The Rail Mounted Adjustable Bag Rider SQR Bottom
From these dimensions you can figure out if the Rail Mounted ABR fits your application.
Rail Mounted Adjustable Bag Rider Measurement for Rimfire. And additional .394” can be added to the above .943” to remove the minimal amount that would touch if the next forward mounting slot is used.
RPRR modification. 3/8” End Mill, round file, Dremel…. centered and .125” to .135” deep