I doubt that either the 1861 Springfield or Brown Bess were every being fired at those speeds (the Brown Bess especially, the way those were actually loaded in fired in practice was VERY different than the ideal method to load for optimum range*), and you're forgetting a critical point: the weight of the weapon itself reduces recoil. After all, for recoil to happen you have to overcome the rest energy of the weapon itself, and a heavier weapon has more rest energy. As such, the fact that the Brown Bess and Springfield can both generate similar force is meaningless as they are both heavier than the M-Henry and thus similar force ends up generating less recoil since the gun itself absorbs more.
---------------
* To explain, for the pre-mineball muzzleloaders you had a fairly complex process to prep to fire. With an unloaded weapon the ideal method was as follows:
- Pour the powder down the barrel.
- Mount the bullet in wadding.
- Ram bullet down the barrel until its set on the powder.
- Tamp the bullet to ensure a good set.
- Prime the weapon.
- Aim
- Fire.
However, this is a LONG process and is not actually required for muskets. You could cut out Steps 2 and 4 from this process for muskets and still successfully fire. However, this meant that the explosion is not going to be as tightly contained (since there's not firm wadding containing the explosion) nor is the powder burning as uniformly (since you didn't tamp it down). Thus lowering the muzzle velocity of the round (and also making it less accurate), however, cutting those steps is how you could get up to the three rounds per minute that the Redcoats were famous for with the Brown Bess. Meanwhile, going through each of these steps is REQUIRED for rifles which is why they were so much more slower firing, but also why they ended up much more ACCURATE (along with the rifle grooves, obviously).