Just some observations - bear with me.
First, for ordinary rifles, it is the hot gases that erode modern rifle barrels. During WWII Ordnance tested the efficacy of 8-, 6-, 4, and 2-groove barrels. They concluded that there was no accuracy trade-offs between 4-groove and 2-groove barrels, and 2-groove barrels were sufficient for the job, produced a significant cost savings, and thus authorized the production switch to 2-groove barrels for the 1903A3 Springfield. However, they also tested the barrel wear from the friction effects of the bullet passage, using both compressed air and powder as propellants, and found the frictional wear to be negligible with FMJ projectiles. Throat erosion from burning gases is the killer and allows a useful barrel life of 4,000-5,000+ rounds in the M1 with good accuracy, but actually up to 8,000 + rounds before the barrel is totally "burned out" and "bounces" down the barrel. However, many of the old-timers cautioned that soft steels, such as used in the 1873/84 Trapdoor Springfield dating from the late 1800's, can be quicly eroded by frictional effects when using jacketed slugs and high-temp burning smokeless powders. That's why I use only BP and cast slugs in the old smokepoles.(Ref: Multiple articles in the American Rifleman in the 50's and 60'). The Jouster.com Forums and its archives, regrettably now gone, discussed these issues in great detail.
Elmer Keith, who worked as an arms inspector at the Ogden Arsenal/Depot during WWII, has written that the S&W US M-1917 utilized barrels were made from relatively soft steels, and stated that the rifling could be worn out after 5,000 rounds of ball ammo. I have no reason to doubt his word on this, and certainly don't intend to test this in my Brazilian (at today's ammo reloading component costs, I can't even afford it!)
I have shot ten's of thousands of rounds of jacketed bullets through several of my post-war N-fraces (and 2-3X that in cast slugs), and have not found any eyeball-visible indications of barrel erosion from JHP/JSP use. Instead, I find the usual topstrap flame-cutting and discoloration of the forcing cone. In K models (19/66/13/65) the erosion from ejected burning powder particles in hot ligher-weight (110/125 gtn) bullets can severely erode the forrcing cone. As we all know, this led to discontinuation of the K magnum models and re-engineering to produce the beefier L-frames.
If there is to be any significant wear or damage to a magnum-chambered L/N/X barrel, I personally suspect it will be due to mechanical factors, such as copper fouling build- up that is not removed on a regular basis, and from other debris that might act as an abrasive.The forcing cones and breech end may show insignificant erosion. Only Ruger's 357 Maximum suffered significantly from this problem and was withdrawn from production.
Just a few other tips based on 39 years of S&W magnum shooting: The Lewis Lead Remover, still available from Brownells, does a great job of removing excessive fouling build-up. And continuous DA- and heavy max magnum load use will over time and many many thousands of rounds loosen up your favorite revolver. (And they can be rectifie).
BUT, go ahead and enjoy it- there's over 6 billion other two-legged critters on this planet who will never have the freedom or means to engager in this wonderful passion and pastime.
AND JOIH THE NRA!. PLEASE.
Cheers,
Sverre