AR-15 Troubleshooting Guide

Your AR-15 just failed at the range. Or maybe it is acting weird on the workbench and you need ar-15 troubleshooting help fast. Not theory, not history lessons, not three different explanations of the same problem. This guide cuts straight to what actually works.

Follow the checkboxes. Fix your gun. Get back to shooting.

Quick Diagnosis: Find Your Problem in 30 Seconds

What You See/Hear	Likely Section	Time to Fix
Round stuck on feed ramp, nose diving, or bolt rides over	Failure to Feed	2-10 minutes
Click when trigger pulled, no bang, primer dented	Failure to Fire	5-20 minutes
Spent brass sticking out, weak ejection, or brass to face	Failure to Eject	5-15 minutes
Two rounds visible, one stuck in chamber (double feed)	Failure to Extract	5-20 minutes
Bolt sluggish, won’t lock open, short-stroking	Failure to Cycle	2-15 minutes
Trigger dead, won’t move forward after shot	Trigger Won’t Reset	10-40 minutes

Tools Required by Section

Malfunction Type	Field Kit	Workbench Tools	Parts Needed
Feeding	Cleaning kit, mags	Calipers, brass brush	Mag springs (rarely)
Firing	None	Headspace gauges	Hammer spring
Ejection	None	Extractor tool	Extractor spring, O-ring
Extraction	None	Cleaning rod, brush	Extractor assembly
Cycling	None	Vise block, calipers	Buffer, gas rings
Trigger	None	Punch set	Spring, disconnector

Recommended Tools for AR-15 Troubleshooting

Here are the tools and parts referenced in this guide:

Workbench Pick

AR-15 Complete Cleaning Kit

Comprehensive AR-15 cleaning to prevent fouling-related malfunctions

Check Price

Workbench Pick

AR-15 Chamber Brush – Brass/Nylon

Remove chamber carbon to fix extraction and feeding problems

Check Price

Workbench Pick

AR-15 Headspace Gauges – GO/NO-GO Set

Measure chamber headspace for safe ignition and function

Check Price

Workbench Pick

AR-15 Upper Receiver Vise Block

Secure upper receiver for safe maintenance and assembly work

Check Price

Workbench Pick

AR-15 Roll Pin Punch Set

Proper roll pin punches for safe AR-15 assembly

Check Price

Workbench Pick

AR-15 Bench Block

Protective support block for AR-15 pin installation

Check Price

Workbench Pick

AR-15 Extractor Spring and O-Ring

Fix weak extraction with upgraded spring and O-ring

Check Price

Workbench Pick

AR-15 H/H2 Buffer

Buffer weight upgrade to tune cycling and reduce over-gassing

Check Price

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⚠ IS YOUR AR-15 SAFE?

STOP. CLEAR. VERIFY. Before you do anything else.

• Magazine removed
• Chamber empty (visual + finger check)
• Bolt locked back

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⚠ CRITICAL: Chamber Compatibility Can Kill You

5.56 NATO vs .223 Remington vs .223 Wylde. These are NOT interchangeable. 5.56 NATO generates higher pressure than .223 chambers can handle.

The Rule:

• .223 Remington: Shoot .223 only
• 5.56 NATO: Shoot 5.56 OR .223
• .223 Wylde: Shoot both safely

Check barrel marking BEFORE loading ANY ammunition.

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WHAT IS YOUR AR-15 DOING?

Click your symptom. Jump straight to the fix.

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Failure to Feed: Round Won’t Chamber

Symptom: Round jams on feed ramp, nose-dives into magazine, or bolt rides over top round.

Step 1: Field Check (30 seconds)

1. Lock bolt to rear. Remove magazine. Inspect feed ramp for carbon buildup.
2. Try different magazine. Does it feed now?
3. Check magazine seats fully – does catch click?

Fixed? Yes – If not, continue to Step 2.

Step 2: Range Diagnosis (2 minutes)

1. Cycle slowly by hand. Mark sticking point with Sharpie.
2. Check ejection pattern of previously fired rounds.
3. Try different ammunition.

Likely culprit: Magazine (80%), feed ramp carbon, buffer spring, gas system.

Fixed? Yes – If not, continue to Step 3.

Step 3: Workbench Fix

Magazine fix:

1. Measure feed lip width: should be 0.353″ on USGI. Replace if spread.
2. Replace magazine spring and follower with OEM.

Feed ramp fix:

1. Use brass or nylon brush. Never polish chamber – alters headspace.
2. Apply CLP, brush carbon. Wipe clean.

Buffer fix:

1. Verify carbine vs rifle. Cannot mix carbine buffer with rifle tube.
2. H buffer = 3.0oz standard. H2 = 4.6oz for heavy loads.

Still broken? Escalation path: Find a certified AR armorer.

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Reference Table: All Feeding Issues

Symptom	Likely Cause	Quick Fix
Round jammed on feed ramp	Carbon on ramp, bad mag	Clean ramp, swap mags
Nose dive	Weak spring, spread lips	Replace spring, check 0.353″
Bolt rides over	Slow mag, heavy buffer	Fresh mags, H1 vs H2
Last round only	Weak spring, follower	Replace follower, check BHO
Intermittent	Dirty gas, mixed ammo	Clean gas tube, consistent ammo

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Failure to Fire: Click, No Bang

Symptom: Trigger clicks, hammer falls, but round doesn’t fire.

Step 1: Field Check (30 seconds)

1. Keep muzzle downrange 30 seconds (hangfire check).
2. Eject unfired round. Inspect primer.
3. Try fresh round from different magazine.

Primer strike: Deep dent = bad ammo. Shallow = weak spring. None = FCG issue.

Fixed? Yes – If not, continue to Step 2.

Step 2: Range Diagnosis (2 minutes)

1. Try different ammunition. Steel primers harder than brass.
2. Check hammer spring orientation.
3. Look at spent brass for cratering.

Likely culprit: Ammo, hammer spring, headspace, firing pin.

Fixed? Yes – If not, continue to Step 3.

Step 3: Workbench Fix

Verify chamber: 5.56 NATO, .223 Rem, or .223 Wylde.

Hammer spring:

1. Field strip lower. Remove grip. Drive out trigger pins.
2. Spring orientation: leg on top of trigger bar.
3. Use standard AR-15 hammer spring (6 coils).

Headspace (GO/NO-GO gauges):

1. GO gauge: bolt should close.
2. NO-GO gauge: bolt should NOT close.
3. If NO-GO closes: STOP. Replace barrel.

Still broken? Escalation path: Find a certified AR armorer.

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Reference Table: All Firing Issues

Symptom	Likely Cause	Quick Fix
Click, no primer mark	Hammer not hitting	Check FCG, hammer engagement
Light strike (shallow)	Weak spring, headspace	Replace spring, check headspace
Deep dent, no fire	Bad ammo	Try different ammo
Only with steel	Hard primers	Switch to brass
Intermittent	Worn firing pin	Clean channel, check protrusion

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Failure to Eject: Stovepipe, Brass to Face

Symptom: Spent brass stuck in ejection port, stovepipe, weak ejection.

Step 1: Field Check (30 seconds)

1. Ejection pattern: 3 o’clock = normal, 1 o’clock = overgassed, 4-5 o’clock = undergassed.
2. Is brass dented?
3. Try different ammo.

Fixed? Yes – If not, Step 2.

Step 2: Range Diagnosis (2 minutes)

1. Check extractor tension: should hold bolt weight.
2. Extractor spring should be tight (add O-ring if loose).
3. Ejector should snap back freely.

Fixed? Yes – If not, Step 3.

Step 3: Workbench Fix (Tools required)

Extractor spring: Replace with OEM. Add O-ring.

Chamber: Clean with brass brush. Not steel.

Gas system: Overgassed = heavier buffer. Undergassed = lighter.

Still broken? Find a certified AR armorer.

Reference Table: All Ejection Issues

Symptom	Likely Cause	Quick Fix
Stovepipe	Weak extractor, overgassed, slow bolt	New extractor spring, adjust buffer
Brass to face	Overgassed + weak extractor	O-ring extractor, heavier buffer
3 o’clock ejection	Normal, no action needed	Baseline for comparison
1-2 o’clock ejection	Overgassed	Heavier buffer or adjust gas
4-5 o’clock ejection	Undergassed	Lighter buffer or check gas system

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Failure to Extract: Double Feed

Symptom: Spent casing stays in chamber while new round tries to feed.

Step 1: Field Check (30 seconds)

1. Pull charging handle. Does stuck case extract with force?
2. Look at rim. Gouged = extractor slipped.
3. Try different ammo.

Fixed? Yes – If not, Step 2.

Step 2: Range Diagnosis (2 minutes)

1. Check extractor claw for chip or crack.
2. Check extractor spring tension.
3. Inspect chamber for carbon ring at shoulder.

Fixed? Yes – If not, Step 3.

Step 3: Workbench Fix (Tools required)

Extractor: If chipped/cracked, replace assembly.

Chamber: Clean carbon ring. Do NOT use steel brush.

Headspace: GO closes, NO-GO doesn’t.

Still broken? Find a certified AR armorer.

Reference Table: All Extraction Issues

Symptom	Likely Cause	Quick Fix
Double feed	Extraction failed, case stuck	Replace extractor, clean chamber
Case stuck hard	Carbon ring, gummy chamber, rim tear	Clean chamber, check extractor claw
Rim gouged	Extractor slipping off rim	Replace extractor spring, check claw
Stuck only with steel	Steel doesn’t seal well, more fouling	Clean immediately, may need tuning
Extraction easy but fails	Weak spring, extractor worn	Replace spring/assembly

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Failure to Cycle: Short-Stroking

Symptom: Bolt stops short, won’t go into battery, won’t lock back.

Step 1: Field Check (30 seconds)

1. Manually cycle. Does bolt move freely?
2. Different magazine – does it lock open?
3. Different ammo.

Fixed? Yes – If not, Step 2.

Step 2: Range Diagnosis (2 minutes)

1. Check gas rings: Should support bolt weight on flat surface.
2. Check buffer weight. Standard carbine H = 3.0oz.
3. Gas block alignment: Is port centered?

Fixed? Yes – If not, Step 3.

Step 3: Workbench Fix (Tools required)

Gas rings: Replace if they don’t support bolt weight.

Buffer: Carbine tube = carbine buffer. Rifle tube = rifle buffer.

Gas block: Must align with gas port.

Still broken? Find a certified AR armorer.

Reference Table: All Cycling Issues

Symptom	Likely Cause	Quick Fix
Short-stroking	Heavy buffer, weak gas, light ammo	Verify buffer weight, check gas rings
Won’t lock back	Mag BHO worn, gas leak, weak buffer spring	Check 5,000 round spring length
Won’t go into battery	Dirty bolt carrier, weak spring	Clean carrier, check spring length
Bolt sluggish	Carbon buildup, dry lubrication	Clean rails, relube
Only with steel case	Steel undergassed, needs more gas	Switch to brass or check gas system

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Trigger Won’t Reset

Symptom: Trigger stays dead after firing, no click on next pull.

Step 1: Field Check (30 seconds)

1. Did bolt cycle fully? Short-cycling prevents reset.
2. Release trigger fully forward. Does it re-engage?
3. Pull charging handle 1/4 inch. Does trigger reset now?

Fixed? Yes – If not, Step 2.

Step 2: Range Diagnosis (2 minutes)

1. Field strip lower. Look at trigger housing.
2. Trigger return spring attached? Twisted? Broken?
3. Connector angle: bent or making contact?

Fixed? Yes – If not, Step 3.

Step 3: Workbench Fix (Tools required)

1. Remove trigger housing.
2. Replace return spring OEM. Leg on top of bar.
3. Check connector. If aftermarket, use OEM.
4. Inspect trigger bar for burrs.

Still broken? Find a certified AR armorer.

Reference Table: All Trigger Issues

Symptom	Likely Cause	Quick Fix
Dead trigger after shot	Short-cycling, return spring broken	Fix short-cycle, replace spring
No reset until racked	Return spring detached, connector bent	Check spring, inspect connector
Gritty trigger pull	Debris in FCG, burrs on trigger bar	Clean FCG, inspect for burrs
Aftermarket trigger fails	Aftermarket part tolerance issue	Return to OEM trigger group
Trigger won’t move freely	Hammer spring tension wrong, debris	Check spring orientation

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Magazine Issues

Symptom: One specific magazine causes failures. Won’t seat. Falls out.

Step 1: Field Check (30 seconds)

1. Test with different magazine. Does problem follow the mag?
2. Check for over-insertion or damage to mag catch.
3. Is mag body swollen? Heat + loaded mags = swelling.

Fixed? Yes – If not, Step 2.

Step 2: Range Diagnosis (2 minutes)

1. Disassemble mag. Check follower for damage.
2. Spring should be straight, not kinked.
3. Feed lip width: 0.353″ USGI spec.

Fixed? Yes – If not, Step 3.

Step 3: Workbench Fix (Tools required)

Magazine: Replace spring and follower. OEM preferred.

Body damage: Dents prevent feeding. Dented = replace.

Catch notch: Worn notch won’t hold mag. Replace mag.

Still broken? Find a certified AR armorer.

Reference Table: All Magazine Issues

Symptom	Likely Cause	Quick Fix
Mag won’t seat	Body swollen, notch damage, wrong type	Check body dimensions, try different magazine
Mag falls out	Worn catch, notch grooved, over-insertion	Replace mag, check catch tension
Won’t drop free	Body swollen, debris in mag well	Clean mag well, check mag dimensions
Only one mag causes failures	That magazine is defective	Replace the magazine
Intermittent mag issues	Spring wearing, lips spreading	Replace spring, measure lips 0.353″

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⚠ Time to Call a Pro

Find a certified AR armorer:

• Certified AR Armorers (check manufacturer websites)
• Local gunsmiths with AR-specific experience
• Manufacturer service centers for warranty work

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Extended FAQ: Common Questions Answered

Q: What is the difference between a Failure to Extract and a Failure to Eject?

Failure to Extract: The spent casing is still IN the chamber. The extractor never grabbed it, or grabbed it and lost grip. You see a double feed or racking does not eject.

Failure to Eject: The casing left the chamber but did not clear the gun. Stovepipe, brass to face, or dribbling out.

Why it matters: Different fixes. Extraction = extractor/chamber problem. Ejection = ejector/buffer problem.

Q: My AR-15 runs fine at the range but fails in matches. Why?

Match pressure is real. Three likely culprits:

• Different grip under pressure: Your grip tightens when adrenalized. Practice your shooting stance deliberately.
• Different ammo: Practice with one load, matches with another. Consistency matters.
• Dirty gun: Match day sees more rounds between cleanings. Carbon causes failures.

Q: Can I mix carbine and rifle buffers?

No. Carbine buffer in rifle tube or rifle buffer in carbine tube causes cycling issues.

Component	Carbine System	Rifle System
Buffer	3.0oz standard	5.0oz
Spring length	~10.5″ uncompressed	~13″ uncompressed
Tube length	7.75″ (collapsible)	9.75″ (A2/fixed)

Rule: Match buffer to tube length. Do not mix.

Q: How often should I replace buffer springs?

Usage	Interval	Signs It Is Time
Occasional practice	Every 5,000 rounds / 3-5 years	Short-stroking
Competition	Every 3,000-5,000 rounds	Inconsistent cycling
Suppressed	Every 2,000-3,000 rounds	Faster fatigue

Q: My friend says heavy buffers fix everything. True?

• Overgassed rifle: H2 helps reduce wear
• Undergassed rifle: Heavy buffer makes short-stroking WORSE
• Standard rifle: H buffer (3.0oz) is standard for a reason

My recommendation: Fix the root cause. Heavy buffer is a band-aid, not a cure.

Q: Steel case ammo: yes or no?

• Extractor wear: Steel is harder than brass. Factor replacement cost.
• Harder primers: Light strikes more common.
• Chamber fouling: Clean every session.

Verdict: Practice with brass. Use steel for training cost savings, but clean immediately after.

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Extended FAQ: Common Questions Answered

Q: What is the difference between a Failure to Extract and a Failure to Eject?

Failure to Extract: The spent casing is still IN the chamber. The extractor never grabbed it, or grabbed it and slipped. You see a double feed or racking does not eject.

Failure to Eject: The casing left the chamber but did not clear the gun. Stovepipe, brass to face, or dribbling out the port.

Why it matters: Different fixes. Extraction = extractor/chamber problem. Ejection = ejector/buffer problem.

Q: My AR-15 runs fine at the range but fails in matches. Why?

Match pressure is real. Three likely culprits:

• Limp wrist under pressure: Your grip tightens differently when adrenalized. Practice your shooting stance deliberately.
• Different ammo: You practice with one load, shoot matches with another (especially steel cased). Consistency matters.
• Dirty gun: Match day guns see more rounds between cleanings. Carbon buildup causes intermittent failures.

Q: Can I mix carbine and rifle buffers?

No. Carbine buffer in a rifle tube or rifle buffer in a carbine tube causes cycling issues.

Component	Carbine System (6-position)	Rifle System (A2/Fixed)
Buffer	Carbine length, 3.0oz standard	Rifle length, 5.0oz
Buffer spring	~10.5″ uncompressed	~13″ uncompressed
Tube length	7.75″	9.75″
Buffer weight	H = 3.0oz, H2 = 4.6oz, H3 = 5.3oz	Standard 5.0oz, A5 system variations

Rule: Match buffer to tube. Carbine tube gets carbine buffer. Rifle tube gets rifle buffer.

Q: How often should I replace buffer springs?

Usage	Interval	Signs It is Time
Carbine, occasional practice	Every 5,000 rounds or 3-5 years	Short-stroking, won’t lock back
Competition rifle	Every 3,000-5,000 rounds	Inconsistent ejection, sluggish bolt
Suppressed	Every 2,000-3,000 rounds	More gas = faster spring fatigue
Duty/mil	Annual or per qualification	Preventive maintenance

Measure it: Carbine springs should measure ~10.5″ uncompressed when new. Rifle springs ~13″. Shorter by 1″ or more = replace.

