I found a conversation I had with a guy a long time ago when I started reloading for my 7mag and then now 2 7mags (Tikka T3 and Browning Abolt II). So some of the verbiage will apply to having 2 rifles, and the process involved to incorporate both rifles.
Dialog:
Learned a long time ago that belted magnums were to be loaded just like standard cartridges, where they headspace off of the shoulder instead of the belt. Once you figure that out, you are golden. So in your case, since you have 2 different rifles chambered for 7mm RM, I'd use something to measure to the datum of the shoulder of the fireformed brass. Compare results between the 2 and hope they are close. If they are within .002-.003", you will be fine to load to the shortest chamber with a bump of .002". Then the brass will chamber in each rifle and not cause an excessive amount of case stretch. If the rifles chambers are not real close in measurement, you may need to segregate your brass. Which you already know and mentioned in your thread. The pictures I posted show what it may look like if you size your brass with a .002" shoulder bump. You can see where the die did not size the neck all the way down. You can also see that the shell holder is quite a ways away from the bottom of the die. That is known as a PFL (partial full length) sizing process and I do that with all the cartridges I load for. Here's an outline of how I'd tackle your situation:
1. Fireform at least 5 pieces of brass from each rifle. That way if you oversize one, you can set it to the side.
2. If you don't have a comparator, like the one I pictured in your thread, use a 40 S&W case to measure to the shoulder on your fireformed brass. Someone in your thread suggested using a 9mm case. That is too small. This can be tricky, because you want to be able to measure accurately. You may need to slowly spin the 40 case as you take the measurement. That ensures it is sitting squarely on the shoulder.
3. Now, to set up your die: Adjust the die so it is off the shell holder like in my picture. Test it in your rifle. The first time, it probably won't chamber, if you do it right. If it does not chamber in your rifle, turn the die in 1/2 a turn and check again. If it chambers with resistance you know you are getting close. You want to keep turning the die in (maybe a 1/4 turn this time) until there is a slight resistance on the bolt when chambering. Take a measurement and see how much the shoulder is being bumped back. .002-.003" is what I look for. Then test the die setting with a different piece of brass (one of the 5 you fireformed from that rifle). I like getting a good average, so I use a few pieces of brass as a check, to make sure the die is set about perfect.
4. If you are using RCBS FL dies, do yourself a favor and buy some Hornady Sure-loc lock rings for your die sets. I prefer the RCBS dies though because they have a breather vent hole, that reduces your chances of denting the shoulder from too much sizing lube.
5. I forgot to mention to wipe the sizing lube off before you test the sized case in your chamber. Then re-lube when you are sizing (of course).
6. When you are done, your die will be adjusted properly and the newly sized brass should chamber nicely. Your brass will last a lot longer and you will have to trim less frequently.
Now after doing this initially with my pile of R-P brass, I took half for the Browning and half for the Tikka. Because once it was shot in either rifle, it was fireformed to that specific chamber. Just for giggles, I tried swapping the brass to see if the chambers were close and neither of them would close the bolt on the other. Which meant the chambers were different. So now they have dedicated brass for each rifle. Hope this doesn't confuse you.
