I was reading an old article in the May, 1996 edition of the "Horological Times" discussing mainspring inspection and maintenance. In the article one of the faults listed in the mainspring inspection topic was "barrel bound". However, the author never explained what this meant. I've never heard this term used before, but assume they're referring to a situation where mainspring coil edges rub the confines of the barrel. Consequently, the edges of the spring coils are pinched and abraded (steel versus brass?) from rubbing against the barrel cap and great wheel.
I repaired a French movement once where someone had replaced the time train mainspring with one slightly too wide for the barrel. The clock would run very erratically because the edges of the spring coils were rubbing and binding. I was surprised the barrel cap didn't pop. However, I can't really say the edges of the spring were damaged; it was just too wide. More often, I run across coned mainsprings that bind and rub against the barrel cap as a result of being forcefully pulled from the barrel with pliers instead of a mainspring tool being used. Is that considered barrel bound?
I repaired a French movement once where someone had replaced the time train mainspring with one slightly too wide for the barrel. The clock would run very erratically because the edges of the spring coils were rubbing and binding. I was surprised the barrel cap didn't pop. However, I can't really say the edges of the spring were damaged; it was just too wide. More often, I run across coned mainsprings that bind and rub against the barrel cap as a result of being forcefully pulled from the barrel with pliers instead of a mainspring tool being used. Is that considered barrel bound?