WASHINGTON (AP) — The emotions finally flowed for Randy Johnson when the final out was made.

A hug for his son, who was serving as batboy. Hugs for every teammate, plus a really big one for his manager. The game ball presented to his wife as his three daughters beamed with pride. A news conference that lasted a half-hour from a player who usually doesn’t have much to say. Someone even spotted a smile.

The Big Unit admits he can come across as surly, and he did his best over the past few weeks to downplay his pursuit of 300 wins. Once he got there — with a steady, six-inning performance in the San Francisco Giants’ 5-1 victory over the Washington Nationals in the opener of a doubleheader Thursday — he was free to express that, yes, it really is a big deal.

‘‘I think it kind of hit me when I walked on the field,’’ Johnson said. ‘‘It’s a long-range achievement. It’s not a one-game or a one-year achievement, it’s a career achievement. Who knows how many teammates I’ve had over my 21 years, but they had a great deal to do with my success. I’m going to think about this for a long time.’’

In the nightcap, the Giants completed a sweep with a rain-shortened 4-1 victory. The game was called with two outs in the top of the sixth after a 67-minute delay.

Johnson became the 24th pitcher to reach the 300-win milestone, and he did it as a mature pitcher, not the overpowering tangle of arms and legs who was all about strikeouts early in his career. He walked two, struck out two, allowed only an unearned run and threw 50 of his 78 pitches for strikes. He faced four batters above the minimum and got shutout relief from his bullpen.