AR-15 Parts List

I’ve had a Smith & Wesson M&P 15 for a few years now. However, only recently have I really taken the time to learn about how it works and to learn how to fully take it down and build it up again. Below is a full breakdown of each pin, spring and part that makes up an AR-15.

NOTE: The beauty of the AR-15 platform is the fact that they are amazingly uniform. In fact, you can (and people often do) mix and match parts from different manufacturers.



# 23 – Charging handle latch roll pin
# 24 – Charging handle latch
# 25 – Charging handle latch spring
# 26 – Charging handle
# 27 – Firing pin
# 28 – Bolt carrier key screw, each (2 required)
# 29 – Bolt carrier key
# 30 – Firing pin retaining pin
# 31 – Cam pin
# 32 – Bolt carrier, Semi-auto
# 33 – Bolt gas ring, improved, each (3 required)
# 34 – Bolt
# 35 – Extractor spring
# 36 – Extractor spring insert
# 37 – Extractor
# 38 – Extractor pin
# 39 – Ejector roll pin
# 40 – Ejector spring
# 41 – Ejector
# 42 – Forward Assist Assembly
# 43 – Pawl spring pin
# 44 – Pawl spring
# 45 – Pawl detent
# 46 – Forward assist pawl
# 47 – Forward assist spring
# 48 – Ejection port cover
# 49 – Ejection port cover spring
# 50 – Ejection port cover pin
# 51 – Pin retaining ring
# 52 – Upper Receiver
# 53 – Rear sight elevation spring pin
# 54 – Forward assist spring pin
# 55 – Rear sight elevation spring
# 56 – Rear sight elevation knob
# 57 – Rear sight elevation index
# 58 – Index screw
# 59 – Rear sight assembly
# 60 – Ball bearing
# 61 – Elevation index spring
# 62 – Rear sight windage knob
# 63 – Rear sight windage knob pin
# 64 – Rear sight index spring
# 65 – Rear sight ball bearing
# 66 – Rear sight flat spring
# 67 – Rear sight aperture
# 68 – Rear sight ball bearing
# 69 – Rear sight helical spring
# 70 – Rear sight base
# 71 – Rear sight windage screw



# 72 – Action spring
# 73 – Buttcap spacer
# 74 – Buttstock,
# 75 – Buttplate
# 76 – Buttplate screw
# 77 – Trap Door Assembly, plastic
# 78 – Rear swivel screw
# 79 – Trap door hinge pin
# 80 – Trap door hinge
# 81 – Rear sling swivel
# 82 – Pistol grip screw
# 83 – Lock washer
# 84 – Pistol Grip
# 85 – Safety detent spring
# 86 – Safety detent
# 87 – Hammer and trigger pin (2 required)
# 88 – Magazine release button
# 89 – Magazine catch spring
# 90 – Trigger guard pivot roll pin
# 91 – Trigger guard
# 92 – Trigger spring
# 93 – Trigger, standard
# 94 – Disconnector
# 95 – Disconnector spring
# 96 – Pivot pin
# 97 – Pivot pin spring
# 98 – Pivot pin detent
# 99 – Magazine Catch
# 100 – Bolt catch spring
# 101 – Bolt catch plunger
# 102 – Bolt catch roll pin
# 103 – Bolt catch
# 104 – Safety selector lever
# 105 – Hammer spring
# 106 – Hammer with J pin, standard
# 107 – Buffer assembly
# 108 – Buffer retainer
# 109 – Buffer retainer spring
# 110 – Takedown pin spring
# 111 – Takedown pin detent
# 112 – Takedown pin
# 113 – Receiver extension




A – Extractor Pin
B – Extractor
C – Extractor Spring Assembly
D – Ejector Roll Pin
E – Ejector
F – Ejector Spring
G – Bolt Gas Rings
H – Bolt
I – Firing Pin
J – Firing Pin Retaining Pin
K – Cam Pin
L – Bolt Carrier Key
M – Bolt Carrier Key Screws
N – Bolt
O – Bolt Carrier




A – Handguard Snap Ring
B – Weld Spring
C – Handguard Slip Ring
D – Gas Tube Roll Pin
E – Gas Tube
F – Handguard Cap
G – Crush Washer
H – Muzzle Brake/Flash Suppressor

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Author:TechPrepper

A nerd on a journey to learn how to survive TEOTWAWKI and WTSHTF
  • http://www.prepplace.blogspot.com badvoodoodaddy

    Great weapons. A bit on the expensive side for me. I don’t like the fact that they have so many parts to clean though, but I can do this sucker blind folded now. I carried an M-16 for many years in the service. I like the SKS for its simplicity and few parts to clean. Great info though for those thinking about getting an AR platform.

    • http://techprepper.com TechPrepper

      You aren’t wrong about it’s complexity. I’m still trying to find a Trigger Pin that popped off somewhere while I was taking it down for the first time. Basic field cleaning just doesn’t cut it … there was carbon EVERYWHERE. When you were in the service and used the weapon regularly, did you ever have to take it down fully or did the basics keep it clean enough to function reliably?

  • Joshua

    Unless one is an armorer, military members are only allowed to do the basic field strip. All of the detail cleaning still must be done without removing the fire control parts…. think lots of pipe cleaners and q-tips.

    • http://techprepper.com TechPrepper

      That makes a lot of sense. They are very complicated to assemble without the right tools and the springs are tricky at the best of times.

  • Shermdog

    I think you have the barrel parts and bolt/bolt carrier diagram descriptions mixed up.


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