Herco is 1 of those overlooked powders that fall into the lighter end of the magnum class of powders.
Its burn rate is right there with hs-7, wsf (Winchester super field) & imr 4756.
Herco is at its best when it’s used in the manor it was designed to be used, “heavy loads”.

A lot of reloaders/shooters overlook these types of powders (as you can see by the different recommendations for other powders in this short thread) because they will use only 3 basic types of powders (lite, medium & magnum).
A lite powder= bullseye, hp38/ww231, AA#2 to name a few. These are all fast burning powders for lite/target loads.
Medium powders= unique, universal clays, AA#% to name a few. They types of powders are all a general purpose powders that do their best with standard loads.
Lite magnum powders= hs-6, hs-7, wsf, power pistol, AA#7, 4756 to name a few. All these powders tend to do their best when they are used to make heavy loads (p+ & magnum).
Magnum powders= 2400, h100/296, AA#9. They are best at what they are named after, magnum loads.

Herco is at its best in 9mm, 40s&w, 45acp p+, 38p+ ammo & the heavier the bullet the better.
A good example of its uses is in the 9mm:
A max load of unique & a max load of Herco pushing a 125gr fmj bullet or a 147gr jhp, the Herco will give you 100fps faster/over the unique with either bullet.

Why you’re looking at Herco, you might as well really look at Herco. Here’s something to think about (I’m going to post this same pic/question in the FBI load thread). There’s been a lot of threads lately talking about what powder buffalo bore uses for their FBI 38spl p+ load. A member on this forum had bought some ammo from bb & pulled 1 of their bullets apart to get a look at the powder they used & to weigh the charge of powder they use. The powder weighed 7.5gr & looks real close to Herco to me. Here’s a pic of Herco powder, note the dark bumpy flakes & the lesser light colored smooth flakes.



Here’s a link to the thread/picture of the bb powder.

Duplicating Buffalo Bore FBI Load

Just something to think about, it never hurts to keep a lb. or 2 of the lite magnum powders around. They can & will produce some highly accurate hard hitting loads at the economical price of a gr or 2 more powder compared to unique, hp-38 or bullseye.