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B51 7.62 NATO models ($2,799)


Our builds combine all the precision and reliability of the original German designs, with American craftsmanship that’s second to none, and the ability to customize your gun to your requirements. Be sure to check out our post on Configurations to see how we can make this gun truly yours, as well as the how to order section to see how we handle ordering and making your firearm.

Please select your desired configuration below. Options marked with a * must be chosen before the product can be added to your cart (button will appear at bottom of page.)

TERMS: $300 deposit required to reserve your gun (Non-Refundable). Balance due when your order is ready to begin being built.

Clear selection

Weld Finish *

Handguard *

Cerakote Finish *

Picatinny Rail *

A picatinny rail welded to the top of the receiver

Extended Magazine Release (EMR)

This will drastically reduce your reloading times by allowing you to release the magazine with your strong hand ( REQUIRES PADDLE MAGAZINE RELEASE FOR ALL MODELS EXCEPT 10/40/357 MODELS)

trigger group upgrade

replaces the SEF trigger pack with an ambidextrious model. Available in 2,3 and 4 position models (All SEMI AUTO ONLY)

Charging Handle

Sig Brace Adapter

With our newly designed end cap, you can now utilize the sig brace on any roller lock firearm.

Trigger Upgrade

Reduces the factory trigger weight to approx. 6 lbs, Polishing of all engagement surfaces, removal of pre & post travel creep

Flip-up Sight Upgrade

Replaces the front & rear sights with a picatinny rail to allow use of Flip up sights

Vortex Optics Package

Adds a 3″ over bore riser with back up sight window & a Vortex SPARC II optic to your order

Grip Stippling

Laser stippled pattern on the trigger housing to improve grip

FFL Submittal

You may upload a copy of the FFL you would like us to ship to. Not required to place an order.

NFA Engraving for Form 1

If you are planning on filing an ATF form 1 to convert your pistol to an SBR, We will do your engraving at the factory. If you would like this upgrade, please enter your desired engraving info below.

SKU: BP51 Category:

Product Description

Each firearm is hand fit, built & fully assembled from start to finish by Brethren Armament using a PTR flat, barrel, trunnion and bolt, with a 100% original HK trigger pack. SBR SHOWN. REQUIRES BATFE PAPERWORK TO CONVERT OR PURCHASE

Each custom BP51 pistol build includes:

  • Brethren Arms’ Proprietary Weldless finish, which makes all visible structural welds invisible, without any reduction in strength or rigidity of the receiver ( Sight base and rail welds will be visible.)
  • PTR properly stamped & rolled upper receiver hand fitted to the Bolt Group, Trunnion and Barrel
  • PTR barrel, chambered in 7.62 NATO ( 7.62X39 also available)
  • PTR 51PDW F/A bolt group complete
  • HK German HK anti rattle mag release
  • HK SEF Navy style trigger group (semi auto)
  • New Cerakote mixture with reduced IR signature
  • Welded Picatinny rail
  • All tested for fitment and function fired on semi and full-auto
  • Comes in a soft tactical case


  • Precision Rifle models (PSG1/MSG90) available
  • custom cerakote schemes- Whatever you can dream up, we can do
  • Ambidextrous selector switch
  • contoured grip
  • South Paw model- a true left hand friendly model complete with port side cocking lever
  • SBR (pictured) with folding stock REQUIRES BATFE TAX STAMP

And anything else you can think of. We have a staff of Engineers and Fabrication specialists that will take on any task



Additional Information

Magazine Release*

Tac-Latch, Ambidextrious Paddle Release

Barrel Length*

5.3″, 8.4″, 12.7″, 16″, 18″


7.62 NATO, 7.62×39


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