I noticed the striker imprints on primers wasn't a deep as I recalled on a very early M&P9 so I decided to do the trigger return spring, recoil spring and striker assembly replacements. The suggested interval is 5 years/5,000 rounds.

The new trigger return spring was obviously stouter than the old, didn't try to establish weight differences, didn't think of it. The striker spring at rest (removed from striker assembly) was about 1 1/2 coils shorter than a new factory one. There was a marked difference in striker assembly tension on the end cap. If you're not changing entire striker assemblies, don't forget to change the striker return spring too.

The new recoil spring assembly was also noticeably stouter than the used one.

Trigger weight after change out is about 6 lbs & crisp. Or as crisp as a M&P 1.0 gets.

Something to bear in mind for those with time/round count on their own. That striker return spring could come back to bite you if ignored.

Crud & gunk getting into the striker channel is (usually) the culprit when it comes to strikers not striking as deep as usual (that is, unless you're shooting ammo with harder primers).

I've found that the usual culprit for crud & gunk getting into the striker channel is owners being sloppy with their cleaners and lubes when cleaning around the Striker hole.

I'm usually pretty cautious about cleaning the striker hole and when my Shield reached 20K rounds (I'm at around 25K now), I took the striker group out and ran a long Q-Tip down the channel. It was clean as a whistle.

I'm still using all the original Factory springs and it's still working fine.

When I talked to a CS rep a few yrs ago, they said they didn't really have a suggested time frame for swap-outs.
(at least, not for the Shield)

I got introduced to the M&P line as our service pistol when it first came out. The maintenance recommendation mentioned above was from the LE armorers school. Striker channel was clean, I had the parts, no point in letting them sit around. I had no malfunctions, prior to the change, just thought it was a good idea to do some preventive maintenance.

IIRC, they backed off the recommended change of extractor/extractor spring that went with the above. There's a margin note in the manual that the extractor doesn't need gauging as originally stated in the manual.

As we're currently getting 40 days & nights of rain in 24 hours, I haven't tested.

Just out of curiosity but where did you get that info from? I don't remember seeing this in my owners manual.

You wouldn't have found it in the manual. Read the post just above yours again. Also bear in mind ~$30-$35 in parts regarded as wear items, is insignificant compared to what you spent in ammo to get to that point. Also, there may have been changes to those recommendations in the last ten years, a couple from years back are noted in the post I just mentioned.

When the M&P9 first came out the late Todd Green did a 60,000 plus round test (in 171 days) and faithfully recorded results on the mp-pistol site and partially on his own website. I thought I had a summary of his stuff but can't find it. Might have been in some stuff I was unable to download before retirement.

RGV, I owe you a big one, I went and found incomplete notes on replacement intervals Todd determined by breakage. Based upon his tests he suggests changing out these parts at the following intervals: Mag catch, 12-13K rounds (there was a design change, this may not be current); recoil spring, 10K rounds; slide stop, 10-20K (go 20K) rounds and trigger return spring, 20K rounds. I apparently didn't write down the striker assembly interval. Gonna have to poke around some more, maybe hit the other website and see if I can find the striker interval.

The trigger return is a $3 part, but not fun to get to. After ten years, it didn't owe me anything. Recoil spring life of about 5K rounds about normal for any full size semi. Based on the difference in tension between the used & new striker springs, that would seem to be a prudent item to change also. You can't, at the moment, get the factory (5 lb) striker spring separately unless you're a certified S&W armorer. On the other hand, reduced power and 6 lb extra power striker springs are available aftermarket as are all the rest of the striker assembly parts. But, it's $8 for the striker spring & striker return spring, about another $4 for the plastic widget at the back of the striker, so changing the whole assembly is probably not that bad an idea. It's certainly easier.

And, after digging out some old cases, the firing pin indent may not have been changed. Oh well, needed doing anyway.

When my M&P 40c approached 10,000 rounds, I asked S&W customer service for a new striker assembly, and they promptly sent one free of charge. So it never hurts to ask. It's definitely a lot easier (and cheaper) than paying for parts and rebuilding it yourself.

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What, me worry?

Good to know, I didn't even think about that when I built my stash of wear parts. But I did that years ago. I kinda expect 10K rounds is an expected factory replacement interval-if they backed off that initial 5K suggestion.

I noticed in my last M&P pistol recert that the manual was now listing some recommended replacement intervals for some parts and assemblies.

FWIW, the trigger return spring and recoil spring assembly are a couple of the parts listed as recommended for replacement at every 5K rounds, and the Striker assembly is listed at every 10K rounds (along with the trigger bar assembly). There are quite a few parts and assemblies listed beginning at 20K rounds.

FWIW, there's an additional note added to the striker replacement recommendation of the 10K round service interval, which is to replace the assembly after 30K dry-fire cycles.

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Ret LE Firearms inst & armorer

OUTSTANDING! Thanks. Not to be nosy, but what's the interval on extractors/extractor springs if you recall?

BTW, for those who might be interested, after the parts replacements, the trigger is very slightly firmer and the resets are much more noticeable if that's a big item for you. I don't believe I ever noticed the reset except at the 25 yard line in qualification.

Sending you a PM.

BTW, the striker assembly replacement at 10K is only for the 9/.40 guns. The striker replacement for the .45 is listed at 20K rounds (or 30K dry-fire cycles).

The Shield has a striker replacement interval of every 10K for all calibers, or 30K dry-fire cycles.

The extractor and extractor spring aren't listed on the replacement interval list, at all. Just if repair is required. The extractors and their springs have reportedly been doing great.

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Ret LE Firearms inst & armorer