EDIT: Answer completely re-worked on June 5; some comments may no longer apply.

This comes down to two issues.

##Issue One# What actually causes the detonation? The magic item says the beads detonate when exposed to magical fire or "when thrown". What is it about being thrown that allows them to detonate? Most likely the impact is the trigger that causes detonation once the beads are armed. The question is, what arms the beads?

Do they have to be primed somehow (like pulling the pin from a grenade), and if so how is that done (is simply detaching it from the necklace enough)? Do the beads somehow telepathically read the carrier's intent, so that they can distinguish being deliberately thrown from being accidentally dropped? Are they activated by reaching a certain velocity? Or are they always armed, and any impact above a certain threshold causes them to detonate?

If it's always armed or has to be primed before it's rammed down the barrel, then the blast from the black powder will almost certainly set it off (thanks Pulsehead for pointing out that it could be carefully rammed down the barrel without setting it off). If it's activated by the user's intent, then it can't be used with a firearm at all, since it won't detect that it's being thrown.

If, however, it's armed by reaching a certain velocity then triggered by impact, then you can probably use it in a firearm without any real risk of it detonating before it reaches a target after being fired.

As for once it's fired, if it strikes a target it should probably detonate immediately; the beads are intended to explode just from being thrown, so the impact of striking a target at firearm velocities should set it off instantly, rather than giving it time to penetrate. If it explodes from colliding with the target, there's not much the target can do to avoid the blast, so the target shouldn't receive a reflex save. Since the bead is being fired from a weapon, however, the attacker should have to make a typical attack with the firearm to actually strike the target.

#Issue Two# Does the DM want magic and technology to be combined like this? While it can allow a lot of interesting creativity (such as firing fireball beads from a musket), it also probably opens the door to a lot of potentially game-breaking combos. Magic and technology together are likely to be a "the whole is greater than the sum of the parts" kind of thing. You might even take the route used in the Amethyst setting and say that proximity to magic actually prevents technology from working.

EDIT: Answer completely re-worked on June 5; some comments may no longer apply.

This comes down to two issues.

Issue One

What actually causes the detonation? The magic item says the beads detonate when exposed to magical fire or "when thrown". What is it about being thrown that allows them to detonate? Most likely the impact is the trigger that causes detonation once the beads are armed. The question is, what arms the beads?

Do they have to be primed somehow (like pulling the pin from a grenade), and if so how is that done (is simply detaching it from the necklace enough)? Do the beads somehow telepathically read the carrier's intent, so that they can distinguish being deliberately thrown from being accidentally dropped? Are they activated by reaching a certain velocity? Or are they always armed, and any impact above a certain threshold causes them to detonate?

If it's always armed or has to be primed before it's rammed down the barrel, then the blast from the black powder will almost certainly set it off (thanks Pulsehead for pointing out that it could be carefully rammed down the barrel without setting it off). If it's activated by the user's intent, then it can't be used with a firearm at all, since it won't detect that it's being thrown.

If, however, it's armed by reaching a certain velocity then triggered by impact, then you can probably use it in a firearm without any real risk of it detonating before it reaches a target after being fired.

As for once it's fired, if it strikes a target it should probably detonate immediately; the beads are intended to explode just from being thrown, so the impact of striking a target at firearm velocities should set it off instantly, rather than giving it time to penetrate. If it explodes from colliding with the target, there's not much the target can do to avoid the blast, so the target shouldn't receive a reflex save. Since the bead is being fired from a weapon, however, the attacker should have to make a typical attack with the firearm to actually strike the target.

Issue Two

Does the DM want magic and technology to be combined like this? While it can allow a lot of interesting creativity (such as firing fireball beads from a musket), it also probably opens the door to a lot of potentially game-breaking combos. Magic and technology together are likely to be a "the whole is greater than the sum of the parts" kind of thing. You might even take the route used in the Amethyst setting and say that proximity to magic actually prevents technology from working.

EDIT: Answer completely re-worked on June 5; some comments may no longer apply.

This comes down to two issues.

Issue One: What actually causes the detonation? The magic item says the beads detonate when exposed to magical fire or "when thrown". What is it about being thrown that allows them to detonate? Most likely the impact is the trigger that causes detonation once the beads are armed. The question is, what arms the beads?

Do they have to be primed somehow (like pulling the pin from a grenade), and if so how is that done (is simply detaching it from the necklace enough)? Do the beads somehow telepathically read the carrier's intent, so that they can distinguish being deliberately thrown from being accidentally dropped? Are they activated by reaching a certain velocity? Or are they always armed, and any impact above a certain threshold causes them to detonate?

If it's always armed or has to be primed before it's rammed down the barrel, then the blast from the black powder will almost certainly set it off (thanks Pulsehead for pointing out that it could be carefully rammed down the barrel without setting it off). If it's activated by the user's intent, then it can't be used with a firearm at all, since it won't detect that it's being thrown.

If, however, it's armed by reaching a certain velocity then triggered by impact, then you can probably use it in a firearm without any real risk of it detonating before it reaches a target after being fired.

As for once it's fired, if it strikes a target it should probably detonate immediately; the beads are intended to explode just from being thrown, so the impact of striking a target at firearm velocities should set it off instantly, rather than giving it time to penetrate. If it explodes from colliding with the target, there's not much the target can do to avoid the blast, so the target shouldn't receive a reflex save. Since the bead is being fired from a weapon, however, the attacker should have to make a typical attack with the firearm to actually strike the target.

