Yes, the 135 MK 270 bullet does well. I have friends who hunt with them in their light weight carry in Sendaro rifles chambered in the 270 Cal.
You are about maxed out at 1000 yards with them if you try to stay above 900 to 1000 Foot pounds of energy. That's why most Longrange hunters like the heavier weight and higher BC bullets so they can reach out even further and with more energy.
If you have a 270 with a longer barrel to increase the velocity, the 135 MK or the Jenson bullet would work quite well. Check with Warren as per the twist and land configuration you may need in your barrel.
Your barkin right up my ally. I've been using the 135MK on whitetail for the past few years and for the first time at longrange this past season. It has yet to show me any reason not to use it.
As for the J36, well I just started load developement back in january. First results were pretty damned discouraging but I haven't given up hope yet. I'll have to do a little tweekin with seating depths and powder charges, but a 3" 200yds group was not what I was expecting. But then again I believe that it was Warren who told me that his bullets were more likely to preform best in factory barrels (tad on the lose side) vs a custom barrel (a little undersized). Well I got to go so I'll talk at ya later.
Actually the j36 didn't seem to foul any more than the other bullets. As for velocities, I didn't have time to set up, but suspect that I was getting slightly lower than the 135MK. Point of impact was approximatly the same. The load that I was working on that day has since clocked a just below 3800fps. That seems to be right around the most accurate spot for the MK. In colder weather I had pushed it up further but think that I will keep it between 3750 and 3800, no need in pushing it further.