2. 2
LP 300 Blackout Parts Nomenclature
Gas BlockReturn Spring Piston CylinderPistonSpring Guide
Bolt AssemblyBolt Carrier
Bolt Carrier Buffer
Cam Pin
3. 3
Low Profile 300 Blackout Disassembly
Always confirm that the firearm is unloaded before beginning disassembly. Start by removing the
upper receiver from the lower receiver. Remove the bolt carrier group from the upper. Fig. 1
Figure 2
Figure 1
Remove the hand guard retaining screws and remove hand guard by pulling it forwards straight off
the end of the barrel. Figs. 2
4. 4
Low Profile 300 Blackout Disassembly Continued
With the hand guard removed align the piston alignment slot with the op-rod take down hole.
Fig. 1
Figure 1
5. 5
Low Profile 300 Blackout Disassembly Continued
Insert a punch or similar tool into the op-rod takedown hole, pull back on the op-rod until it
clears the piston. Fig. 1
Figure 1
6. 6
Low Profile 300 Blackout Disassembly Continued
With the op-rod clear of the piston lift up and forward removing the op-rod over the top of the
piston and free from the upper. Fig. 1
Figure 1
7. 7
Low Profile 300 Blackout Disassembly Continued
Pull the piston rearward and removing it from the piston cylinder and that completes the
disassembly procedure for the LP 300 Blackout piston system. Fig. 1
Figure 1
8. 8
Low Profile 300 Blackout Disassembly Continued
Cleaning and Maintenance
• For quick field cleaning simply wipe out the upper receiver and wipe off the bolt carrier with a rag, add
a few drops of lubricant to the carrier and reassemble.
• For a thorough cleaning disassemble the piston system assembly in to its individual parts and with a gun
cleaner of your choice follow the brands cleaning instructions. For detailed cleaning instruction for your
AR-15 type rifle we recommend consulting a US military technical manual such as ARMY TM 9-1005-
319-23&P
• Most owners will clean and maintain their piston system well above what is required. For others who
use the piston system daily they may only do a thorough cleaning when reliability suffers. Although the
piston system in daily use is nearly maintenance free, we do recommend routine inspection and cleaning
as needed to prevent corrosion. The piston system should be thoroughly cleaned and lubricated before
lengthy storage to prevent corrosion.
• We recommend wiping off any excess lubricant from the piston and piston cylinder before placing the
system in service because excess lubricant accelerates fouling buildup by providing a base for fouling to
adhere to then it burns off leaving only burnt on carbon / fouling behind.
• The use of corrosive ammunition is not recommended and if ever used will require an immediate and
extensive cleaning process to prevent corrosion. The corrosive ammunition cleaning process is beyond
the scope of this manual and customers are advised not to use corrosive ammunition.
• Do NOT use Ammonia base products on Nickel Boron Carrier.
9. 9
Low Profile 300 Blackout Reassembly
For reassembly simply reverse the order that was used for disassembly. Refer to the following
steps and pages, if needed, to complete reassembly.
Step 1) Return the piston back inside the piston cylinder.
10. 10
Step 2) Place the small end of the op-rod into the upper receiver and push the op-rod
rearward until it clears the piston.
Low Profile 300 Blackout Reassembly Continued
11. 11
Step 3) With the op-rod clear of the piston allow the op-rod to be captured within the piston
head under spring tension.
Low Profile 300 Blackout Reassembly Continued
12. 12
Step 4) Reinstall the hand guard and secure with hand guard retaining screws.
Low Profile 300 Blackout Reassembly Continued
13. 13
Low Profile 300 Blackout Features:
– Requires no regulators
– Cycles subsonic ammo with or without a silencer
– Cycles supersonic ammo with or without a silencer
– Has a self regulating gas piston operating system
For more information on Black Rifle Arms products please visit us at:
Online Store: www.blackriflearms.com
YouTube Channel: http://www.youtube.com/user/BlackRifleArms
Facebook Page: https://www.facebook.com/blackriflearms
Black Rifle Arms
New Smyrna Beach, FL 32168
386.428.7960
