The TRB Detailed AR-15 Troubleshooting Guide

Your AR-15 was running fine last week. Today it is not. Or worse, it only runs sometimes, which means you cannot trust it yet.

This guide walks you through AR-15 troubleshooting the same way a careful armorer would approach it: start with the simple stuff, isolate one variable at a time, then move to the bench only when the easy checks fail.

The format is simple:

• Step 1: Field Check – A fast check you can do with no special tools.
• Step 2: Range Diagnosis – A controlled test to narrow the cause.
• Step 3: Workbench Fix – The part inspection, service, or replacement path.

Most AR-15 problems come from magazines, ammunition, lubrication, gas system problems, or worn springs. Do not throw parts at the rifle until you know which one is lying to you. Rifles are expensive. Guessing is how the parts bin gets fat.

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Quick Reference Card

Symptom	Quick Check	Most Likely Cause	Start Here
Rounds will not chamber	Swap magazines	Bad magazine, feed lip issue, weak spring	Failure to Feed
Click, no bang	Inspect primer strike	Bad ammo, firing pin issue, hammer spring issue	Failure to Fire
Case stuck in chamber	Check extractor engagement	Dirty chamber, weak extractor, rough chamber, timing issue	Failure to Extract
Case extracts but does not leave the rifle	Check ejector tension	Weak ejector spring, extractor issue, timing issue	Failure to Eject
Bolt does not cycle fully	Check bolt lock-back on empty mag	Under-gassed, gas leak, heavy buffer, weak ammo	Short Stroke / Failure to Cycle
Trigger does not reset	Perform unloaded function check	Trigger spring, disconnector, fire control group issue	Trigger Reset / Hammer Follow
Brass hits your face	Watch ejection pattern	Over-gassed, extractor/ejector timing issue	Failure to Eject
Bolt does not lock back on empty mag	Test with known-good magazine	Magazine spring, under-gassed rifle, heavy buffer	Short Stroke / Failure to Cycle

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Safety Check Before Troubleshooting

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Recommended Tools for This Guide

This troubleshooting guide assumes basic AR-15 maintenance tools. You do not need every tool on the bench for every fix, but these are the tools that keep you from chewing up parts like a raccoon with a socket set.

Tool	Used For	Needed For This Guide?	Approximate Cost
Known-good magazines	Isolating feed and lock-back problems	Yes	$12 to $25 each
Quality factory ammo	Eliminating weak ammo or bad primer variables	Yes	Varies
AR-15 chamber brush	Cleaning chamber and locking lug area	Yes	$5 to $15
Punch set	Extractor, ejector, trigger group, pins	Yes	$10 to $30
Armorer’s wrench	Castle nut, barrel nut, muzzle device work	Sometimes	$20 to $60
Inch-pound torque wrench	Carrier key, optics mounts, small fasteners	Sometimes	$40 to $100
Foot-pound torque wrench	Barrel nut and larger receiver work	Advanced	$40 to $100
Bore light	Inspecting chamber, bore, feed ramps, carbon	Yes	$10 to $30
GO / NO-GO gauges	Checking headspace	Advanced	$60 to $100
Spare extractor kit	Extractor, spring, insert, O-ring if needed	Recommended	$5 to $25

Tools and Parts for This Guide

Workbench Pick

Otis .223/5.56mm Chamber Brush

$4.99 at Palmetto State Armory

Best for: Quick chamber clean during field-stripping. Single-piece bronze brush that reaches the locking lug recess without disassembly.

TRB take: Cheap insurance. A fouled chamber causes more extraction issues than people think. Keep one in your range bag.

Check Price at Palmetto State Armory

Workbench Pick

Wheeler Manual Firearms Accurizing Torque Wrench with Inch/Pounds Measurement, Bits and Storage Case for Scope Mounting, Gunsmithing and Maintenance

ACCURACY: +/- 2 inch/pounds up to 40 inch/pounds; 40 – 65 is +/- 5%. The FAT wrench measures 2 L x 2 W x 6.25 H inches and the storage case measures 7.5 L x 5.5 W x 1.75 H inches

Check Price at Amazon

Workbench Pick

Real Avid Roll Pin Punch Set & Hammer + Non-Slip Magnetic Bench Block | 10 Nickel-Plated Steel Roll Pin Punches, 4 Interchangeable Hammer Heads – Brass, Steel, Ruber, Nylon & Non-Marring Bench Block

Best for: Essential for Glock maintenance and troubleshooting.

TRB take: Magnetic bench block + punch set. Heavy benchwork for trigger housings and detailed work.

Check Price at Amazon

Workbench Pick

PSA AR-15 Extractor Spring Repair Kit

$3.99 at Palmetto State Armory

Best for: Replacing worn extractor springs, O-rings, and inserts on a budget. Everything you need in one bag.

TRB take: For $4, this kit fixes the most common cause of AR extraction failures. PSA's house-brand parts run fine in duty guns.

Check Price at Palmetto State Armory

Workbench Pick

Real Avid Gun Boss Pro Universal – 12 Ga., 20 Ga., .45, .40, .357, .38, 9MM, .30, .280, .270, 7MM, .243, .22 ca. universal gun cleaning kit

Best for: Essential for Glock maintenance and troubleshooting.

TRB take: Compact kit with all basics for field cleaning.

Check Price at Amazon

Workbench Pick

Magpul PMAG 30 AR/M4 Gen M3

$15.99 at GritrSports

Best for: Reliable feeding in any AR-15 platform. Anti-tilt follower, slim profile, and a reputation that earned it military adoption.

TRB take: If you're troubleshooting a feed issue, rule out the magazine first. A Gen M3 PMAG is the gold standard for a reason.

Check Price at GritrSports

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Symptom Selector: Find Your Problem

Pick the symptom that matches your rifle. Start there. Do not start in the middle because your buddy on the internet said “it is always the gas rings.” Your buddy also probably thinks zip ties are a bedding compound.

If This Happens	Possible Cause	Go To Section
Round stays in the magazine or nose-dives into the feed ramps	Magazine, feed lips, follower, feed ramp mismatch	Failure to Feed
Trigger clicks but the round does not fire	Ammo, firing pin, hammer spring, headspace, fire control issue	Failure to Fire
Fired case stays stuck in the chamber	Extractor, dirty chamber, rough chamber, over-gas timing	Failure to Extract
Case pulls out but gets trapped in the action	Ejector spring, extractor tension, gas timing, buffer setup	Failure to Eject
Bolt cycles weakly or does not pick up the next round	Short stroke, gas leak, heavy buffer, weak ammo	Short Stroke / Failure to Cycle
Trigger does not reset after firing	Trigger spring, disconnector, hammer follow, FCG wear	Trigger Reset / Hammer Follow
Brass hits your face or ejects forward hard	Over-gassed rifle, early unlock, extractor/ejector timing	Failure to Eject
Bolt does not lock back after last round	Magazine follower, weak mag spring, under-gas, heavy buffer	Short Stroke / Failure to Cycle

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Failure to Feed: When Rounds Will Not Chamber

Why it happens: Failure to feed usually starts with magazine presentation. The magazine controls the angle, height, and timing of the next round. If the magazine is wrong, the rifle is already losing before the bolt starts moving.

Step 1: Field Check

Goal: Rule out the magazine and obvious feed path problems.

Tools: None, but a known-good magazine helps.

Time: 30 seconds.

• Clear the rifle. Remove the magazine, lock the bolt to the rear, and verify the chamber is empty.
• Inspect the magazine. Look for cracked feed lips, spread feed lips, dents, debris, or a follower that tilts or binds.
• Press the follower down. It should move smoothly and return with steady spring pressure.
• Try a known-good magazine. If the problem disappears, mark the bad magazine and remove it from serious use.
• Check the top round angle. The round should sit nose-up slightly and point toward the chamber, not straight into the receiver wall.

Fixed? If a magazine swap fixes the problem, keep the good magazine and retire or mark the bad one as range-only.

Not fixed? Move to Step 2.

Step 2: Range Diagnosis

Goal: Separate magazine, ammo, feed ramp, and bolt velocity problems.

Tools: Three magazines, two ammo types, safe range setup.

• Magazine swap test: Test three different magazines if possible. Use PMAG, USGI aluminum, Lancer, or another known-good brand.
• Ammo test: Try quality brass-cased factory ammunition. Some rifles dislike certain bullet profiles or long overall lengths.
• Hand-cycle test: With dummy rounds or at the range using safe procedures, cycle the rifle briskly. Do not ride the charging handle.
• Feed ramp inspection: Look for a visible ledge where the barrel extension ramps meet the upper receiver ramps.
• Bolt velocity clue: If the rifle feeds when hand-cycled but fails during live fire, the problem may be short-stroking rather than feed geometry.

