All my precision rifles run moly bullets.
That includes a Krieger-barreled M14NM, Colt Competition HBAR, Remington 700PSS, and 6.5-06 Interdiction wildcat, and WWII Remington 1903A4. I competed for several years with the M14NM at High Power matches, and the gun never experienced any ill-effects from the moly coating of bullets. Neither have the others. For a time, before I just got lazy, I moly-coated ALL of my centerfire jacketed handloads, to include 7.62x39, 7.62x45, .30-30 Win, 8mm Mauser, and .32 Remington. Once I find some extra time, I will get back to doing that. My old 8mm Mauser barrel looks like 20 miles of bad road inside, and the moly coating did indeed keep things from coating the insides. I'd change the barrel, but it shoots so well...
The most noticeable difference happened in my 1000-yard 6.5-06, which I always ran on the ragged edge of pressure, using thick RWS 7x64 Brenneke brass. It had a beautiful Krieger barrel, but was always laying down copper fouling in the last inch or so of the 25" barrel length, be they Sierra MatchKings or Nosler Ballistic Tips. The 3200+ fps probably contributed most to the copper fouling. Moly took care of that, and also dropped pressure signs on the brass. I make no attempts to remove all of the moly in that barrel during my cleaning sessions, and will continue to use that technique as long as I have a few pounds of lab-grade moly disulfide powder at my bench.
Moly will deposit elsewhere in gas guns, by the way. The piston face of my Bulgarian AK shows a thin coating of moly after about 60 rounds or so. Same for my M1 Garands. I'm sure if I ever take the gas tube out of my AR-15 or AG42B Ljungman, it'll be there, too.