I've got over 5000 round through my M&P22 and it has always been finnicky.  Unless I clean it every 100-150 rounds or so I get multiple FTF's to the point where I have to rack the slide after every shot.

I was out shooting it today in 25 degree weather and the damn would barely work at all.  I cleaned it and it shot OK for a while then started with the FTF's again.

This is shooting decent ammo no Golden Bullet.  It won't eat that at all.

So did I get a lemon or what?

Be happy it works clean with some ammo.  I am sure Umarex did the best they could converting something from their air soft and BB gun product line into a .22 for S&W.

Just be happy it is not a total POS like the SIG Mosquito was and probably still is.

Uh, I think Walther makes the M&P22, not Umarex. BTW, mine runs great but likes round nose ammo. CCI AR Tactical or Mini Mags are without a doubt the best ammo for the M&P22 (and M&P15/22).

mine runs like a champ, hasnt choked on any of the ammo ive ran, suppressed or not, it just keeps on going

I think I have about 8-10k through this one.  I soak it with rem oil before I shoot.  No issues then if I clean it then take it out dry I get problems on occasion.  I shoot almost entirely elly sport through it.

Honestly, you will get a better answer over here IMHO
I'm a member there too.
Any of the ammo called out in this http://www.smith-wesson.com/wcsstore/SmWesson2/upload/other/S&W_M&P_1522_Rifle_Manual.pdf

EDIT-misread, thought your were asking about the rifle version, still the forums have hand guns too. My bad.

No. I have seven mags total and it happens with all of them.

Yep.  I also polished the feed ramp.  It almost seems to have a sticky slide.  It just doesn't slide smoothly once it gets a little dirty.

Does anyone make extra power recoil springs for these?  I'm probably just pissing into the wind but it's worth a shot.

"In June of 2012, Arnsberg, Germany based PW Group, owners of shooting sports companies, CARL WALTHER Sportwaffen and UMAREX Sportwaffen, announced the formation of Walther Arms, Inc. to handle all the importation, sales, marketing, distribution, and servicing of Walther products in the United States early in 2012. The transition occurred in two phases in 2013. Previously, Smith & Wesson held responsibility for the distribution of Walther firearms and accessories in the United States. On January 1, 2013, that responsibility was transferred to the newly formed Walther Arms, Inc.

Walther and Smith & Wesson will maintain their strategic alliance on several fronts—Smith & Wesson will continue to manufacture the PPK for Walther Arms, Inc. and CARL WALTHER will continue to manufacture the M&P22 handgun for S&W. Additionally, UMAREX will continue to license the Smith & Wesson brand for airgun products.

We are extremely thankful for the relationship we have had and will continue to have with the quality organization of Smith & Wesson.  Smith & Wesson has been an outstanding partner and has represented the Walther brand in the U.S. with tremendous focus, effort, and results. We look forward to many more years of strategic alliance with Smith & Wesson.

Walther Arms, Inc. will begin operations sharing a corporate campus in Fort Smith, Arkansas with Umarex USA, another company in the PW Group. Adam J. Blalock has been named President & CEO of Walther Arms, Inc. and will also remain as President & CEO of Umarex USA. “We are grateful for the way Smith & Wesson has represented Walther and we look forward to our continued relationship with them”, said Blalock, “We will have a dedicated team focused on meeting the needs of U.S. consumers with high quality, innovative products worthy of the Walther brand. We are very thankful for the many loyal Walther customers and we’re excited for the opportunity to serve them.”

 Walther is known throughout the world as a leader in handgun innovation and quality. The new U.S. based Walther Arms allows a more direct influence from the U.S. consumer’s wants and needs into our product development."

From the Walther Website.  Other "branded" similiar items are made by Umarex, marketed by Walther, and distributed in the US by either the major brand or by Walther via PW.

My scapel does not cut apart German companies to show any more layers of who does what.  When something is made with the same materials and to the same poor quality as BB guns and airsoft guns, I figure Umarex did it.  Slide logo not withstanding.

Try using spray silicone lubricant.

I have a pair of those S&W "medium" black CO2 air pistols.  They are the finest air gun pistols I've ever used and very much like a real M&P.  I liked them so much, I bought the centerfire M&P.  When all else fails, I got holsters that fit and there is worse draw and fire practice than using those CO2 guns.  I just wish they would make a Shield like that in BB.

Oddly enough, both of them shot a mile high when they were obtained.  I milled down the rear sights for a 15 yard zero and could not be happier with them.

There isn't really any quality control at Umarex though.  One of them could not be fired when it was new without about a 12 pound pull.  The trigger ran into the bottom rear of the trigger guard before it went far enough to the rear to release the barrel for its backwards firing stroke.  You really had to muscle it to fire it.  

Midway wouldn't take it back because I had changed the rear sight and Umarex would have made me pay two way shipping on a $34 air pistol.  I used a Dremel and reshaped the rear bottom inside of the trigger guard so the trigger could pull through without bottoming out on the frame.  Works perfectly.  1/2 hour careful Dremel was better than shipping two ways.  One cylinder lasts about 5 magazines.  

Some of the other pistol copies are terrible, especially the Walther BB gun, but the M&Ps are great,

Hmmmm.

No wonder, it's a BB gun.

I was being sarcastic.  I know that is difficult to discern when reading.  We need a sarcasm emoticon.