Its a dandy for the .375 H&H.
^. Does very well in mine too. It's well balanced density wise. Fills the h&h case to the base of the bullet at max. charge.
It burns very similar to the 4350's, while dropping from the powder measure in ball powder consistent manner.
For me, that makes it a winner when one wants to load up a big batch, quickly, without the need to take the time to trickle every charge to weight.
Even made it work for bulk loading the /06 Garand. Adjustable gas plug vent added to keep the port pressure in line, .. 'n she purrs like a kitten into 1 3/4 moa from buddies sweet shooting SA.
Edit: to OP's 6.5x55 with H414.
It is quite usefull in this cal.. Load densities are a little shy, leaving a wee bit more airspace than I think is ideal, especially if you seat out to longer oal's.
That said, many 414 loads have stayed consistently sub moa with Nos. 120grBT's and Horn.140 IL's in my rifles.
RL22 has proved the most match level accurate 6.5x55 powder for me, but it's stick .. so you gotta weigh out every charge.