Issue Two: Does the DM want magic and technology to be combined like this? While it can allow a lot of interesting creativity (such as firing fireball beads from a musket), it also probably opens the door to a lot of potentially game-breaking combos. Magic and technology together are likely to be a "the whole is greater than the sum of the parts" kind of thing. You might even take the route used in the Amethyst setting and say that proximity to magic actually prevents technology from working.

EDIT: Answer completely re-worked on June 5; some comments may no longer apply.

This comes down to two issues.

##Issue One# What actually causes the detonation? The magic item says the beads detonate when exposed to magical fire or "when thrown". What is it about being thrown that allows them to detonate? Most likely the impact is the trigger that causes detonation once the beads are armed. The question is, what arms the beads?

Do they have to be primed somehow (like pulling the pin from a grenade), and if so how is that done (is simply detaching it from the necklace enough)? Do the beads somehow telepathically read the carrier's intent, so that they can distinguish being deliberately thrown from being accidentally dropped? Are they activated by reaching a certain velocity? Or are they always armed, and any impact above a certain threshold causes them to detonate?

If it's always armed or has to be primed before it's rammed down the barrel, then the blast from the black powder will almost certainly set it off (thanks Pulsehead for pointing out that it could be carefully rammed down the barrel without setting it off). If it's activated by the user's intent, then it can't be used with a firearm at all, since it won't detect that it's being thrown.

If, however, it's armed by reaching a certain velocity then triggered by impact, then you can probably use it in a firearm without any real risk of it detonating before it reaches a target after being fired.

As for once it's fired, if it strikes a target it should probably detonate immediately; the beads are intended to explode just from being thrown, so the impact of striking a target at firearm velocities should set it off instantly, rather than giving it time to penetrate. If it explodes from colliding with the target, there's not much the target can do to avoid the blast, so the target shouldn't receive a reflex save. Since the bead is being fired from a weapon, however, the attacker should have to make a typical attack with the firearm to actually strike the target.

#Issue Two# Does the DM want magic and technology to be combined like this? While it can allow a lot of interesting creativity (such as firing fireball beads from a musket), it also probably opens the door to a lot of potentially game-breaking combos. Magic and technology together are likely to be a "the whole is greater than the sum of the parts" kind of thing. You might even take the route used in the Amethyst setting and say that proximity to magic actually prevents technology from working.

To a certain extent it's up to DM fiat how sensitive the beads are. Any firearm that would use it would be a muzzle-loader (non-cannon breech-loaders almost universally used modern shape bullets rather than balls), which means it has to be rammed down the length of the barrel, a somewhat dangerous proposition. Probably the bead should need to roll fortitude (not reflex; the bead isn't dodging anything), or the person loading it should roll something appropriate (reflex? disable device to reflect the delicate nature of the task?), to determine whether the bead detonates while being loaded. The DC is going to be up to the DM, based on viable a strategy they want this to be.

As for once it's fired, if it strikes a target it should probably detonate immediately; the beads are intended to explode just from being thrown, so the impact of striking a target at firearm velocities should set it off instantly, rather than giving it time to penetrate. If it explodes from colliding with the target, there's not much the target can do to avoid the blast, so the target shouldn't receive a reflex save. Since the bead is being fired from a weapon, however, the attacker should have to make a typical attack with the firearm to actually strike the target. A critical failure on the attack roll would probably represent the bead detonating in the chamber when the weapon is fired.

EDIT: Answer completely re-worked on June 5; some comments may no longer apply.

This comes down to two issues.

Issue One: What actually causes the detonation? The magic item says the beads detonate when exposed to magical fire or "when thrown". What is it about being thrown that allows them to detonate? Most likely the impact is the trigger that causes detonation once the beads are armed. The question is, what arms the beads?

Do they have to be primed somehow (like pulling the pin from a grenade), and if so how is that done (is simply detaching it from the necklace enough)? Do the beads somehow telepathically read the carrier's intent, so that they can distinguish being deliberately thrown from being accidentally dropped? Are they activated by reaching a certain velocity? Or are they always armed, and any impact above a certain threshold causes them to detonate?

If it's always armed or has to be primed before it's rammed down the barrel, then the blast from the black powder will almost certainly set it off (thanks Pulsehead for pointing out that it could be carefully rammed down the barrel without setting it off). If it's activated by the user's intent, then it can't be used with a firearm at all, since it won't detect that it's being thrown.

If, however, it's armed by reaching a certain velocity then triggered by impact, then you can probably use it in a firearm without any real risk of it detonating before it reaches a target after being fired.

As for once it's fired, if it strikes a target it should probably detonate immediately; the beads are intended to explode just from being thrown, so the impact of striking a target at firearm velocities should set it off instantly, rather than giving it time to penetrate. If it explodes from colliding with the target, there's not much the target can do to avoid the blast, so the target shouldn't receive a reflex save. Since the bead is being fired from a weapon, however, the attacker should have to make a typical attack with the firearm to actually strike the target.

Issue Two: Does the DM want magic and technology to be combined like this? While it can allow a lot of interesting creativity (such as firing fireball beads from a musket), it also probably opens the door to a lot of potentially game-breaking combos. Magic and technology together are likely to be a "the whole is greater than the sum of the parts" kind of thing. You might even take the route used in the Amethyst setting and say that proximity to magic actually prevents technology from working.