pawsplay
Hero
The traditional D&D setting resembles the cusp of the high Medieval period and the early Renaissance, and thus I am comfortable saying it can go either way. Certainly cannons should be present in any D&D setting advanced enough to have articulated plate armor unless you deliberately choose anachronism.
LOTR is more similar to the so-called "Dark Ages," the early period of the Crusades, and hence has neither extensive gunpowder nor articulated plate armor, and crossbows are rare.
From a reality standpoint, a musket is in no danger of supplanting a longbow in effectiveness well into the 18th century. Despite good penetration, muskets are frankly slow, inaccurage, and have a fairly short effective range compared to the longbow (although it is possible, in theory, to make longer distance sniping shots with a well-tuned musket). Ben Franklin actually wanted to base the Revolutionary army on a longbow corps, but it was deemed impractical to acqurie so many longbows, or enough hired longbowmen to build effective fighting units particularly if it involved hiring many mercenaries. Guns don't overtake muskets in effectiveness until the late 18th and even early 19th century; the rise of gun warfare during the imperial era of US history had more to do with training issues and availability of bows than with the guns actually being more deadly. The Plains Indians did embrace firearms until the availability of rifling; prior to that, many battles were fought successfully using mostly traditional Amerindian bow and arrows.
So... unless you are planning on introducing rifling, or the Gatling gun, or you are making the breastplate omnipresent, there is no really good in-game reason why muskets should have superior combat abilities in D&D, even in a milieu that resembles a later era.
LOTR is more similar to the so-called "Dark Ages," the early period of the Crusades, and hence has neither extensive gunpowder nor articulated plate armor, and crossbows are rare.
From a reality standpoint, a musket is in no danger of supplanting a longbow in effectiveness well into the 18th century. Despite good penetration, muskets are frankly slow, inaccurage, and have a fairly short effective range compared to the longbow (although it is possible, in theory, to make longer distance sniping shots with a well-tuned musket). Ben Franklin actually wanted to base the Revolutionary army on a longbow corps, but it was deemed impractical to acqurie so many longbows, or enough hired longbowmen to build effective fighting units particularly if it involved hiring many mercenaries. Guns don't overtake muskets in effectiveness until the late 18th and even early 19th century; the rise of gun warfare during the imperial era of US history had more to do with training issues and availability of bows than with the guns actually being more deadly. The Plains Indians did embrace firearms until the availability of rifling; prior to that, many battles were fought successfully using mostly traditional Amerindian bow and arrows.
So... unless you are planning on introducing rifling, or the Gatling gun, or you are making the breastplate omnipresent, there is no really good in-game reason why muskets should have superior combat abilities in D&D, even in a milieu that resembles a later era.