Q: My friend says heavy buffers fix everything. True?

Heavy buffers have their place, but causes and fixes differ:

• Overgassed rifle: H2 or H3 buffer helps tame ejection and reduces wear
• Undergassed rifle: Heavy buffer makes short-stroking WORSE
• Standard rifle: H buffer (3.0oz) is standard for a reason

My recommendation: Fix the root cause. Heavy buffer is a band-aid, not a cure.

Q: Steel case ammo: yes or no?

AR-15s run steel case, but tradeoffs exist:

• Extractor wear: Steel is harder than brass. Extractor hook wears faster. Factored into cost savings.
• Harder primers: Light strikes more common. Check firing pin protrusion.
• Underpowered loads: Some steel case is weaker. Causes more failures to eject and short-stroking.
• Chamber fouling: Bi-metal jackets and sealants leave more residue. Clean chamber every 200 rounds.

Verdict: Practice with brass. Use steel for cost training, but clean the chamber immediately after every session. Factor in extractor replacement cost.

Q: My magazine keeps causing feeding issues. Why?

Three causes:

1. Feed lips spread: USGI spec is 0.353″. Measure with calipers. Replace if over 0.360″.
2. Spring fatigue: 5,000+ rounds on same mag = spring replacement. Or replace entire magazine.
3. Follower tilt: Press rounds down. Follower should stay flat. Tilt means worn or out of spec.

80% rule: If your rifle runs with known-good magazines, the problem is not the rifle. Replace the suspect magazine and move on.

Q: Do I really need to replace parts at round counts, or can I wait until failure?

Service intervals are preventive. Here is the risk assessment:

Component	Run to Failure?	Failure Mode
Buffer spring	Relatively safe	Gun gets sluggish, tells you first
Extractor spring	Moderate risk	Inconsistent ejection, intermittent failures
Hammer spring	High risk	Light strikes when it matters most
Mag springs	Moderate risk	Feed failures, but slow degradation
Gas rings	Do not run to failure	Short-stroke during critical use

Bottom line: Recoil springs can slide. Extractor and hammer springs cannot. Gas rings are cheap insurance.

Q: Wet lube or dry lube?

AR-15s prefer proper lubrication:

• Bolt carrier group: Light CLP on rails. Not dripping, but visible film.
• Firing pin channel: RUN DRY. Oil here collects carbon and causes reliability issues.
• Chamber: Dry. Never lubricate the chamber.
• Buffer tube: Very light lubrication reduces noise and wear.

Q: Extended bolt releases, worth it?

Depends on your use case:

• Left-handed shooters: Ambi releases help without shifting grip
• Competition: Faster reloads, but risk of accidental activation under recoil
• Duty/defense: OEM standard is deliberate. Extended releases risk accidental lock-backs under stress.

My take: If it is a competition-only rifle, extended releases are fine. For duty or defense guns, stick to OEM.

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Quick FAQ

What is the #1 cause of AR-15 malfunctions?

Magazines. 80% of feeding issues are magazine-related. Replace suspect magazines before troubleshooting the rifle.

Can I fix headspace myself?

You can check it with GO/NO-GO gauges. If NO-GO closes, the fix is barrel replacement. That requires an armorer.

Do I need armorers tools for basic maintenance?

No. Roll punches, a bench block, and basic hand tools cover 95% of AR maintenance. Armorers tools are for major work.

When should I clean my AR-15?

Every range trip minimum (bore and chamber). Detailed clean every 500 rounds. Deep inspection every 5,000 rounds.

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Final Thoughts: Confidence Through Competence

Your AR-15 is one of the most customizable and capable rifles you can own, but it is still a machine. Machines wear. Machines fail. The moment you think it is “just an AR, it will run no matter what,” you are gambling.

This guide gives you a blueprint: Symptom to Diagnosis to Fix. No guesswork. No theory. Just what works from decades of working on guns.

Clean your rifle. Replace worn parts. Use quality ammunition. Never ignore small issues.

Because that small stuff? It is what separates a range headache from a real-world failure.

You do not need to be an armorer to keep your AR-15 running. You just need to be someone who gives a damn.

You are. And now, you are armed with the knowledge that proves it.

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Disclaimer

This guide covers standard AR-15/M4 pattern rifles with direct impingement gas systems. Manufacturer-specific variations, piston systems, or proprietary components may require manufacturer-specific documentation. When in doubt, consult a certified AR armorer.

Information accurate as of 5.56 NATO / .223 Remington chambered rifles in 7075-T6 aluminum receivers with standard gas systems.