ginom I built a 6mm slr a few years ago for f-class and only did a bit of load development with it so far , the results were great lots of speed 3200 + with 105 grainers.
I really need to shoot this again and see what it can realy do at longer ranges , the results I got were groups around 1/2" @ 200 yds , I hear the competition match does the same as what the slr can do.
The 6mm slr is very easy to make brass for you just run a 243 in a 6slr die and it is done, it pushes the shoulder to 30 degrees and creates a long neck which is great for long bullets.