The Dasher is a mighty fine round indeed. I have been shooting one in 500m and 1000yd comp's for 3 years now, and dont have the desire to change.
I liked the caliber enough to have a varminter built in it.
Load development should be very quick and easy. Both my rifle with all projectiles used shoot very well. Just this week I loaded up some 65Vmax to do a quick ladder test. The rifle has a 1:8 barrel and a freebore of 0.114 which resulted in just enough neck to hold the 65Vmax in. Over 1.2grains of testing and 7 different loads, the group was 0.75" at 200m.
Everything I put in this case seems to work! The 1:8 twist still hammers the 65Vmax into nice groups!
The big surprise is how well the 87Vmax work out of mine. It will shoot under 1" at 300m, and has done so in competition.
Here is a couple of pictures of both my Dashers.
This one is my varminter, bipods can be fitted to front also.
This is the comp rifle
As for split necks or fireforming issues, I have had none. I use the false shoudler method.