This is a question that gets asked frequently, and the answer is pretty simple:
The LED, LCD, IR3, Speed, A4, A4 Fly, 05 Speed and G7 all use "Old Style"/"Original"/"G7" Angel threads. The G7 Fly and 06 Speed (including the Ga+) use "New Style"/"06"/"G7 Fly" Angel threads. The A1 uses the same threading as the "06" barrels, but the shank after the threads is shorter. This means that an A1 barrel used on an "06 style" gun will result in a gap between the end of the barrel and the beginning of the breech (too short), and that an "06" barrel used on an A1 will result in a small amount of threading being exposed (too long). The difference between threads is easy to distinguish: The "Original" style uses coarser threads with a much longer shank, while the "06" style uses much finer threads (more like 'cocker threads) and a shorter shank.
Here are pics to illustrate the different types of threading:
New Style/06/G7 Fly: