Medium should work for you, these can be stretched slightly due to being leather.
You're on the borderline between large and extra large, since these are leather, you might be able to work the large to fit, but if you want a guaranteed fit the extra large is the safer bet.
The dimensions are as follows:
Small: 5in Length, 1.5in Width
Medium: 5 3/16in Length, 1 1/2in Width
Large: 5 5/16" Length, 1 5/8" Width
X-Large: 5 1/2in Length, 1 13/16in Width
You will have to measure the stock on your rifle to determine which one will fit best.
This could help, it will add 1/2" to the length of the stock.
The dimensions are as follows:
Small: 5in Length, 1.5in Width
Medium: 5 3/16in Length, 1 1/2in Width
Large: 5 5/16" Length, 1 5/8" Width
X-Large: 5 1/2in Length, 1 13/16in Width
You will have to measure the stock on your rifle to determine which one will fit best.