Fixed? If one magazine or ammo type causes the failure, you found the variable.

Not fixed? Move to Step 3.

Step 3: Workbench Fix

Goal: Inspect parts that control round presentation and bolt movement.

Tools Needed:

• Known-good magazines
• Bore light
• Chamber brush
• Calipers if checking feed lips
• Fine stone only for minor burr removal

• Replace suspect magazines. Do not try to “tune” cracked or badly spread feed lips for serious use.
• Inspect the follower and spring. Replace weak magazine springs or upgrade old followers if the magazine body is still good.
• Inspect the bolt face. Look for burrs on the lower edge where the bolt strips rounds from the magazine.
• Remove only obvious burrs. Do not reshape the bolt or feed ramps.
• Check the gas system if bolt velocity seems weak. See the Short Stroke / Failure to Cycle section.

Symptom	Likely Cause	How to Confirm	Fix	Skill Level
Round nose-dives into feed ramp	Weak magazine spring or follower tilt	Fails with one magazine only	Replace spring, follower, or magazine	Beginner
Bolt rides over top round	Magazine sits low, weak mag spring, low bolt velocity	Compare known-good magazine and live-fire cycling	Replace magazine or diagnose short stroke	Beginner
Round jams at feed ramp	Feed ramp burr, ammo profile, magazine presentation	Inspect ramps and test different ammo	Remove minor burrs or use gunsmith for ramp correction	Intermediate
Fails only during live fire	Short stroke or gas issue	Hand-cycles fine but fails under fire	Diagnose gas, buffer, ammo, and magazines	Intermediate

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Failure to Fire: Click, No Bang

Why it happens: Failure to fire usually comes from ammunition, firing pin movement, hammer spring energy, fire control group issues, or headspace problems. Primer marks tell the story. Read them before replacing parts.

Step 1: Field Check

Goal: Determine whether the round, firing pin, or hammer system failed.

Tools: None.

Time: 30 seconds.

• Keep the muzzle pointed downrange. If the rifle went click instead of bang, wait 60 seconds before opening the action in case of delayed ignition.
• If the shot sounded weak, stop immediately. Do not chamber another round until you inspect the bore for obstruction.
• Clear the rifle. Remove the magazine, lock the bolt back, and inspect the chamber.
• Inspect the primer. Look for no strike, light strike, off-center strike, or a normal deep strike.
• No primer mark: The firing pin may not have reached the primer, or the hammer may not have fallen correctly.
• Light primer mark: Possible weak hammer spring, firing pin drag, carbon buildup, hard primer, or headspace issue.
• Normal primer mark: Suspect bad ammunition first.

Fixed? If one round failed but the rifle runs normally with other ammo, document the ammo lot and move on.

Not fixed? Move to Step 2.

Step 2: Range Diagnosis

Goal: Separate ammo failure from rifle failure.

Tools: Quality factory ammunition, safe range setup.

• Ammo isolation test: Fire five rounds from a different manufacturer or lot.
• Hard-primer clue: If only one ammo type fails, that ammo may have hard primers or poor quality control.
• Firing pin protrusion check: Field strip the bolt carrier group and push the firing pin forward. It should protrude through the bolt face. If it does not, inspect for carbon, damage, or obstruction.
• Hammer spring feel: With the upper removed and the lower clear, cock the hammer carefully. Weak or mushy hammer tension can point to a reversed or worn spring.
• Function check: Perform a safe unloaded function check. If the hammer follows the bolt or fails to stay cocked, go to Trigger Reset / Hammer Follow.

Fixed? If fresh ammo solves it, log the bad ammo and keep it out of serious use.

Not fixed? Move to Step 3.

Step 3: Workbench Fix

Goal: Inspect the ignition path from hammer to primer.

Tools Needed:

• Punch set
• Cleaning solvent
• Replacement firing pin
• Replacement hammer spring
• GO / NO-GO gauges if headspace is suspected

• Clean the firing pin channel. Carbon drag can slow the firing pin, especially when the rifle is hot.
• Inspect the firing pin. Replace it if it is bent, cracked, heavily worn, mushroomed, or damaged.
• Inspect hammer spring orientation. The spring legs should rest correctly on the trigger pin. Reversed hammer springs are a common cause of light strikes.
• Replace weak springs. Springs are cheap. Mystery failures are not.
• Check headspace if light strikes persist. GO should close. NO-GO should not close. If results are unclear, stop and use a qualified armorer.

Symptom	Likely Cause	How to Confirm	Fix	Skill Level
No primer mark	Broken firing pin, obstructed firing pin path, hammer did not fall	Inspect firing pin and perform function check	Clean channel, replace firing pin, inspect FCG	Beginner to Intermediate
Light primer strike	Weak hammer spring, firing pin drag, hard primers	Test with different ammo and inspect spring orientation	Replace spring, clean firing pin channel	Beginner
Normal primer strike, no ignition	Bad ammunition	Repeat with different ammo lot	Stop using that ammo for serious use	Beginner
Hammer follows bolt	Disconnector or fire control group issue	Unloaded function check fails	Replace damaged FCG parts or complete trigger group	Intermediate

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Failure to Extract: Case Stuck in Chamber

Why it happens: Failure to extract usually comes from weak extractor tension, a dirty chamber, sticky ammunition, rough chamber walls, or timing problems where the rifle starts extraction while chamber pressure is still high.

Step 1: Field Check

Goal: Clear the rifle safely and identify whether the extractor is gripping the case.

Tools: None.

Time: 30 seconds, unless the case is stuck hard.

• Keep the muzzle pointed in a safe direction.
• Remove the magazine. Do not add another round to a rifle that already has a stuck case problem.
• Inspect through the ejection port. Look for the case rim and bolt position.
• Do not force the charging handle. If the bolt is partially open and a live round may be involved, stop and handle it as a serious safety issue.
• Check extractor engagement. If the extractor is over the rim but cannot pull the case, suspect a sticky chamber, rough chamber, or pressure/timing issue.
• Check rim damage. Torn or chewed rims point toward extraction force problems or chamber drag.

Fixed? If the case clears and the extractor passes a basic grip check, clean the chamber and test carefully.

Not fixed? Move to Step 2 after the rifle is safely cleared.

Step 2: Range Diagnosis

Goal: Separate dirty chamber, ammo, extractor, and gas timing problems.

Tools: Known-good brass-cased ammo, chamber brush, bore light.

• Chamber carbon check: Inspect the chamber with a bore light. Heavy carbon can look like dark varnish and can increase case drag.
• Clean the chamber. Use a proper AR-15 chamber brush. Brass or nylon only.
• Ammo isolation test: Test with quality brass-cased factory ammo. If problems only happen with steel-cased ammo, clean the chamber and treat that ammo as a variable.
• Look at ejection pattern. Forward ejection and brass to face can suggest over-gas or early unlock. Weak rearward ejection can suggest low bolt velocity.
• Extractor tension test: Remove the bolt. Slip a spent case under the extractor. The extractor should hold the case firmly against the bolt face.

Fixed? If cleaning the chamber or changing ammo solves it, log the result.

Not fixed? Move to Step 3.

Step 3: Workbench Fix

Goal: Service the extractor and chamber without damaging safety-critical surfaces.

Tools Needed:

• Chamber brush
• Carbon remover
• Punch set
• Extractor spring kit
• Replacement extractor if needed
• Bore light

• Deep clean the chamber. Use solvent and a chamber brush until patches come out clean.
• Do not polish the chamber with abrasive tools. Chamber dimensions matter. This is not the place for “close enough.”
• Inspect the extractor hook. Look for chips, rounding, cracks, or heavy wear.
• Replace the extractor spring. If tension is weak, replace the spring and insert.
• Test an O-ring carefully. Some extractor setups benefit from an O-ring. Some do not. Test reliability before trusting it.
• Check for over-gas. If extraction is violent, rims are damaged, and brass ejects forward, consider buffer weight or gas tuning.
• Inspect the chamber. Pitting, scratches, roughness, or corrosion require professional attention.

Symptom	Likely Cause	How to Confirm	Fix	Skill Level
Extractor slips over rim	Weak extractor spring or worn extractor hook	Spent case grip test fails	Replace extractor spring or extractor	Beginner
Extractor tears case rim	Sticky chamber, rough chamber, early unlock	Inspect chamber and ejection pattern	Clean chamber, inspect extractor, evaluate gas timing	Intermediate
Only fails with steel-cased ammo	Ammo/chamber friction variable	Runs with brass but not steel	Clean chamber and use ammo the rifle runs reliably	Beginner
Cases remain stuck after cleaning	Rough or damaged chamber	Bore light shows scratches, pitting, or roughness	Gunsmith inspection	Professional

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Failure to Eject: Stovepipes, Trapped Brass, and Brass to Face

Why it happens: Ejection depends on extraction grip, ejector spring force, bolt speed, and timing. If one of those is off, the spent case does something stupid. It is brass. It has no ambition.

Step 1: Field Check

Goal: Rule out debris, weak ejector movement, and extractor grip.

Tools: None.

Time: 30 seconds.

• Clear the rifle. Remove the magazine and verify the chamber is empty.
• Inspect the ejection port. Look for carbon, brass shavings, debris, or damage.
• Check the brass deflector. Look for sharp burrs or unusual wear patterns.
• Press the ejector. With the bolt removed, the ejector should move under firm spring pressure and return quickly.
• Check extractor grip. A spent case should stay held under the extractor when the bolt is gently shaken.

Fixed? If debris or a simple extractor issue was corrected, test carefully.

Not fixed? Move to Step 2.

Step 2: Range Diagnosis

Goal: Use ejection pattern and live-fire behavior to identify timing, gas, buffer, ammo, or spring problems.

Tools: Safe range setup, known-good magazines, quality ammo.

• Fire five slow rounds. Watch where the brass lands.
• Fire five controlled rapid rounds. Watch whether the ejection pattern changes.
• Use known-good brass-cased ammo. Weak or inconsistent ammo can muddy the diagnosis.
• Test with a known-good magazine. Feeding and bolt velocity problems can look like ejection problems.
• Watch the pattern:
  • 1 to 2 o’clock: Often points to over-gas or early unlock, but confirm with recoil feel, brass condition, buffer setup, ammo, and reliability.
  • 3 to 4 o’clock: Commonly treated as a healthy ejection range when the rifle is otherwise running reliably.
  • 5 to 6 o’clock: Can point to under-gas, weak ammo, heavy buffer, or low bolt speed.
  • Stovepipe: Often means the case did not clear before the bolt returned.

Fixed? If ammo, magazine, or buffer changes solve the issue, log it.

Not fixed? Move to Step 3.

Step 3: Workbench Fix

Goal: Inspect ejector, extractor, gas, and buffer timing.

Tools Needed:

• Punch set
• Bolt support tool if available
• Replacement ejector spring
• Replacement extractor spring kit
• Cleaning solvent
• Bore light

• Inspect ejector movement. The ejector should move smoothly and return with authority.
• Replace the ejector spring if weak. A weak ejector spring can cause cases to dribble, stovepipe, or stay trapped.
• Inspect the ejector pin. Look for peening, bending, or damage.
• Inspect extractor condition. Ejection begins with the extractor holding the case correctly.
• Check gas rings. If the carrier drops under its own weight during the gas ring test, replace the rings.
• Review buffer weight. Over-gassed rifles may benefit from a heavier buffer. Under-gassed rifles may not tolerate one.
• Inspect the chamber. Sticky extraction can cause weak or inconsistent ejection.

Symptom	Likely Cause	How to Confirm	Fix	Skill Level
Brass to face	Over-gas, early unlock, extractor/ejector timing	Forward ejection and harsh cycling	Inspect extractor/ejector, consider buffer or gas tuning	Intermediate
Stovepipe	Weak ejection, low bolt speed, timing issue	Case trapped vertically in ejection port	Check ejector spring, ammo, gas, buffer	Beginner to Intermediate
Case extracts but falls inside action	Weak ejector spring	Ejector feels weak or slow	Replace ejector spring	Intermediate
Erratic ejection pattern	Ammo variation, gas issue, extractor/ejector inconsistency	Pattern changes round to round	Test known-good ammo, inspect BCG parts	Intermediate

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Short Stroke / Failure to Cycle

Why it happens: Short stroking means the bolt carrier group is not getting enough energy to complete the cycle. Common causes include gas leaks, gas block misalignment, weak ammo, excessive buffer weight, dirty chamber, worn gas rings, or a loose carrier key.

Step 1: Field Check

Goal: Find obvious gas, buffer, magazine, and lubrication problems.

Tools: None.

Time: 30 seconds.

• Clear the rifle.
• Check lubrication. A dry AR-15 can act under-gassed. Lube the bolt carrier rails, cam pin area, bolt, and gas rings.
• Check the magazine. Use a known-good magazine for lock-back testing.
• Check buffer marking. H2 or H3 buffers can be too heavy for some setups, especially with weaker ammo.
• Look for gas leaks. Heavy carbon around the gas block, gas tube, or carrier key can point toward leakage.
• Check carrier key movement. If the carrier key moves, stop. That rifle is not ready to fire.

Fixed? If lubrication, magazine, or buffer correction solves it, test and log the change.

Not fixed? Move to Step 2.

Step 2: Range Diagnosis

Goal: Confirm short stroke and isolate ammo, magazine, gas, or buffer causes.

Tools: One known-good magazine, quality 5.56 ammo if appropriate for the barrel, safe range setup.

• One-round lock-back test: Load one round in a known-good magazine. Fire. The bolt should lock back on the empty magazine.
• If it does not lock back: Suspect low bolt travel from gas, ammo, buffer, friction, or magazine follower issues.
• Repeat with another magazine. This eliminates a weak follower or magazine spring.
• Repeat with stronger factory ammo. Weak .223 loads can cause cycling issues in some rifles.
• Watch ejection:
  • 3 to 4 o’clock: Generally healthy.
  • 5 to 6 o’clock or weak dribble: Possible low bolt velocity.
  • 1 to 2 o’clock with harsh recoil: May be over-gas or early unlock, not true under-gas.

Fixed? If ammo or magazine changes solve it, document the working setup.

Not fixed? Move to Step 3.

Step 3: Workbench Fix

Goal: Inspect the gas system and moving parts.

Tools Needed:

• Bore light
• Punch set
• Gas ring set
• Armorer’s tools if removing the gas block
• Torque wrench if servicing carrier key or gas block screws

• Check gas rings. Extend the bolt and stand the carrier group on the bolt face. If the carrier collapses under its own weight, replace the rings.

Staggering gas ring gaps during assembly is common practice, but the important field check is whether the rings still seal well enough to pass the support test.

• Inspect carrier key staking. The key screws should be tight and properly staked. If loose, stop and repair correctly.
• Inspect gas tube alignment. The gas tube should enter the carrier key smoothly without binding.
• Inspect gas block alignment. Misalignment can partially block the barrel gas port.
• Inspect for carbon leaks. Some carbon staining is normal, but heavy leakage can signal poor fit.
• Clean the chamber. Chamber drag can steal cycling energy.
• Evaluate buffer weight. If the rifle is under-gassed or ammo is weak, excessive buffer weight can make cycling worse.

Symptom	Likely Cause	How to Confirm	Fix	Skill Level
No lock-back on empty mag	Low bolt travel, mag issue, gas issue	One-round lock-back test	Test magazine, ammo, gas, buffer	Beginner
Weak ejection	Low bolt speed, gas leak, weak ammo	Cases land rearward or barely clear rifle	Inspect gas system, ammo, buffer	Intermediate
Carrier key loose	Gas loss at carrier key	Key moves or staking is poor	Properly torque and stake or replace BCG	Intermediate
Fails after several magazines	Heat, carbon, friction, lubrication issue	Runs clean, fails dirty/hot	Clean, lube, inspect chamber and gas rings	Beginner
Fails with heavy buffer only	Buffer too heavy for setup	Runs with lighter buffer	Use correct buffer for gas/ammo setup	Beginner

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Trigger Reset / Hammer Follow

Why it happens: Trigger reset and hammer follow problems come from the fire control group. Common causes include reversed springs, weak springs, worn disconnector engagement, rough parts, damaged pins, or poorly fitted aftermarket triggers.

Step 1: Field Check

Goal: Determine whether the trigger resets safely.

Tools: None.

Time: 30 seconds.

Perform this check only with the rifle unloaded.

• Remove the magazine.
• Verify the chamber is empty.
• Point the rifle in a safe direction.
• Charge the rifle to cock the hammer.
• Place the selector on SAFE and press the trigger. The hammer must not fall.
• Move selector to FIRE and press the trigger. The hammer should fall.
• Hold the trigger to the rear.
• Cycle the charging handle.
• Slowly release the trigger. You should feel and hear a reset click.
• Press the trigger again. The hammer should fall normally.

Fixed? If the rifle passes repeatedly and the issue does not return, document it and continue testing cautiously.

Not fixed? Move to Step 2. If the hammer falls on SAFE or follows the bolt, stop using the rifle.

Step 2: Range Diagnosis

Goal: Separate reset failure, hammer follow, and short-stroke symptoms.

Tools: Safe range setup, known-good ammo.

