I've been trying to learn more about this fascinating piece of history, and something I haven't been able to figure out is what prevents rim lock. I don't see an interrupter like the Mosin Nagant or a large angle in the magazine like the Lee Enfield.
Theories I've seen included:
Cartridges have a rebated rim, which at least doesn't seem to be the case with 30 40
The rims are beveled, but given the massive sporterization, it seems unlikely that it would continue to work in so many different calibers.
There's a guide, in the exploded parts diagram I looked at, I didn't see anything that would act as a guide.

Magic?

'ShasVre' - Welcome to the KCA Forum. Actually, your question is a very good one.

I don't know for sure, but, I imagine with the 'doubling back', relatively light carrier/follower spring tension, and 'speed bumps', that Olle and Erik designed into the Krag-Jorgensen feed-path, the lead cartridge is momentarily separated, lifted, and moves in front of the cartridge following it.

They did work very hard on the mechanics and ergonomics of their action design. The first two 'Contracts', (Danish model 1889 and U.S. model 1892), were for rifles that utilized rimmed cartridges.

When you look at the drawings, the Krag action looks like a 'recipe' for rim jams.

I have never experienced a rim jam with a Krag, (or a French Berthier, for that matter).

It is very easy to have rim jams with a Lee-Enfield, if you don't carefully over-lap rims in the 'charger' with each cartridge rim in front of the one below it.
Then you have to orient and insert the 'charger' properly into the guides. (There is an 'upside' and a 'downside').

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Look down on the top of the receiver with the loading gate open.  The angle of attack for the cartridges is not ninety degrees from the axis of the bore's center line.  It is a bit more open let us say 100 degrees.  I do not know the correct angle.  I thought about this, too, in the past.  I took five cartridges and carefully dropped one at a time in the loading gate.  Each successive cartridge was always a rim thickness behind the previous one.

Even using the Parashooter/Steinmayer Deluxe Krag-Jorgensen loading charger I could not create rim lock.

Geometry -

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Thank you everyone, Parashooter, that diagram helped me a lot! It makes perfect sense now, but I wouldn't have picked up on that from the parts view. Such a remarkable design.

butlersrangers Magic is exactly how I've been explaining it in my head.

Nice explanation 'Parashooter'.

Hey, didn't Pickett's Virginia Regiments form into Line of Battle, by moving "in echelon", on the third day at Gettysburg?

In echelon? Oh, now I get it!

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They're kind of in echelon!  ;D

Lets stay on topic, this is not the "Chit Chat" page

I've had a few rim lock, but they've always been rounds loaded to a shorter OAL, like the Hornady 150gr FMJBT seated to the crimp groove.  That gets the OAL down to about 3.01".  Maintaining the angle parashooter illustrated, in the chargers makes the rounds stack in there the same way.

Chit chat or tit for tat, I'm confused!

Bumping the thread to the top of the board...
This thread was not removed, however there appears to have been some sort of indexing issue that moved the topic down on the board.

I've been using some brass that doesn't have the bevel on the rear.  Makes no difference in feeding and the chance of rimlock, in my opinion.  Looks to me like the only purpose it serves is to help get the extractor up over the rim.

'madsenshooter' - That's an insightful observation as to the the purpose of the 'rim bevel' on .30-40 brass.

I was thinking the bevel on the rim was dual purpose. If you have ammo that is shorter than GI issue can you purposely overlap the rims wrong? If so will the rounds still feed?

Someone spent a lot of time working out all the details on the Krag, I bet they woke up many times with solutions to all the potential problems.

The bevel is a little smaller on the Graf cases than Winchester or Remington anyone have any issues?

I know that some of the members here were using 303Brit cases when 30/40 were not available. Published photos show a smaller bevel on them, any issues with rim lock or extractor riding over the rim?
Anybody loaded shorter bullets that would not fit "echelon" and purposely align the rims wrong? Can you even get rimlock on purpose?
Curious minds want to know!

While sizing up the 45/70 cases for consumpter I tried on purpose to get a rim lock with my 35/40 cartridges. It is quite hard to do, aiming the barrel straight up and closing the magazine door slowly I could get it to lock up. When this does happen the front of the cartridge goes down instead of up into the chamber. I did not try really hammering the bolt handle to see what would happen.
Laying a couple of cartridges in the magazine with the gun level and snapping the door closed, the cartridges did right them selves and no rim lock occurred. The process is unseen and I can not explain why it happens.  With windows into the magazine and high speed cameras maybe you could understand what was going on in that dark place. Without the technology to understand what is happening, it is sort of like magic.

Parashooter's  drawing pretty much explains it with original length cartridges. With shorter ones who knows.

Interesting. At one point while playing with one of Paul's chargers I was getting them to lock with 150grFMJBTs at an OAL of 3.03".  At the short length the rim of the second round in the loaded charger would move ahead of the rim of the bottom round.  Occasionally, that position would carry over as the rounds went across the magazine and bang, it was stuck.  But more often they would self align on their way across.  A little tweaking on the charger got them at an angle that #2 didn't jump forward anymore.  Always that first round, I don't think any below it in the magazine were entangled.