My info is dated, though, as I haven't updated my training since S&W stopped servicing their SW99/990L series models, and I think my last Walther armorer manuals were received back about 2010 or 2011. Things like specifications, materials and manufacturing methods can change pretty rapidly, which is why most major gun companies to create armorer training programs like armorers to recertify every 3 or 4 years (varies).
Fortunately, I just have to keep my hand in the 99 series enough to inspect, service and repair my own older model 99's, and those of a close friend (another retired peace officer and former firearms instructor). I was able to order and put back enough parts to keep our guns running for hopefully the rest of our lives. That's no small task with him, as he shoots a couple of his (9/.40's) all the time on his own private rural range.
Last time I asked him about an approximate round count, while I was inspecting his 99's a couple of years ago, he told me that he'd probably fired another 15-20K rounds since my last inspection ... and back at that time he said he'd fired more than 65K through each of his full-size SW99's. It was during
that visit (bringing me several of his guns to inspect) that I'd initially thought he was screwing around me.
I usually suggest he clean his guns more frequently, as he typically brings them to me fouled from shooting them. (He usually says, "Hey, you're only to clean them anyway, right?") Anyway, that time, when I field-stripped his SW9940, I found it literally filled with oily and fouled sawdust, and not all little bits, but also including some sizeable damned chunks.
When I looked at him, he just shrugged and explained that he'd spent the last few days doing a lot of fence repair, using a chainsaw, and he'd not had time to clean the weapon. When my expression didn't change, he added that it wasn't a big deal, because he'd fired it on his range during and after the chain saw work, including right before he'd brought over to me, and it had functioned just fine. He didn't see the big deal. Well, hell, he did spend his formative young adult years on a couple of tours in SE Asia, after all, and has always had a different perspective regarding weapon cleanliness.
I gave him some more RSA's and told him to at least replace the springs a little more often ... and please keep the damned sawdust out of his weapons. Like that will do any good. It's almost always an adventure when he brings me his revolvers, 1911's and other pistols to me to inspect them.