Went to the range yesterday with 3 boxes of WINCHESTER M-22 45gr ammo (all stamped with run number: 1LD21M).  About 15% of the rounds were duds.  Deep firing pin indentations in correct place on ammo but would not fire.  The almost new S&W M22 Victory pistol I used has fired over 200 rounds of other brands of 22LR with zero malfunctions and zero ammo problems.  The stamped run # is difficult to see on these boxes.  Look on backside of plastic box and reflect light off the box and the # will be visible.  Ammo is marketed as being more quiet than HV 22 ammo but it isn't.

In general, I've found M-22 to be bad/inconsistent regardless of lot.  I've shot about 1k rounds and had the same failure rate as you, and shooting it out of my 22 upper on my AR with suppressor attached it is obvious that this ammo is wildly inconsistent.

I've probably got about 2k rounds of it here I need to decide to try and shoot or just sell.

I'll agree, I snagged a 3xx count box of Winchester .22lr in the white box, and all of it was terrible. The crimps on a third or the rounds were so bad the slugs would spin freely. Even my trusty ol' Speedmaster wouldn't run it reliably. The only thing that would was my HK MP5-22, but once in 50 a case would stick in the chamber really bad, so I gave what was left away.

I like Winchester's Train & Defend 147 gr. 9mm, it's great ammo and reasonably priced. WWB .45acp isn't bad either if the price is right. But I've had some real junk in their .22lr, 9mm & shotgun ammo. Enough I don't buy it anymore. Al least the el cheapo Aguila & Perfecta and all that foreign steel stuff is reasonably consistent. Not sure who is stamping out Winchester's cheap stuff these days.

Me too. Bad luck with Winchester cheapest ammo of 22 and 45. 9 has been fine. However, I have yet to find any 9 ammo that my Glock will not shoot. Even the mighty Tula fires without issue. I no longer run out of ammo where I have to buy whatever is on the shelf, and ammo in general is readily available if you are out and about when you decide to go to a range with just your carry gun with you.

I think Winchester and Remington are in competition to see who can make the most craptacular 22lr ammo.  My recent experience with Super X indicates that Winchester is currently winning.  Wildly erratic report and POI, with some case failures.  No more for me.