[straube]

For the GCC we need to find a natural use for 1M-2D in concert with 1M-2C as an artificial GF. To be natural, 2D must promise 3+ diamonds.

How about 1M-2M being a constructive raise and 1M-2D being a simple raise with 3+ diamonds? I looked at 25 suitable hands for a simple raise and 20 of them had 3+ diamonds (looking at spade auctions specifically) so that's 80%. The other simple raise hands would have to bid 1N.

This is backwards from ideal. We want 1M-2M to be that bad raise, but it's GCC friendly.

[glen]

straube, on 2011-March-13, 12:30, said:

... To be natural, 2D must promise 3+ diamonds. How about 1M-2M being a constructive raise and 1M-2D being a simple raise with 3+ diamonds? ...

This is actually a convention, and not GCC legal. The 2♦ bid shows 3+♦s and 3 in the major, and it becomes a convention when you promise length in a suit not bid. A GCC legal treatment would 2♦ as a simple raise with 3+♦s or a shapely slam try with 5+♦s that wants to show hand type to opener.

straube, on 2011-March-13, 12:30, said:

... The other simple raise hands would have to bid 1N. ...

Instead have the simple raise short ♦ hands mostly bid 2M, the exception is that any 4432 with 2♦s bids 1NT (or 1♠ over 1♥). Thus 1M-2M is either a constructive raise, or a simple raise with short ♦s and some shape values. Over this, play a bid such as 3♦ as asking responder to bid 3M with the simple raise, and 4M on all constructive raises. You will rarely hit the bad scenario when opener has enough to invite opposite the constructive raise, but gets to 3M down opposite the simple raise, since 80% of the time the simple raise will bid 1M-2♦, and otherwise the simple raise will be shapely enough to provide ruffing options.

[straube]

Can it show 3+ diamonds and 3+ trump OR 13 diamonds? That doesn't promise length in a suit not bid. I hate the GCC

[awm]

It may be worth mentioning that the GCC and related rulings are not at all consistent about this point.

There are certainly cases (like 2M showing five in the bid suit and a four-card minor, 2♥ showing both majors, etc) where openings which show length in some other suit are ruled illegal even though they are natural bids. However, there are other cases (like 2M weak showing five or six in the bid suit and two or three in the other major) where such openings are ruled legal. When queried about this the typical responses go something like: "of course XXX is not allowed, it's a convention and not specifically legal.... of course YYY is allowed, it's a natural bid."

In any case, I suspect that the method you are proposing (2♦ shows a raise of partner's major in some point range with 3+♦ also) is in the spirit of things that would not be allowed. Hard to know for sure though (and may depend on the director).

[rbforster]

Its a fit-non-jump!

I'd go with 2D as the constructive raise and 2M as the weaker one, for preemption purposes. After all, there shouldn't be a different in the number of diamonds in either of them, right? Especially if you have various jump raises for 4+ major raises, your average 3 card raise will have 3.3 diamonds. Still, i suppose having 2D be weaker is a little less risky for the times when you don't have 3 diamonds and have to bid 1N (since you might miss more if that's semi forcing and partner could have the constructive raise).