Just to mention, when I started shooting Service Rifle ~20yrs ago, the guys mentoring me into it gave me a load for 55 ball over 27.3grn Varget to use as inexpensive practice ammo, even shooting this out to the 600yrd slow fire targets. I quickly stumbled into a high discount on 50 Vmax’s, and adopted the same charge under the new bullet. These were out of 1:7” twisted 20” A2 clones which were effectively required at that time for AR’s in SR. I’ve fired hundreds of thousands of rounds of this 50 V-max load in 1:7-1:14” 223/5.56’s, and loaded over 2m of them for customers while I was selling ammo for 3 gunners. No “overstabilization,” and no negative performance issues to report.
Surplus ball ammo, factory made, is as variable in quality as anything can be, but certainly isn’t representative of all bullets or all ammo sharing the same bullet weight.