The BFTA Main Shoot Rules, Rule 3: Equipment testing states that:
(Grand Prix Series Competitions) A minimum of one registering shot and a maximum of 3 registering shots will be allowed over the chronograph, if the gun registers over the Current Legal Limit the shooter will be asked to remove the gun from the course. If the gun registers over the BFTA Limit but under the Current Legal Limit the shooter will receive a YELLOW CARD. On the issue of the first YELLOW CARD the shooter will receive a warning, will be allowed to carry on with the Competition and his/her score will count. On the issue of a second or subsequent YELLOW CARD during the season the score will be void.