Comstock Armory 5.56/.308 Quick Detach Recessed Plan-B HUB Suppressor Mounting Kit

Comstock Armory 5.56/.308 Quick Detach Recessed Plan-B HUB Suppressor Mounting Kit

The Comstock Armory 5.56/.308 Quick Detach Recessed Plan-B HUB Suppressor Mounting Kit brings two different barrel-thread configurations into one matched mounting package. It includes one 1/2x28 .223/5.56 recessed micro brake, one 5/8x24 .30-caliber recessed micro brake and one steel RPA HUB adapter for a compatible suppressor rated for both firearms.

This kit contains everything you need in mounting hardware to mount your compatible HUB suppressor to one 1/2x28-threaded 5.56 firearm and one 5/8x24-threaded .30-caliber firearm while keeping an ultra-tight, low-profile mounting system. The mixed brake pair equips one firearm of each thread configuration.

Shop this Comstock Armory 5.56/.308 mounting kit at BattleHawk Armory for a compact Plan-B setup across two compatible firearms.

Kit Contains

• 1x Comstock Armory Recessed Micro Plan-B Muzzle Brake, 5/8x24, .30 Cal, Black Nitride - SKU: MBM-58-30-R - UPC: 850069580315
• 1x Comstock Armory Recessed Micro Plan-B Muzzle Brake, 1/2x28, 5.56, Black Nitride - SKU: MBM-12-22-R - UPC: 850069580308
• 1x Comstock Armory RPA HUB Recessed Plan-B Suppressor Adapter, Stainless Steel - SKU: RPA-B-SS - UPC: 850069580285

The package contains three mounting components: two muzzle brakes and one suppressor adapter. Firearms and a suppressor are not included.

Recessed Plan-B HUB Mounting

The RPA-B-SS adapter connects a compatible 1.375-24 HUB/Bravo suppressor to the included Plan-B-pattern muzzle devices. Its recessed profile positions the muzzle device 0.40 inch deeper than the standard Comstock LPA, shortening the assembled mounting configuration and helping create a tighter handguard-to-suppressor gap. The adapter itself adds 0.18 inch of length and weighs 2.1 ounces.

One adapter serves the compatible suppressor while the two brakes provide matching attachment points on two firearms. Quick-detach convenience and the recessed profile work together for a compact system. Actual spacing depends on the firearm, muzzle device and suppressor combination.

One 5.56 Brake and One .30-Caliber Brake

The MBM-12-22-R brake uses 1/2x28 threads, supports .223/5.56 projectiles and weighs 1.5 ounces. The MBM-58-30-R brake uses 5/8x24 threads, accepts bullets up to .308/7.62mm and weighs 1.2 ounces. Each measures 1.25 inches overall and adds 0.42 inch beyond the muzzle. The common Plan-B interface serves a mixed firearm collection without requiring both barrels to have the same thread pitch.

The recessed micro brake design reduces recoil and acts as a sacrificial surface ahead of the suppressor blast baffle. Its rotationally symmetric geometry does not require timing with shims. Limited forward protrusion is useful with the recessed adapter, while the complete combination still requires adequate internal clearance.

17-4 PH Stainless Steel and Black Nitride

Both muzzle brakes and the RPA adapter use 17-4 PH stainless steel with a black nitride finish. The kit pairs professional-grade steel components with a consistent black appearance. The included adapter is the steel RPA-B-SS configuration, with the same material and finish family as the recessed micro brakes.

Compatibility and Clearance

The .223/5.56 brake belongs on the compatible 1/2x28 firearm, while the .30-caliber brake belongs on the compatible 5/8x24 firearm. Both require barrel diameters of 0.750 inch or less where the recessed bodies overlap the barrels. The shared suppressor must have a compatible 1.375-24 HUB/Bravo rear interface and be rated for both cartridges and barrel lengths. Confirm blast-chamber and handguard clearance on each firearm.

Product Specifications

• Component manufacturer: Comstock Armory
• Configuration: 5.56/.308 Recessed Plan-B HUB Mounting Kit
• Included hardware: Two recessed micro muzzle brakes and one steel RPA adapter
• Barrel threads: 1x 1/2x28 .223/5.56 brake; 1x 5/8x24 .30-caliber brake
• Caliber / bore limits: .223/5.56mm on the 1/2x28 brake; up to .308/7.62mm on the 5/8x24 brake
• Suppressor rear interface: 1.375-24 HUB/Bravo
• Muzzle-device interface: Plan-B pattern
• Material / finish: 17-4 PH stainless steel / black nitride
• Brake length: 1.25 inches overall; 0.42 inch added beyond the muzzle
• RPA profile: 0.18 inch added adapter length; muzzle device sits 0.40 inch deeper than with the standard LPA
• Maximum barrel diameter at brake recess: 0.750 inch
• Component weights: 1.5 oz 5.56 brake; 1.2 oz .30-caliber brake; 2.1 oz adapter

Frequently Asked Questions

Can one suppressor serve both firearms?

Yes, when that suppressor is rated for both cartridges and barrel lengths and has suitable bore and internal clearance. The included adapter provides the common mount. A suppressor rated only for 5.56 does not become .308-compatible through this kit.

Does this package include two suppressor adapters?

No. It includes two muzzle brakes and one RPA-B-SS adapter. The package supplies two firearm-side mounting points for one compatible suppressor.

Does HUB threading alone guarantee fit?

No. Matching rear threads are one requirement. The recessed mounting position also requires suitable blast-chamber depth, handguard clearance, barrel dimensions and caliber compatibility.

Order the Comstock Armory 5.56/.308 Quick Detach Recessed Plan-B HUB Suppressor Mounting Kit from BattleHawk Armory. Bring matching recessed components together in one specialized package for your two compatible firearms.