Experienced "red team" security testers routinely claim getting more than 50% of their guns through the check.
Whilst I will be among the first to critisise the quality of training of security staff in most UK airports, I do not blame the staff. I blame the management and their methods. Whatever else, we rely on these poorly paid and poorly trained people to look out for us. As it happens, I am very aware of the type of checking of security operators that takes place at BAA airports in the UK and would not normally comment. However, your claim is completely incorrect and could cause concern to regular travellers. Every day, somewhere in the BAA "empire", attempts are made to breach security through entry points of airports as part of ongoing training. I've never heard of a "red team" but the private agencies who carry out these exercises do not report figures like the one mentioned. Also, it's not called a "gun".