WALTHAM — There’s a reason Ray Allen  is regarded as one of the best pure shooters in NBA history: Practice, and lots of it.
Allen’s regiment for shooting nearly matches the same for his conditioning. Allen will spend 45 minutes or longer following practice, just practicing catching and shooting from long range. He’ll usually shoot from both baselines, both wings and from the top of the key. (In the video, he is taking passes from Celtics  assistant coach Tyronn Lue.)
Allen enters Tuesday night’s game vs. Cleveland needing just 24 3-pointers to pass Reggie Miller  (2,560) for first on the all-time list.
He is on pace for 180 this season, which would match his total in 2008, his first season in Boston. Now in his 15th season, Allen has led the NBA in 3-pointers three times in his career, each time passing the 200-mark for a season.
Allen set the all-time single-season NBA record for 3’s in a season when he drained 269 of them in 2005-06 with Seattle, two more than Dennis Scott with the Magic 10 years earlier.
This year, Allen is fifth in both 3-pointers made at 93 through 43 games and 3-point percentage at .452.