Did he do that with the entire federal government or just part of it? I know that TVA changed retirement systems under Reagan, but all the older employees on the "old" defined-benefit plan are still on that plan, while newer employees are on the newer "defined-contribution" plan.
Also, that the contribution to the new retirement plan do not come from the employee's pay but is an additional sum based on their pay. They also have social security and a 401K though.
The FERS system has the employee paying social security premiums at 7%, plus the Federal Government pays an automatic 1% in the Govt. 401(k) plan [called Thrift Savings Plan] but it will match up to 5% of what the employee contributes in their 401(k). So an employee can put in 5% and the Govt. will match the 5%. This is very similar to big business where the Company provides matching contributions. Heck, even my parents and their small business did something similar.
Reagan had said the annuity retirement plan (CSRS) had to be replaced or it would fail of its own weight. Now that was 26 years ago. Reagan did the right thing. Plus now I believe the employees are more mobile. When I worked, I could not take my CSRS pension with me to the private sector. That was another issue Reagan tried to fix.
Hope this helps.