SAG MK4 Upgrade Kit - Gas Tube Upper + Rear Cover (for MK1 Handguard Owners)
- $719.00
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SAG MK4 Upgrade Kit - Gas Tube Upper + Rear Cover
CNC-Machined Aluminum | Integrated Gas Tube Upper | Removable 1913 Rear Cover | Fits All MK1 Platform Versions
Overview
If you already own an MK1 handguard, this kit is the cheaper route to an MK4. It supplies the two pieces the MK1 does not have: the gas tube upper with its integrated 1913 monorail section, and the removable rear receiver cover carrying a further 1913 segment.
Fitted together with the handguard you already have, the result is a full MK4 chassis - free-floating barrel inside a tubular handguard, and a continuous 1913-MIL-STD top monorail from the gas block back over the receiver.
The kit is universal across MK1 platform versions: AK-pattern, Saiga-308 and VPO/Molot handguards all take it. The MK1 handguard itself is not included. As with the complete MK4, the assembled chassis must be fitted in a specialist workshop on full-size carbines built on certain Molot Arms receivers (MA-136-02, MA-136C, MA-136-05).
This Is an Upgrade Kit - Not a Complete Chassis
The kit includes only the gas tube upper and the removable rear cover. The MK1 handguard block is NOT included - you must already own an MK1 handguard. If you don't have an MK1, choose the complete MK4 chassis instead (available as a separate product).
Key Advantages
- Converts MK1 to MK4 - complete the chassis architecture you already started
- Universal fit - works with all MK1 platform versions
- Integrated gas tube upper - continuous 1913 monorail over barrel and receiver
- Removable rear cover rail - 1913 segment for magnifier or NV attachment
- Cost-effective - upgrade without re-buying the handguard block
- CNC-machined aluminum - matches your MK1 in quality and finish
Technical Specifications
| Material | High-Strength Aluminum Alloy (CNC-milled) |
| Product Code | SAG-S20132 |
| Kit Contents | Gas tube upper + removable rear receiver cover |
| Requires | MK1 handguard (any platform version) - not included |
| Rear Cover Rail | 1913-MIL-STD segment (removable section) |
| Result | Full MK4 chassis: free-floating barrel + continuous 1913 top monorail |
Compatibility
Universal - fits all MK1 handguard platform versions (AK-pattern, Saiga-308, VPO/Molot). See the compatibility filter on this page.
Important: The assembled chassis is not suitable for self-installation on full-size carbines built on certain Molot Arms AK-pattern receivers (MA-136-02, MA-136C, MA-136-05). For those platforms, installation must be performed in a specialist workshop.
What's in the Box
- (1) Gas Tube Upper (integrated 1913 monorail section)
- (1) Removable Rear Receiver Cover (with 1913 segment)
- (1) Mounting Hardware Set
- (1) Installation Manual
Note: MK1 handguard block NOT included.
Frequently Asked Questions
Upgrade Your MK1 to a Full MK4
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SAG Specs
General
Recommended
SAG, Sureshot Armament, MK4 Upgrade Kit, Upgrade Kit, Gas Tube Upper, Rear Cover, MK1 Conversion, Chassis Upgrade, 1913 Rail, Chassis Systems, Bazalet