AR 15 troubleshooting guide

Most semi-automatic rifles operate using the same or in a similar method. However, each manufacturer has their own troubleshooting procedures. However, use this AR 15 troubleshooting guide to help you start working through any issues you may encounter. The AR 10 is extremely similar (the AR 15 is a redesigned AR 10) and this guide should work on your AR 10 as well. 

There are many manufacturers of AR 15s and AR 10s as well as models for those manufacturers. For this AR 15 troubleshooting guide, I have compiled a list of procedures for troubleshooting the most common issues in the following table. This is by no means a complete list of troubleshooting steps but is a good starting point for the most common issues that you may encounter. 

To use the AR 15 troubleshooting guide, find your problem in the first column of the table, then try the causes starting from the top and working down. If you reach the bottom of the problem and your firearm is still not functioning correctly, you should seek the advice of the Manufacturer or an Armorer certified by the manufacturer for that model.  

Problem Cause Correction
Bolt carrier group fails to lock to the rear after last round 1 - Dirty or corroded bolt latch Disassembly and clean
2 - Defective magazine catch spring Replace spring
3 - Worn or broken magazine catch Replace magazine catch
4 - Magazine follower worn or broken Replace follower
5 - Magazine spring weak or broken Replace spring
6 - Magazine feeder lips bent or broken Replace magazine
7 - Magazine follower binds during operation Replace follower. If problem still exists replace magazine
8 - Broken bolt catch and/or spring Replace bolt catch and/or spring
Failure to Feed 1 - Magazine catch spring weak or broken Replace magazine catch spring
2 - Magazine catch defective Replace magazine catch
3 - Magazine catch out of adjustment Adjust magazine catch to capture magazine
4 - Magazine catch notch defective Replace magazine
5 - Magazine lips burred or broken Replace magazine
6 - Magazine follower defective, or binds during operation. Replace magazine
7 - Magazine spring weak or broken Replace magazine
8 - Magazine tube dented Replace magazine
9 - Short recoil See short recoil below
Failure to Chamber 1 - Weak or broken buffer spring Replace spring
2 - double feed Remove obstruction
Failure to lock 1 - Dirty or damaged ammunition Replace ammunition
2 - Bolt cam pin broken or missing Replace bolt cam pin
3 - Loose or damaged bolt carrier key Tighten
4 - Improperly assembled extractor srping assembly Assemble correctly
5 - Bent gas tube Adjust/bend gas tube in area of the handguard to its original configuration or replace
6 - Weak or broken buffer spring Replace spring
Failure to fire 1 - Broken, chipped, or deformed firing pin Replace fireing pin
2 - Firing mechanism and/or lower receiver assembly improperly assembled or has worn, broken, or missing parts Inspect fire control components including hammer and trigger. Replace worn or broken parts
3 - Broken, missing, or defective retaining pin Replace Pin
Failure to unlock 1 - Burred Locking lugs on bolt assembly Replace bolt assembly
2 - Burred locking lugs on barrel extension. Replace barrel
3 - Short recoil See short recoil below
4 - Broken bolt assembly Replace Bolt
Failure to extract 1 - Defective extractor pin, extractor , and/or extractor spring assembly Replace
2 - Short recoil See short recoil below
3 - Badly pitted chamber Replace barrel
Failure to eject 1 -Broken or missing cartridge ejector Replace ejector
2 - Ejector stuck in bolt body Disassemble and clean
3 - Weak, broken or missing ejector spring Replace ejector spring
4 - Short recoil See short recoil below
Failure to cock 1 - Worn, broken, or missing parts of firing mechanism Inspect fire control components including hammer and trigger. Replace worn or broken parts
2 - Short recoil
Short recoil 1 - Improper gap space or worn, missing or broken bolt rings Take to gunsmith
2 - Partially plugged gas system because of carbon build up in gas tube Clean or replace gas tube and/or gas block
3 - Carbon buildup in the narrow passage of the bolt carrier key Clean
4 - Gas leakage caused by broken or loose gas tube around front sight base Replace gas tube and/or gas block
5 - Improper alignment of gas tube and carrier key Take to gunsmith
6 - Loose carrier key Tighten and stake screws on carrier key