I'm getting ready for the summer backcountry season here in CO.
Up until this year I used a Sig SP2022 in 357sig in the back country. Since getting my P320 my SP2022 main stay has zero range time

and the P320 is what I'm going to be using in the backcountry. In a perfect world I would have a very nice 357mag, 44mag or 10mm, but thats not going to be happening any time soon.
My main concerns are running into unpleasant bipeds or the off chance of a quadruped. The chances of running into either are slim, but I would rather be safe
My bench mark for the round I would carry is the Speer 357mag
Velocity(in feet per second)
Muzzle
1450
50 yards
1261
100 yards
1118
Energy (in foot pounds)
Muzzle
584
50 yards
441
100 yards
347
I've settled on continuing to use 357sig and would pair with my P320 Carry setup. I may add a Springer 140mm or 170mm base plate to a Full Size mag for a few extra rounds. I like the 357sig round for many reasons including the bottle next design for reliable feeding and the ballistics. I'm only looking at solid non expanding rounds (FMJ or similar).
Underwood is currently what I'm leaning towards. They have a very nice selection of options. I'm currently leaning towards the basic FMJ.
They also have some interesting lighter weight bullets using flutes. The lighter weight fluted bullets would have no issue with a biped, but I wonder how effective they would be with a quadruped.
Here are some examples:
https://underwoodammo.com/product-category/handgun-ammo/357-sig/
357 Sig 125 Grain Full Metal Jacket Box of 50
- Muzzle Velocity:1475 fps
- Muzzle Energy: 604 ft. lbs
357 Sig 115 Grain Xtreme Penetrator
- Muzzle Velocity:1450 fps
- Muzzle Energy: 537 ft. lbs
357 Sig 90 Grain Xtreme Defender
- Muzzle Velocity: 1700 fps
- Muzzle Energy: 578 ft. lbs.
- Penetration: 17.5 inches
357 Sig 65 Grain Xtreme Defender
- Muzzle Velocity: 2100 fps
- Muzzle Energy: 636 ft. lbs.
- Penetration: 17.5 inches
I'm sure people have thoughts

, but I would also like to hear if people have used Underwood in the P320 and how it worked.