I went to by powder yesterday told them I was loading 357mag/40s&w they sold me Herco. I can't find any load data for my 40 with 165gr fp. Can anyone help?

Older alliant manuals (7-1996 vintage) have some close data.

170 xtp they go 7.4 grains.
150 grns they go 8.2 grains.
180 grn JHP they go 7.0 grns.

For a 165 fp, I would use the 170 grn XTP as a high point and start 10% down. Work up over a chrono and aim for 1125 FPS for a 4" barrel.

If you are really hurting for data, herco loads "tend" to run about 10% more than Unique for the same bullet weight. Work up to Unique loads and then a "tad" more is probably safe. Be very very cautious though, you are really working with wildcats at this point since you are essentially making up data.

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SWCA 1646

You could try looking up Handloads.Com Load Data - Handloads.Com and entering 40sw and bullet weight. they have powder manufactures and contributing members data. Always start low and work up, of course.

In Pet Loads Ken Waters states that Herco is the unknown King of the 40 S&W powders. It is a book I suggest every handloader should own.

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Front sight and squeeze

I don't have any data handy, but I've used Herco in the 40 and got higher-than-expected velocities, a good clean burn, and impressive accuracy. I'd use it more often but it's one of those powders I don't see very often any more. I ought to try it in the 45ACP as well. Some shooters also regard it as the perfect powder for the 9mm as well!