Does firing a crossbow wielded in two hands prevent gaining a buckler's AC bonus?

Question

The description of the buckler (Player's Handbook 123, 124) (15 gp; 5 lbs.), in part, says

You can use a bow or crossbow without penalty while carrying [the buckler. I]f you use a weapon in your off hand, you don’t get the buckler’s AC bonus for the rest of the round. (124)

When a creature that's bearing a buckler makes one or more attacks with a light, heavy, or great crossbow that's wielded in two hands, does the creature lose the buckler's shield bonus to AC until the same initiative count on the next round?

Note that an answer may need to address the technical classification of crossbows as ranged weapons—and maybe even specifically as projectile weapons—rather than just treating them like melee weapons that fall into the usual categories of light, 1-handed, and 2-handed weapons.

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Note: Avery Clamp is an artificer/crossbowman who wields a great crossbow on his turn but snaps it into his glove of the master strategist at his turn's end. (It's safer there—folks have to ready an action to make sunder attempts against his great crossbow. It's also really heavy!) Although he carries a buckler mainly for its additional abilities, Clamp would still like the shield bonus to AC from his +1 death ward durable wand chamber buckler after making his great crossbow attacks.

Answer 1

RAW, no, but this probably isn’t a useful answer.

[I]f you use a weapon in your off hand,

This condition cannot be met unless you use the two-weapon fighting combat option, because you don’t even have anything known as an “off hand” to use for a weapon. That means two-handed weapons, and bows and crossbows used in two hands whether they are “two-handed weapons” or not, cannot trigger this effect and cost you your shield bonus to AC.

This seems pretty obviously unintended in my opinion, though—they explicitly refer to “using your off hand to help wield a two-handed weapon,” which RAW is literally impossible, and so not what they meant. They probably just missed this when they removed handedness rules in the 3.5e revision. What they probably meant was “in the hand attached to the arm that’s got the buckler strapped to it,” (since D&D apparently doesn’t know what a buckler is)—which, for that matter, could just as easily be one’s main hand. And for that, I would say yes, you are using that hand for a bow or crossbow, since after all you are holding the bow or crossbow up to aim, not moving that arm to deflect blows.

Answer 2

As you mentioned, the rules for bucklers state:

You can use a bow or crossbow without penalty while carrying [a buckler].

The rules then continue to define a two special penalties that can be accrued if using a buckler with other weapons. These penalties include:

• -1 penalty to attacks with weapons held in your off-hand
• loss of shield bonus at armor class after attacking with a weapon in your off-hand

All bows and crossbows are explicitly exempt from these penalties.

Note that you cannot attempt to use weapons with any other shield types. Ergo, these are the only penalties that exist for this situation. It is entirely unambiguous.

The full text for buckler rules, broken down point-by-explicit-line:

This small metal shield is worn strapped to your forearm.

Establishes what it is

You can use a bow or crossbow without penalty while carrying it.

Explicitly establishes that you can use a bow or crossbow without penalty while carrying a buckler

You can also use your shield arm to wield a weapon (whether you are using an off-hand weapon or using your off hand to help wield a two-handed weapon),

Establishes that the shield arm of the buckler may be used to hold a weapon in the off-hand or to help hold a 2-handed weapon

but you take a -1 penalty on attack rolls while doing so. This penalty stacks with those that may apply for fighting with your off hand and for fighting with two weapons.

Establishes a penalty -1 to attack rolls if wielding a weapon or helping hold a 2-handed weapon

In any case, if you use a weapon in your off hand, you don’t get the buckler’s AC bonus for the rest of the round.

Establishes that using an off-hand or two-handed weapon in your off hand denies your buckler's shield bonus to AC for the rest of the round, which is a second penalty. The language, "In any case," refers directly to "with those that may apply for fighting with your offhand and for fighting with two weapons." If you believe that this is not a penalty, then it will apply to crossbows, but in the rest of the game, being denied an AC bonus is a penalty in-line with other penalties for various actions.

You can’t bash someone with a buckler.

It would be embarrassing to try