Gamma matches do offer added lightning protection however, several conditions have to be met before you gain any benefit. The radiator must be DC grounded, the antenna must have an extremely good earth ground system and a quality lightning arrestor should be installed on the transmission line just prior to the cable entering the building with its own ground.
The radiator must be DC grounded because otherwise it is likely lightning will still see the path through the gamma match as the least resistance. Most stock gamma matches have a DC break down voltage over 10,000 volts. Many aftermarket models will handle over 50,000 DC volts before flashing over.
In comparison to the voltage of lightning, 50,000 volts is more like a double A battery. Lightning will easily exceed this by many many times. The trick is to keep the voltage drop across your ground system below the breakdown voltage of your gamma match. If the ground is sufficient, it will sink the majority of the current to ground without flashing over the gamma match.
There will still be a pulse of current for a fraction of a second as the gamma match capacitor charges. Many broadcast transmitters can handle this pulse especially if the FPA uses a tube. Nearly every receiver will still suffer damage without a gas discharge type lightning arrestor. If you run an amp, you may still have problems because the discharge tube will have to handle the RF voltage of your amp. If you want to save the rig too, you may need another low power arrestor at the back of the radio.
None of this is a guarantee you will survive a direct strike unscathed although broadcast stations survive these types of strikes in many cases. The gamma match helps, but only if everything else is done correctly first. It does this by providing DC isolation to the transmission line and will still require an exceptional ground system to pull off any real lightning protection.
