When muskets were first adopted, armour was common on battlefields. In many parts of Europe, they main weapon they replaced was the crossbow. Why was the musket better than the crossbow? Three major reasons were:

• The musket had better anti-armour performance than even very powerful crossbows.

• The musket was cheaper than powerful crossbows.

• The musket was less delicate, and less susceptible to damage on the battlefield, damage from weather, etc. than crossbows.

Unlike the comparison with conventional bows (longbows and composite reflex-recurve bows), where the bow offered a superior rate of fire, but demanded much more training for effective use, crossbows and muskets offered similar ease of use (and thus similar levels of training for effective use), and similar rates of fire. Cheaper and better anti-armour performance made a big difference. It is also sometimes claimed that the musket also offers higher lethality, that musket balls are more likely to kill or incapacitate than crossbow bolts (or arrows). I don't know if there is good evidence for this, but it is plausible.

With the advantages of the musket over the crossbow, the adoption of the musket, replacing the crossbow, makes a lot of sense. Since the crossbow doesn't offer any significant military advantage over the musket, there isn't any good reason to keep using them alongside muskets. Retention of the crossbow would complicate logistics (e.g., more kinds of ammunition would need to be supplied).

However, the above applies to powerful crossbows that were designed to challenge armour. Less powerful crossbows can be (and were) made, able to be spanned (i.e., the string drawn back into place) by placing the foot in a stirrup and simply pulling the string back with both hands. Such crossbows offer a higher rate of fire, and are cheaper. With a simple wooden prod, they could be cheaper than muskets. Their performance against armour was poor - they were, essentially, incapable of penetrating any armour to be found on the battlefield. Would they have been a viable weapon to reintroduce once armour disappeared from the battlefield in response to the adoption of guns? The two main factors to consider are rate of fire and range.

• Rate of fire for hand-spanned crossbow vs musket: approximately 10-15 seconds vs 20-30 seconds. The crossbow has an advantage.

• Range: the musket certainly has a huge advantage in maximum range, and probably an advantage in effective range. Low powered Chinese crossbow are described as having effective ranges from 20m to about 75m. The later muzzle-loading muskets used on the battlefield had effective ranges of 150-200m.

• Lethality and performance against heavy clothing: clear advantage to the musket.

No great advantage would seem to be gained by switching from muskets to crossbows. Note that by the time armour disappeared as a factor on the battlefield, guns had improved from the earlier versions that had replaced crossbows in the first place.