A while back, I had one of my reloaded 9mm rounds fail to chamber in a "Glock 19 compatible" barrel. That got me to wondering if there were significant differences between barrels, and if a barrel swap might fix the problem.
So happens, I had five Glock 19-type barrels, plus a Glock 23 9mm conversion barrel, ranging from a $200 Wilson Combat barrel to a 'no-name' barrel I got for $15 on GunBroker. I tried dropping one of my reloads into the chambers: some chambers were 'tight', others were not. I expected the WC barrel to be the tightest/most problematic, but it wasn't - that honor went to a couple of Palmetto State Armory barrels. The most 'generous' chamber was on the inexpensive GunBroker barrel, with the expensive WC barrel in the middle of the pack. So I use that inexpensive barrel when I'm shooting reloads, and have had no more problems.
Point being, barrels chambered for the exact same cartridge can run tight or loose, depending on design, reamer specs, reamer wear, QC, etc. And I'm sure different ammunition manufacturers turn out ammo with different dimensions. I weigh my 9mm brass, and individual cases vary in weight from the low 50s to the mid 60s (in grains); rim thickness & case wall thickness also vary, and you can bet that bullet diameter can vary 0.001" or more. And with a 'tight' chamber, even 0.001" might be the difference between reliable functioning and constant hangups.
No idea where Ruger is sourcing their RXM barrels - guessing most of them are fine, because Ruger is a reputable company. Maybe some issues are more the result of variations in factory ammunition - I was just reading some complaints online about some Norma factory ammo, so even products from reputable ammo companies may not function reliably in some firearms.
As always IMHO, FWIW, YMMV, etc., etc...
