Headspace on belt. Brass stretches, not many reloads, and it is expensive, long actions, bullet selection has improved in other calibers also. I have a selection of dies and calibers, if I won a 7mag, it would be sold.
On the reloading side, the headspacing/stretching becomes moot if you treat it as a beltless cartridge and headspace off the shoulder by means of FL die sizing adjustments or my favorite by using the Lee collet neck sizer. Some of my batches of 7RM brass have an excess of a dozen reloads with 160 gr loads in the 3000 fps regime.
+1.
My 7mm RM leaves a tiny scratch in the brass near the shoulder every time I extract a case from the chamber. I've had up t0 18 such scratches before I tossed the brass. Although I check the inside of every case every time I reload - just as I do for beltless cases - I toss the cases at 12 reloads with no signs of incipient case head separation.
As to popularity, it was all I had for 20+ years, at least in bolt guns suitable for big game. These days the kids are gone, their college paid for and I have 'invested' in a variety of other 'big game' rifles from .257 Roberts to .338WM in bolts and .30-30 to .45-70 in levers. All get used. Last year I used a 7mm RM and .280 Rem, this year I'm taking my .300WM and .338WM.
My hunting partner uses a 7mm RM exclusively.
Why not use the 7mm RM more? Too many toys, too little time.
