My perspective is a bit dated, but I remember back in the early 90's that the M9 had a finite number of rounds you were allowed to fire the weapon before it was "expended." It seemed at the time that there was a tendency for the slides to separate from the frame during operation after several thousand rounds. Not a big deal when you are only using them for war, but what about training.
I was part of a weapons training program for midshipmen at the Naval Academy and some of the brass started wondering why we weren't training with M9s. The summer training program for the incoming plebes required about 60 pistols. If we had used M9s we would have had to throw the 60 M9s away at the end of the summer. Instead we continued to use the same national match M1911s which had been used for years.
On my successive deployments to the Persian Gulf we did one cruise with 1911s and then got a SIG 9mm I think that is the M11 for the second cruise. The SIG was a really nice pistol, relatively small and easy to operate. Pretty accurate right out of the box, too. Didn't think that much about stopping power, just assumed you would have to shoot your targets twice.
If the Marines want a .45 I say give it too them. They are the only service left that pays attention to marksmanship. Marines can handle the big guns. I hope people have taken note that as the Army has jumped all over the M-4 carbine, that the Marines are still buying long barreled M-16s.
I was part of a weapons training program for midshipmen at the Naval Academy and some of the brass started wondering why we weren't training with M9s. The summer training program for the incoming plebes required about 60 pistols. If we had used M9s we would have had to throw the 60 M9s away at the end of the summer. Instead we continued to use the same national match M1911s which had been used for years When I was a match armorer at the Naval Weapons Support Center small arms shop at Crane, we got all the Annapolis training guns, .22 conversion kits fitted atop .45 frames, for rebuild. Some of those guns had been reassembled on NM .45 frames, some were on Colt commercial frames, and a few on old M1911 frames, which were replaced due to differences in the disconnector timing with the M1911A1 slide- some of those M1911 frames had 2-digit serial numbers and really belonged in a museum.
We put two magazines of .22 long rifle through each after the pistols were bebuilt and refinished, and cleaned then of the sometimes years of lead buildup in the floating chambers, some of which were virtually soldered together; I wish I could sweat-solder that well when I'm trying to....
The property tag on one was signed out to a couple dozen midshipmen, including one Midshipman James E. Carter. I think that one found its way, complete with tag, to a museum as well. Those guns had seen some really hard use, but of some 1100 guns I think we only scrapped out a couple of dozen frames, replaced with NM M1911A1 frames easily enough. The .22s hadn't beaten them up too badly, but they sure leaded those barrels, some of which we melted out at 425º.
I've carried a Browning GP since 1967, the same one since 1969, with right close to 100,000 rounds through it and only minor replacements- the wooden grips split out at the screw holes and were replaced with green tape initially, a pair of L9A1 Austrailian Hi-power grips eventually. I still carry it sometimes, backed with a .45. Nice combo, and I can hit very well with the 9mm, thank you.
Note though, that the Marines are looking VERY hard at the long-barrelled version of the new H&K XM-8, and are considering a all-hands purchase.