I was looking through the St. Croix blank lineup to find a blank to build a fairly soft casting rod with. This is basically to throw light spinners and crankbaits with. I was eyeing the 2C66MM rated for 8-14lb 1/4-5/8oz. Then I looked at the 2C66MF rated at 10-17lb 1/4-3/4oz. Just for kicks, I checked the 2S66MF with is rated at 6-12lb 1/4-5/8oz.

So to summarize:
2C66MM 8-14lb 1/4-5/8oz
2C66MF 10-17lb 1/4-3/4oz
2S66MF 6-12lb 1/4-5/8oz

Looking at the numbers for seemingly the same lure size ratings and power ratings, why the different line ratings? The most significant difference is between the fast action spinning blank and casting blank. What is the difference between a St. Croix casting and spinning blank that is rated for the same power? Are they different actions?

Ryan

With St. Croix, these are, in fact, often different blanks. Not just the same one listed under two categories. Select the one that suits you best and don't worry too much about whether it's listed as casting or spin. I find their casting models to a bit stouter in the tips than the very similar models in spinning.

.....................

If you look at the specs, butt & tip diameter + weight - you can get a decent idea on whether it is the same blank or not. GRanted, it is not definitive. I kno wLoomis used to have the same Musky blank sold for $30 more listed as a SW blank.

I find that most crankbait fisherman prefer the moderate action over a fast tip. the SCMM is a medium power, moderate action blank. Might be a better choice for cranks.

I agree with Tom K that St. Croix does tend to make their "casting" blanks a bit more powerful than their "spinning" blanks. (In fact, I have "cross-built" on their blanks in both directions when I wanted a little different power. But, and a big but, the line ratings reflect more the type of reels that will typically be used on these blanks, the differences in power are nowhere near the differences in line ratings. The lure ratings, on the other hand, are a fairly good gauge. (All the above is about power, not action.)