Dear lonely friend of the 7mm BM:
You did right to take this barrel.
I use that chambering in a Mod. R93. Never shot bullets lighter than 140 grainers (Accubonds), most of my load development was around 160 & 175 grs Nosler Partitions. With these heavy-weights your very rare and in no way popular chambering 7-BM shows its full potential very clearly!
For Starting-loads take the maximum charge of 7mm RemMag data as a beginning. you can go far above that data toostep by step. Interestingly, working up full-house loads this way I got velocities with the 160/175 NoPartition without a problem. Eventually I landed at the same high level as commercial 7mm Wby loadings (home-made 7-Wby will do better with these heavies of course)!
measured velocities are topping the hardest 7mm RemMag loadings by 100-150 fps without any hocuspocus, this means a lot more high-energy-transfer on animals while reaching out, the 175/.284 bullets are extremely gentle rockets. by the way: my best 175 grain hunting load (NosPart) leaves the barrel at 3040 fps and shoots flatter than a 300 Wby with 180 grainers do).
Cannot say, if the chamber pressure in my loads is right on CIP-maximum (maybe), while the case extracts without problems and the primer pocket seems as tight as before I see no problem not doing so. The only bad thing could be the ending of the production for 7-BM brass because this chambering is not a commercial burner as well here in Europe.
Good luck while starting your self-made ammo, with a little patience you could become a very happy 7-BM hunter -
also very important for fitting the ammo in those tight blaser-chambers:
always use the same locking-head on your blaser!
greetings