@The Eric,
I did a little digging, Winchester does use a specific primer called a 116M-282A. I have never heard of it. I don't believe it is available to the public for reloading or I would have seen it before. It seems as Winchester forgot to designate the primer, but the 1 1/2 is SP, the 6 1/2 is SR, the 116 is SR, the 116M-282A does not list SP or SR, but since it is designated as 116M, I would say it is a SRM, Small Rifle Magnum, but Winchester does not make a SRMag primer available to the public except for the Nato Spec #41 which they only started making 7/8 years ago.. The other that I separated is the Nato spec #41 that is used in all 5.56 ammo to prevent slam fire, it is a SRM also, but with an even harder cup.
I would take a wild guess and say the 116M primer is as another member posted, Nato spec to prevent slam fire in some type of full auto 9mm rifle/pistol. I believe they are harder than the regular SR primers.
I would suggest exactly the direction you have chose, the striker replacement since Sig has acknowledged that it's a problem on some of their early 365 pistols, and by the looks of the skid marks it has left on your primers.
Winchester Nato, and All Nato headstamp brass cartridges have crimped primers, from the pictures you have posted, some of those WW cases look pretty nasty in the primer cup area. Fiocchi is another ammo brand that is in the same price range for plinking ammo, and is very good quality.
"Straight from Winchesters website"
Prepared to U.S. OSHA, CMA, ANSI, Canadian WHMIS, Australian WorkSafe, Japanese Standard JIS Z 7250:2000, and EU REACH Regulations 1.
PRODUCT AND COMPANY IDENTIFICATION Product Name: CAS Number: Synonyms: Product Use: U.N. Number: U.N. Dangerous Goods Class Manufacturer/Responsible Party: Manufacturers’ Address: Emergency Telephone Number:
SDS Control Group: Olin SDS No.: 00060.0001 Revision Date: 02/28/2019 Revision No.: 5 PRIMERS – CENTERFIRE Mixture – Metal Alloy
#1 ½, 108, WSP,
#1 ½ M, 108H, WSPM,
#6 ½, 116,WSR,
***116M-282A,***
#7, 111, WLP,
#8 ½, 120, WLR,
#8 ½ M, 120H,WLRM,
#34 Primer,
***#41 Primer,***
50 Cal Primer,
M29A1C Primer,
M35C Primer,
M42C1 Primer.