I used THESE PILLARS.
Of course they need modifications to fit. They need to be shortened, the rear needs to be counterbored, the front one needs to be reamed as the front action screw is too big to fit through.... And of course the radius is too small to match the reciever for the front one. Some use flat topped pillars and bed on top of them...I'm sure that works fine and would have been much easier...I sanded it to fit by hand. [img]/ubbthreads/images/graemlins/shocked.gif[/img] Before I was done I was sure I was completely nuts.
By between the magazine and trigger are you talking about where the front of the trigger guard rests in my second pic? If so, I would say in most cases that shouldn't be needed if everything functions properly with it resting against the stock. But something you'll want to do before you mix any bedding compound is check function (magazine fit, feeding, etc) a bunch of times as you get close to the pillars' final shapes. Their depth and the angles of their bottoms locates the magazine relative to the action. If you hose it up it won't feed, the floorplate might not close, etc.
In my case with the bigger 300 RUM magazine, I found the best feeding happened when the trigger guard was slightly off the stock inletting. So I had to angle the bottom of the rear pillar such that it held the guard in that position. And in this case, no I don't think you want the front of the guard floating. Any sort of blow from rough use on it will cantilever on the rear screw and you risk breaking something. I wanted it to solidly rest on something. But putting the bedding there is the easy part and can be done after the main bedding job. The hard part is getting the angle on the rear pillar perfect so it places the trigger guard exactly where you want it.
Even without that problem it's sort of "nice" to have the trigger guard "snap" into place solidly when you put it on and not wiggle around as you tighten the screw. The McMillan inletting was enough wider than the guard there that there was some side to side play. That's your floorplate latch and if it's cocked to one side or the other it won't snap closed as smoothly. When I put in the bedding, I located the trigger guard in the inletting exactly where it lined up with the floorplate the best with a couple of really narrow strips of tape and let bedding fill in the sides where the tape wasn't. So now it only goes on centered in the bedding and there's no lateral play. This also makes snapping the floorplate open/closed feel a lot more solid.
As you can see, it's quite a job. If you want to tackle it, that's great. But keep in mind you can always send the works to McMillan if you don't want to take it on.