stack magazines and reduced capacity then. Since the rim rests on the bottom cartridge it causes the angle or curve with the rounds in the magazine to be more extreme thus limiting how many you can use in a magazine. The machine guns could be belt fed or like the Japanese did with the weird metal stripper clip. Thus the more modern guns all went with rimless cartridge designs which improved reliability then. I think that the Dragunov was probably the most current rimmed cartridge semi-automatic rifle made. But since it was a sniper rifle, the user would have been trained better than the regular troops and thus it was likely to not be a issue with them getting the cartridges stacked improperly in the magazines.

There are a few 22 Rimfires and Ruger 44 magnum carbines.