Hopefully the image linked.
This is my current bushcraft and general hunting gun built on an H&R Handi-Rifle (SB2) receiver. H&R/NEF made two receivers, dimensionally identical. One was shotgun only (SB1 - cast iron) and the other was a rifle receiver (SB2 - steel).
This single shot break open firearm is simple and super reliable. It has a strong enough ejection that it will shoot an empty plastic hull back over your shoulder.
The top barrel is a 29.5" 12ga vent rib smoothbore with removable chokes.
The 24" barrel on the gun is a fully rifled 12ga barrel. It will drop a T-Rex, quickly, but you had better be in a manly mood when you shoot it, lest you shed a whimper and possibly some tears from the recoil. Being quite manly, I shall describe the recoil as 'brisk and refreshing'. Others, obviously not as manly as I, have described it in various terms such as 'brutal', 'inhumanly savage', and 'I now need a chiropractor'.
The fully rifled barrel gives a very good level of accuracy to .50cal sabots, 1oz pumpkin balls, and some other slugs like the 1oz and 7/8oz Lee 'keyed' wad slugs.
I have a 3rd barrel that is identical to the 24" fully rifled barrel, including similar adjustable sights, but it is smoothbore. Though intended to be a slug gun for deer hunting, I have had it tapped and threaded for removable chokes to increase it's versatility. The chokes on both smoothbore barrels are Winchester/Mossberg/Browning Invector compatible.
The black tubes are chokes, including a rifled choke for the smoothbore barrels. The smoothbore barrels already each wear a choke all of the time.
The silver tubes are sub-caliber adapters. The long one is a 7" (5" rifled) .22LR adapter. Below that are a 3" 20ga smoothbore, 3" .410/.45 Long Colt smoothbore, 3" .40S&W (rifled), 3" .38 Special (rifled), and 3" a .22LR (rifled). The fully rifled barrel can only use the shorter 3" adapters due to the rifling not allowing clearance.
The rifled adapters are legal here in Texas, but maybe not across the pond.
For things like shooting squirrels out of trees I can use a .22cal lead airgun pellet and a .22cal rimfire nail gun blank. You use a wood dowel ramrod to shove the pellet into the adapter's breach to where it contacts the rifling on the adapter. Insert the blank and you are good to go. This keeps me from launching a .22LR bullet onto a ballistic trajectory in case I miss (which might happen, occasionally , maybe, on every other full moon). This also works if there is a .22LR ammo shortage.