35 cal polymags - are they used much?

I used them in my Benjamin bulldog. They have less penetration than domes and open up nicely. I am not in the group of people that go along with knockdown power and I'm rarely worried about over penetration when using a big bore. That being said I saw the damage the polymags did and rather than a straight hole it did open up more. I can't really think of practical reason you would want that but I can say they do mushroom and do thier job. Maybe if you wanted to hit a pig in the head and not have an exit wound or something. Dead is dead tho and domes work fine. 
 
I use them all the time in my Bulldog! They have excellent stopping power!

https://youtu.be/4ft-YPQEcAs

https://youtu.be/aLXTueSqyOI

https://youtu.be/D6R-R2TsDWs

They are also my most accurate round out of my Bulldog. Look at this +100 yards headshot with the Polymags:

https://youtu.be/-4mo_p1tPXs

They have excellent temporary wound cavity performance in ballistic gel, and I'm certain that attributes to their ability to stop animals dead in their tracks.

VideoCapture_20211218-044628.1646471426.jpg

 
I use a variety of slugs and pellets in my Bulldog but find polymags perform really well. That being said roundball are very accurate in my rifle out to 35 yards or so and are super cheap to shoot. They're also deadly on small game. For medium game like coyote, big raccoons, etc... I like the polymags or the domes and for anything bigger I like the NSA 147 grn slugs.