Back in the early 1970's before +P .38 Special loads became popular (they were restricted to law enforcement sales), I did a lot of PPC revolver shooting. Between a couple shooting buddies and me, we shot up some 2,000 rounds almost every weekend at practice and competition shoots. The loads were 148 WC and 158 RN standard velocity loads. I documented the firing of two new S&W M14 revolvers and found that they were just as tight and accurate after 50,000 rounds EACH as when new.
On the other hand, our duty revolvers (S&W M14 and M15) started to develop excessive cylinder gap and timing issues after a couple years of monthly qualification shoots using +P jacketed ammunition. That's three cylinder fulls each month, or barely 200 rounds per year.
Some police armorer friends verified this. For many years, duty revolvers firing only standard velocity lead bullet .38 Spl ammo seldom needed repair work unless abused by dropping or neglect. After +P and ++P .38 ammo became popular, the number of guns needing regular attention greatly increased.
If you really like your M14, be NICE to it and shoot only the mild stuff.
HTH
John