As I see the ramrod deal, breaking a rod is uaually due to too-loose a load causing excessive fouling buildup, whcih makes for sticking loads when trying to re-load.
The other scenario is that as DP says, hardened buckshot can also cause problems, but in my .32, loading the .323" hardened buckshot from Hornady with a .0215" patch, once they are in the bore and down 5" with the short starter, they go the rest of the way down with the rifle's hickory rod. They are must a little tough getting started with the oversize ball and thick patch as well, but - they go in and go down without breakage.