The Weaver #40AM Top-Mount Scope Base (Weaver part no. 48428) is machined for the BSA Monarch along with select Colt and Remington rifles, giving them a factory-tight platform for a riflescope. Weaver cuts the base from aluminum and finishes it in a black matte that cuts glare in the field. Because it’s machined to the exact screw pattern shared across this fit list, it bolts straight to the factory holes with no drilling or gunsmithing needed. This is the correct base to start with if you’re mounting glass on a BSA Monarch or a compatible Colt or Remington bolt rifle.

Key Specifications

• Purpose-built to fit the BSA Monarch, matching the receiver’s factory-drilled screw pattern.
• Also fits select Colt and Remington rifles sharing the same hole pattern.
• Listed as a 1-piece base, so a single component bridges the full mounting area.
• Positioned as the rear base on the receiver for correct scope eye relief.
• Uses Weaver’s To Receiver mount style, bolting directly to the factory tapped holes.
• Finished in black matte to cut glare in the field.
• Machined from aluminum for a lightweight, corrosion-resistant base.
• Requires Weaver-style rings to complete the mount.
• Cross-references as Weaver Application #40AM on the brand’s official fit chart.

Frequently Asked Questions

What rifles does this base fit? It’s machined for the BSA Monarch along with select Colt and Remington rifles, listed under Weaver’s Application #40AM.

Are scope rings included? No, this is the base only; pair it with a set of Weaver-style rings to finish the mount.

Does it require any gunsmithing to install? No, it bolts directly to the factory screw holes on these receivers.

Buy the Weaver #40AM Top-Mount Scope Base for BSA Monarch, Colt, and Remington

A base machined to the exact receiver pattern keeps a scope tracking true shot after shot, and this Weaver #40AM bolts straight to a BSA Monarch or compatible Colt or Remington rifle with no modification. Order it from our Lubbock, Texas gun shop and it ships fast to your door, along with more scope bases and mounting hardware.