I've been shooting Dashers since getting my 1st one in 2004; to begin with, we all used Varget. I was happy with the accuracy & velocity, but couldn't help noticing how rough that 1st wet patch felt when pushing Varget fouling out of the bore. I had an 8lb jug of Viht N150, and because it was listed as slightly slower than Varget, decided to try it. I never got an appreciable amount of extra velocity with it, but the accuracy was at least as good as Varget, and QuickLoad shows it has an appreciable lower flame temp than Varget. At that time, I was loading 34.5-35grs of N150, but over the years, the burn rate of N150 seems to have gotten faster, and with recent lots, I'm not able to load any more of it than of Varget - around 32.5grs.
I'm also a fan of IMR 4007SSC, but have only tried one load in one of my current Dashers. Will be working with it this fall/winter to see if accuracy potential is as good as Varget. I'd bought a couple of 8lb jugs of it years ago, and had used quite a bit of it in a couple of 6.5x47s - mostly with 123s - with great accuracy. Wasn't all that crazy about spending time working with it, since IMR discontinued it, but recently found three more 8lb jugs at a very good price, so with 32lbs of it sitting around, I need to find a good use for it.
Several of the guys I know who shoot Dashers in PRS matches are using H4350 and getting very good accuracy with it. I've personally never loaded H4350 in anything I shoot, but am getting ready to dive into load development in the Dasher with RL16. It's pretty bulky for such a small case, but I've got a homemade drop tube that works wonders when it comes to getting powder kernels to settle. Copied the design for it from an article in Precision Shooting magazine years ago, using some hobby shop brass tubing that I annealed to dead soft condition so it wouldn't kink while putting the bends in it, and some clear acrylic rod for the ends. Will try to find a photo of this drop tube to post up - need to organize photos I have on the hard drive on this computer & USB drives so I can find what I'm looking for without spending an hour looking...lol