The 21-year-old centre-back will stay with the Stones until the end of the season.
Finney is an aggressive defender who began his career with Leyton Orient.
In 2014 Bolton Wanderers brought him to their academy set up and he made his debut for the Whites where he was consistently on the verge of the first-team and made three appearances before being released so they could accommodate another signing.
He signed for the R’s a couple months later and was a regular for the under-23’s during last season
Finney spent the first half of the season at the Gallagher Stadium, making fifteen appearances and scoring one goal