[3.5] Free caster level increases on magic weapons?

[Mr Adventurer]

So I noticed this in the SRD:
Caster Level for Weapons
The caster level of a weapon with a special ability is given in the item description. For an item with only an enhancement bonus and no other abilities, the caster level is three times the enhancement bonus. If an item has both an enhancement bonus and a special ability, the higher of the two caster level requirements must be met.

However, special weapon properties have a fixed cost.

Does this mean I can buy a magic sword which is intelligent and can cast Haste on me, then enhance it to a +5 weapon to make its caster level 15 and thus the haste last longer and be more difficult to dispel?

[BowStreetRunner]

Does this mean I can buy a magic sword which is intelligent and can cast Haste on me, then enhance it to a +5 weapon to make its caster level 15 and thus the haste last longer and be more difficult to dispel?
The caster level of an effect is different from the casting ability of the item if it is intelligent. A +5 enhancement bonus is an effect as is the Vorpal special property. Having one of these on your weapon is going to make it a more powerful magic item and thus give it better item saving throws and such. That doesn't have anything to do with the item's own casting ability. Nor does it have anything to do with any effects that the item casts, such as with a spell storing weapon.

What you are suggesting would be akin to having a 20th level wizard cast a spell on a 5th level wizard and then stating that the 5th level wizard now has a caster level of 20.

[Mr Adventurer]

No, they're not really analogous. I take the point about intelligent item powers specifically, but the query still stands - for example, the Prismatic Burst power from the Magic Item Compendium has and requires a Caster Level of 13. If I put that on a +5 sword, which has a caster level of 15, does the Prismatic Spray effect which triggers on a critical have a CL of 15? This would be useful for overcoming SR.

[BowStreetRunner]

No, they're not really analogous. I take the point about intelligent item powers specifically, but the query still stands - for example, the Prismatic Burst power from the Magic Item Compendium has and requires a Caster Level of 13. If I put that on a +5 sword, which has a caster level of 15, does the Prismatic Spray effect which triggers on a critical have a CL of 15? This would be useful for overcoming SR.
No, it does not. Even though the sword uses the highest CL for things like saves and such, each effect still has its own CL. However, you can put an effect on with a higher CL than normal - either by crafting it yourself or by paying someone more for a more powerful version.

EDIT: For further clarification see Magic Item Compendium page 221 "The description of an item’s effect always supersedes the caster level given in the Caster Level entry. For example, even if an item with caster level 7th mimics a spell with a duration of 1 minute per caster level, if the item effect gives its duration as only 1 minute, you should ignore the normal duration in favor of this value."

[Solaris]

I know this isn't at all productive or contribute to the topic, but this thread led to the idea of picking up an intelligent magic item as a cohort for my wife's barbearian and having it pick up levels of bard.

A +whatever shocking thunderous greataxe, of course.

[Crake]

No, it does not. Even though the sword uses the highest CL for things like saves and such, each effect still has its own CL. However, you can put an effect on with a higher CL than normal - either by crafting it yourself or by paying someone more for a more powerful version.

EDIT: For further clarification see Magic Item Compendium page 221 "The description of an item’s effect always supersedes the caster level given in the Caster Level entry. For example, even if an item with caster level 7th mimics a spell with a duration of 1 minute per caster level, if the item effect gives its duration as only 1 minute, you should ignore the normal duration in favor of this value."

That's the item's ability superceding the normal effect. Which isn't really relevant. Since a magic item only has a single caster level, in the example given above with the prismatic burst, yes, it would overcome SR at CL 15, since the item is CL 15. It would also be harder to neutralize with a targetted dispel for the same reason.

This is generally the reason why many armor and weapon abilities have set limits, as BowStreetRunner described, so increasing the caster level won't increase the strength of the effects (which would need to come with a corresponding increased cost), just let them scale for certain things that come with just being higher level, such as dispelling and overcoming SR.

[Mr Adventurer]

That's the item's ability superceding the normal effect. Which isn't really relevant. Since a magic item only has a single caster level, in the example given above with the prismatic burst, yes, it would overcome SR at CL 15, since the item is CL 15. It would also be harder to neutralize with a targetted dispel for the same reason.

This is generally the reason why many armor and weapon abilities have set limits, as BowStreetRunner described, so increasing the caster level won't increase the strength of the effects (which would need to come with a corresponding increased cost), just let them scale for certain things that come with just being higher level, such as dispelling and overcoming SR.

Yes, this is what I'm saying.