Winchester 10MM Big Bore or 40S&W Imposter

Winchester Big Bore 10MM

10MM happens to be my favorite caliber and as of late it has been on a real resurgence, Just about every major pistol manufacturer has a 10MM pistol in their lineup. For someone like me this was great to see but not really proof it was back fully until ammunition started to show up on the shelves. Prior to the covid pandemic things were looking decent at just about every big box store.

We all know what happened during the pandemic. The world was shut down, the logistics chain struggled to match demand and all ammunition just about disappeared from shelves. In the 10MM fanatic circles we all questioned is this it would 10MM survive. As things started to look a little more on the positive side companies like Springfield armory would introduce it’s version of the XD in 10MM and then finally what we all had been asking for more than a decade. Smith and Wesson released it’s 10MM in the coveted M&P lineup.


Winchester Big Bore 10MM or Imposter

Us 10MM fans still weren’t as optimistic. 10MM was still being produced boutique like shops Buffalo Bore, Underwood, Fenix Ammunition and Doubletap. These shops rest assured are real 10MM shops as I have tested these brands across the chronograph and into ballistics gel.  Though it seems us 10MM fans can always count on these brands and they are often highly recommended. 10MM resurgence to me is not fully a success until it starts to show up on Big Box store shelfs from major manufacturers Like Federal, Winchester, Speer and others. So for me to see what almost looks like a new lineup from Winchester branded Big Bore generated real excitement for me. 


Could this be real? Not having heard of this left me with mixed emotions. Was this real 10MM or just a 40S&W Imposter posing as 10MM. Within minutes my mind was made up and I walked away leaving it on the shelf only to find myself standing back in front of the shelf after completing the rest of my shopping feeling as if I had let the 10MM community down by not even testing it. So then I pulled out my phone and pulled up Winchester website to see this new lineup was being produced in 10MM, 44Magnum more to come on this caliber later, 357Magnum and 45Colt. All of which according to Winchester produced some very impressive numbers.

muzzle 1175 613
50 1080 518
100 1011 454
175 934 387

Honestly this led to more questions. Could Winchester really live up to their ballistics claims and their marketing.

“Winchester Big Bore is trusted to perform in personal defense situations and hunting applications”

Deep Penetration
Semi-Jacketed Hollow Point Design controls and delays expansion.
Optimized Expansion
Achieves massive shock and produces lethal wound channels.
Reliable Performance
Dependable in critical personal defense and hunting situations”.

Pulling one of the freedom pills made me put this ammo back on the shelf as the hollow point didn’t look all that impressive by my untrained eye. 


I had very little hope for expansion as the cuts that form the hollow point seemed to be more like indentions or markings.


10MM Testing Must Go On

Ok yes as you can tell by the pictures above a box of it followed me home. I made the sacrifice in the name of testing for us 10MM fans. I must admit I was still very excited to see this ammo on the shelf much so that I was totally side tracked in getting my Saturday project done and headed right to the bench for a deeper inspection.


What do we have here?

Cartridge is from Ammo Manufacture: Winchester BIG BORE 200gr SJHP
Ballistics Information: 10mm Auto
Muzzle Velocity: 1175 fps
Muzzle Energy: 613 ft. lbs
Brass Make/Headstamp: Winchester – Brass
Bullet Make/Weight/Construction/Info; Length 0.6775/Dia. 0.4000:BIG BORE SJHP 200gr
Actual weight 200.2 grains   Crimp squeezed bullet to 0.3995
C.O.A.L.: 1.2505

Primer: brass color
Case: Diameter 0.4220 Crimp Diameter 0.4215 (Medium Length 0.9890)
Powder Description/Positive ID/Type/Charge ?? WAP ?  Weight: 7.9 ? 8.0 grains
?Winchester Action Pistol is Similar to Silhouette  (very fine flatten ball)?

If this truly is WAP powder I believe it is a little on the fast side to generate the velocities quoted. But you know what if nothing more this can lead to another FUN DAY on the Range Testing 10MM


Testing Results

Velocity out of the Colt Delta Elite Gen2 was about 100fps short of its advertising and penetration in the gel was inconclusive. The round exited the side of the second block after penetrating 19inches of gel which led me to believe there was probably little expansion. In the spirit of happy wife happy life I needed to get going to get myself back home to finish up that Saturday project that I had just blown off.


Accuracy was impressive but was only tested at 7 yards. Though not a surprise when you see how consistent this ammo was loaded with an extreme spread of 19 and standard deviation of 6.


I am not sure of the full claim of Winchester “For personal defense and hunting” Due to what seemed like a lack of expansion I personally would not use it as a self defense round in fear of over penetration. Though for exciting adrenalin pumping handgun hog hunting with shots kept to 40 yards or closer depending upon your capability to place a well aim shot this could be what you are looking for as it did produce 499ft/lbs of energy  with deep penetration. 

Part 2: Winchester & Kriss Vector Carbine