The older the rifles, the oldert the steel specs, in the Lee line, the worse the stretch problem. My LM Mk. II (1894) stretches worse than the 1907 SMLE, it stretches worse than the 1918 NRF SMLE, it stretches worse than a Number 4, the Number 4 stretches worse than a P-14..... and I just don't know HOW to get a Ross to stretch its brass..... must not be using enough pressure, I guess.
The stretch issue gets worse with pressures, too. Keep to pressures relatively sane and the problem subsides. No hassle: you get the best accuracy (generally) with loads about 10% BELOW Mil-spec (which is a 174-grain bullet at 2440 ft/sec MV)
Nevertheless, case-length IS a big issue..... and case-length increases with stretch and so forth.
You really NEED something so that your brass doesn't get too long. You can get a little LEE case trimmer, lockring, stud and cutter assembly for about 10 bucks and it WILL do the job. This one IS important.
Keep your loads sane and you will get better accuracy, longer barrel life, less recoil and MORE FUN. Do you have any idea how much fun it is when you shoot a better target with a 70-year-old iron-sight warhorse..... and your buddy does with his superduperscopesightedlasercorrectedultramodern supersniper with the million-dollar scope? It's fun, believe me!
My rifles (P-14, Lee, Ross) tend to like eating the Sierra 180 flatbase, seated to the OAL of a Mark VII Ball round. Put them out at about 2250 ft/sec MV using a relatively quick powder: IMR 4895 is a good choice, my rifles like between 35 and 37 grains of the stuff, which is nice as I can get nearly 200 rounds out of a pound (on a total-disability pension, you don't buy a lot of moder powder a month, believe me!). I have had half-inch groups (repeated and repeated) from a Ross, 9/16 from an SMLE and 1 inch with a completely-original, absolutely untouched 1918 NRF SMLE, using this data.
SO: trim your brass, load sane and HAVE FUN!