Actually it is not. They get 1.7% of their high three average yearly pay per year of service they have (after 5 years of service) payable once they reach 62 years of age. (those sworn in after Dec 31, 2012 get 1% per year).
So he'd get 13.6% of his high three average (so about $21K a year) Not counting any thrift savings plan investments he may have made.
Perhaps the confusion is with the words “full pension”
Under the old CSRS pension system an employee (including a congressman) received a full (or maximum) pension after 41 years 11 months of service. (80% of their high 3 average yearly pay)
For FERS there is no such thing. You get a set percentage for every year of service and the longer you work the more you get as a pension. There is no such thing as a “full Pension” under FERS.