Good point.
A general rule of thumb is that a buckshot load will spread about 1" per yard using a 12 gauge.
So in your RV the longest shot you might take would be no more than 5 yards.
This would result in a 5" pattern.
Choke size does not seem to matter much when using any sized buckshot.
This is no time to close your eyes and shoot in the general direction. You must aim.
Another thing worth noting is the the larger the shot size the the more energy retained, the deeper the penetration.
Buckshot will most certainly exit the wall of any RV and most homes.
Not disputing Dave's number, rather disputing the myth of the "no aim, just point and shoot scatter gun".
The "Newhall incident"
2 LEO's pull over 2 bad guys. While one LEO is searching the driver, the passenger exits the car. The 2nd LEO was carrying a 12 gauge Remington 870, loaded with buckshot and unfortunately at "port arms", and approaching the car from the rear, at the right rear quarter of the car. Port arms - one handed, butt stock on the hip, barrel facing up.
The bad guy exited the passenger seat and drew down on the officer so fast that the LEO did not have time to get his 870 in firing position, never firing a shot he suffered two 357 fatal wounds. Unfortunately the 1st LEO, in an attempt to defend his partner, lost track of the first perp and was gunned down at point blank range.
Next 2 LEO's on scene engaged the bad guys, one with a Remington 870. The LEO with the 870 fired the gun so fast he accidentally ejected a live round, and of all the rounds fired - ONE PELLET hit a bad guy in the forehead, and only inflicted a minor injury. I don't have a Remmy 870, but every pump I do have requires a distinct action to eject a live round, so I don't understand how this happened. Do 870's have a release tab in front of the trigger guard like many others?
In all, 4 CA Highway Patrol officers were gunned down. These were trained officers, 2 using 12 gauge shotguns, who between the two, only made one hit with one pellet.
The above incident completely changed firearm instructions for LEO's across the country. Not only was the training for shotguns insufficient, but in LA at the time, all officers trained with .38's but carried .357's. In the shootout, the LEO firing the revolver had no hits and was executed while trying to re-load, one shell at a time, as at the time, they were not issued speed loaders. It is believed his accuracy suffered due to training with light .38's and then firing the much heavier .357.
Point is, these were 4 well trained (at the time) young officers (23-24) who should have won the battle. How many civilians actually expend anywhere near the time and energy as LEO's training and actually firing their weapons? We are responsible for every round hit or miss.
BTW, this was the same incident in which a civilian happened upon the scene (former marine), picked up one of the discarded weapons and engaged the bad guys.
He also did not get any hits before running out of ammo. Luck was on his side though and he managed to avoid getting shot.
And remember - racking the slide of a pump shotgun only gives away your position.