Different guns............
Over the years, I've carried a buncha different Truck/Trunk guns.
And, they varied. But, they were about All, Old Beaters.
I've had an old Marlin .22 auto-loader, an SKS, a single brrl. 12 ga.,
a bolt-action 20 ga. Mossberg, and a beat up Savage 12.ga. pump.
Prob'ly been a couple more.
I have never had a "new" Truck/Trunk Gun.
I think the most I paid for one was about $150 or $175.
I traded for a couple of them.
I have carried a sidearm for many years also, all day, every day.
You gotta remember, though.........It is gonna get knocked around.
It'll get nicked up some.
It might get a little damp, or draw moisture when the weather changes.
So, it might pick up some rust.
Suit y'urself. But I would Not go with a pistol caliber Truck/Trunk Gun.
Shotgun or Rifle caliber would be best, AISI.
It's pro'bly just going to be what you might need, "in a pinch".
If you're already carrying a sidearm, you'll prob'ly never need a
Truck/Trunk Gun.
But, you can't have too many guns, right.
Have Fun.