The most common is a crack the starts at the internal corner of the receivers on either or both sides. Some have told me the weak point is the breech block as it sits behind the chamber unsupported. But all Marlin Ballards, cast or forged, use the same breech blocks, so if they were weak they'd fail in a forged action also.
I personally have seen both cracked receivers from some knucklehead chambering them in a high pressure cartridge, and blown up receivers from a possible double charge of smokeless, or just a too hot charge. When they blow up it's usually the receiver ring that lets go, and splits down either side, the top, or both places.
I personally have never had a Ballard receiver crack, or let go. I've owned a couple that concerned me, but never gave me any issues. One was a nice pistol gripped forged Union Hill in .38-55 that some clown cut right through the serial number on the bottom of the receiver ring, and put a cross screw through it to make it a takedown! I bought it for parts, but decided to shoot it a bit. I shot it more than a little, with average loads, and it was fine.
The other I still own, and it was modified when I bought it. It is the most unusual cast #2 I've ever seen, and is built like a deluxe Union Hill with pistol grip receiver, nickeled action, high end checkered wood, with horn tip forearm, and Farrow Swiss buttplate. Gorgeous little #2 that was originally a .32 Long, but somewhere along the line the bore got re-rifled to .316" groove diameter, and rechambered to .32-40 caliber. I shoot it a lot, but only as a breech seater, and with medium charges. I love it, and wont ever sell it; but if I did I'd pass along the usual warnings about not using hot loads.
It's the bottom Ballard in this old picture.
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