Full round casting ala sorceror using metamagic

[Adaff]

I'm currently playing with my home group. They all disagree with me that casting a metamagic spell as a sorcerer happened on the beginning of there next turn.
As its a full round action it would only take up a standard and move.

I was under the assumption that it finishes casting and the effects begin on the next turn. Here's the full text. Am I wrong? Could some only clarify the rules, there is some weird wording. Especially considering the difference between 1 round casting time.

Cast a Spell

A spell that takes one round to cast is a full-round action. It comes into effect just before the beginning of your turn in the round after you began casting the spell. You then act normally after the spell is completed.

A spell that takes 1 minute to cast comes into effect just before your turn 1 minute later (and for each of those 10 rounds, you are casting a spell as a full-round action). These actions must be consecutive and uninterrupted, or the spell automatically fails.

When you begin a spell that takes 1 round or longer to cast, you must continue the invocations, gestures, and concentration from 1 round to just before your turn in the next round (at least). If you lose concentration after starting the spell and before it is complete, you lose the spell.

You only provoke attacks of opportunity when you begin casting a spell, even though you might continue casting for at least 1 full round. While casting a spell, you don't threaten any squares around you.

This action is otherwise identical to the cast a spell action described under Standard Actions.

Casting a Metamagic Spell

Sorcerers and bards must take more time to cast a metamagic spell (one enhanced by a metamagic feat) than a regular spell. If a spell's normal casting time is 1 standard action, casting a metamagic version of the spell is a full-round action for a sorcerer or bard (except for spells modified by the Quicken Spell feat, which take 1 swift action to cast). Note that this isn't the same as a spell with a 1-round casting time. Spells that take a full-round action to cast take effect in the same round that you begin casting, and you are not required to continue the invocations, gestures, and concentration until your next turn. For spells with a longer casting time, it takes an extra full-round action to cast the metamagic spell.

Clerics and druids must take more time to spontaneously cast a metamagic version of a cure, inflict, or summon spell. Spontaneously casting a metamagic version of a spell with a casting time of 1 standard action is a full-round action, and spells with longer casting times take an extra full-round action to cast.

[Mathmuse]

Read the sentences I bolded in the "Casting a Metamagic Spell" from the Combat chapter of the Core Rulebook.

Core Rulebook, Combat wrote:

Casting a Metamagic Spell

Sorcerers and bards must take more time to cast a metamagic spell (one enhanced by a metamagic feat) than a regular spell. If a spell's normal casting time is 1 standard action, casting a metamagic version of the spell is a full-round action for a sorcerer or bard (except for spells modified by the Quicken Spell feat, which take 1 swift action to cast). Note that this isn't the same as a spell with a 1-round casting time. Spells that take a full-round action to cast take effect in the same round that you begin casting, and you are not required to continue the invocations, gestures, and concentration until your next turn. For spells with a longer casting time, it takes an extra full-round action to cast the metamagic spell.

The line from the Magic chapter,

Core Rulebook, Magic wrote:

Cast a Spell

A spell that takes one round to cast is a full-round action. It comes into effect just before the beginning of your turn in the round after you began casting the spell. You then act normally after the spell is completed.

means that if a spell has a casting time of 1 round, then the caster uses full-round action to start casting, and the casting continues after that full-round action all the way to the beginning of the caster's next turn, too.

The choice of phrases for these rules, one duration called a full-round action and the other duration called 1 full round, is confusing because the phrases are too similar, but they mean different things.

[Adaff]

I guess where I get confused is in the begining. "A spell that takes one round to cast is a full-round action. It comes into effect just before the beginning of your turn in the round after you began casting the spell. " I guess the full round and full round action distinction is really confusing me.

So metamagic full round is different is different than regular full round action?

[Paladin of Baha-who?]

A 1 round casting time is a full-round action, AND doesn't come into effect until the beginning of your next turn. A spell with a casting time of a full-round action comes into effect as soon as that full-round action is complete.

[Mathmuse]

Adaff wrote:

So metamagic full round is different is different than regular full round action?

No. Spontaneous metamagic takes a regular full-round action. The metamagic full-round action is different from the regular spellcasting casting time of 1 full round.

For example, spontaneously casting a Magic Missile, with casting time listed as 1 standard action, as a still spell takes a full-round action and takes effect at the end of that action on the same turn. Casting Enlarge Person, a spell with casting time listed as 1 round, takes a full-round action to start casting, but is not finished at the end of the action. Instead, it is finished at the beginning of the caster's next turn. Summon Monster is another popular spell with a casting time of 1 round.

[Chess Pwn]

Full round action is your standard and your move. It is started and finished all on your turn. So doing metamagic uses your move and your standard but the spell goes off during your turn that you started to cast it.