I actually like the DMG stats and they make more sense for slightly later firearms (i.e. reloading a musket in 6 seconds seems really hard).
But since you asked, I think the stats you posted in your first post are pretty good. Those damage numbers seem about right; slightly better than a crossbow, but only slightly. The 2d4/2d6/2d8 stats seem overpowered to me; you don't want guns outclassing melee weapons unless you expect people to just stop using melee weapons (which changes the tactical game considerably). Now 2d4/2d6/2d8 might be balanced if those weapons take an action to reload, or have some other onerous requirement.
The blunderbuss spread rules are a little confusing. You could try phrasing the area as a line, 5-feet wide up to short range and then 10-feet wide up to long range; that seems a little clearer than what you have written.
I actually don't know much about the blunderbuss, but if it's anything like a modern shotgun, I think the spread effect is often greatly overestimated. The spread makes it more to hit, but catching multiple enemies in the blast is rare. I might do something like: range 30/120, damage 1d10/1d6, +2 to hit. The flat +2 bonus is less powerful than advantage and interacts better with the range-increment rules. The damage step-down is a bit more extreme, too, to make up for the better range. The only downside to doing it this way is you lose the option to "accidentally" catch your allies in the blast. ;}
But since you asked, I think the stats you posted in your first post are pretty good. Those damage numbers seem about right; slightly better than a crossbow, but only slightly. The 2d4/2d6/2d8 stats seem overpowered to me; you don't want guns outclassing melee weapons unless you expect people to just stop using melee weapons (which changes the tactical game considerably). Now 2d4/2d6/2d8 might be balanced if those weapons take an action to reload, or have some other onerous requirement.
The blunderbuss spread rules are a little confusing. You could try phrasing the area as a line, 5-feet wide up to short range and then 10-feet wide up to long range; that seems a little clearer than what you have written.
I actually don't know much about the blunderbuss, but if it's anything like a modern shotgun, I think the spread effect is often greatly overestimated. The spread makes it more to hit, but catching multiple enemies in the blast is rare. I might do something like: range 30/120, damage 1d10/1d6, +2 to hit. The flat +2 bonus is less powerful than advantage and interacts better with the range-increment rules. The damage step-down is a bit more extreme, too, to make up for the better range. The only downside to doing it this way is you lose the option to "accidentally" catch your allies in the blast. ;}