• Load one round. Fire and hold the trigger to the rear through recoil.
• Release slowly. Listen and feel for reset.
• Load two rounds. Fire one round, hold the trigger, release, then fire the second.
• Watch hammer behavior. If the hammer ends up down or at half-cock without a proper trigger press, suspect hammer follow.
• Do not continue rapid fire testing if hammer follow appears. This is not a “maybe it will wear in” problem.

Failure Type	Hammer Position	Trigger Feel	Likely Cause
Reset failure	Hammer cocked	Trigger dead or will not reset	Trigger spring, disconnector timing, trigger drag
Hammer follow	Hammer forward or half-cock	May feel normal before failure	Disconnector, sear engagement, worn FCG parts
Light strike after cycling	Hammer may have followed bolt	Inconsistent	Hammer follow or weak hammer spring
Gritty reset	Usually cocked	Grinding or rough reset	Rough engagement surfaces, debris, poor trigger fit

Fixed? If cleaning and correct spring installation resolve the issue and the rifle passes function checks, test cautiously.

Not fixed? Move to Step 3.

Step 3: Workbench Fix

Goal: Inspect or replace the fire control group safely.

Tools Needed:

• Punch set
• Non-marring hammer
• Cleaning solvent
• Light grease
• Replacement trigger spring
• Replacement hammer spring
• Replacement disconnector or complete fire control group

• Inspect spring orientation. Trigger and hammer springs installed backward can cause weak reset or light strikes.
• Inspect the disconnector. Look for chips, cracks, rounding, or modified geometry.
• Inspect hammer and trigger engagement surfaces. Do not reshape engagement surfaces.
• Clean the FCG. Dirt, brass shavings, and old lube can cause drag.
• Replace questionable parts. If disconnector geometry is worn or altered, replace it.
• Consider replacing the complete FCG. If multiple parts are suspect, a known-good mil-spec trigger group is often the cleanest fix.
• Function check repeatedly before live fire. The rifle must pass safe, fire, reset, and hammer retention checks every time.

Part	Failure Sign	Fix	Estimated Cost	Keep Spare?
Trigger spring	Trigger does not return or reset	Reinstall correctly or replace	$3 to $8	Yes
Hammer spring	Light strikes, weak hammer force	Reinstall correctly or replace	$3 to $10	Yes
Disconnector spring	Hammer follow or inconsistent reset	Replace spring	$2 to $5	Yes
Disconnector	Rounded hook, chips, hammer follow	Replace	$10 to $25	Recommended
Complete FCG	Multiple worn or unknown parts	Replace complete group	$35 to $100+	Optional

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Maintenance Schedule: Keep the Rifle Running

Troubleshooting is easier when maintenance is boring. The goal is to catch wear before it becomes a malfunction.

Interval	What to Inspect	What to Replace	Notes
After every range session	Chamber, bore, bolt carrier group, lubrication	Nothing unless damaged	Wipe carbon, clean chamber, relube
Every 500 rounds	Extractor tension, gas rings, bolt lugs, cam pin	Damaged small parts	Good interval for a BCG deep clean
Every 1,000 rounds	Buffer spring, buffer face, carrier key, gas tube fit	Questionable springs or damaged parts	Check for unusual wear patterns
Every 3,000 rounds	Extractor spring, ejector movement, fire control group	Extractor spring if reliability matters	Defensive rifles should get conservative service
Every 5,000 rounds	Ejector spring, gas rings, cam pin, bolt lugs	Worn springs and rings	Good time for a reliability refresh

Authority Forge product card insertion point: Add maintenance product cards here for extractor spring kit, gas rings, chamber brush, lubricant, and magazines.

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AR-15 Wear Parts Replacement Schedule

These are conservative inspection and replacement guidelines, not magic expiration dates. Suppressed use, heat, high round counts, poor ammo, and hard firing schedules can shorten part life.

Part	Conservative Inspection Point	Common Failure Sign	Estimated Cost	Keep Spare?
Extractor spring	3,000 to 5,000 rounds	Rim slip, extraction issues	$3 to $8	Yes
Ejector spring	5,000 to 7,000 rounds	Weak ejection, stovepipes, brass to face	$2 to $8	Yes
Gas rings	When cycling weakens or during BCG inspection	Carrier fails gas ring support test	$3 to $10	Yes
Buffer spring	10,000 rounds or if cycling changes	Sluggish return, inconsistent cycling	$10 to $25	Recommended
Firing pin	During BCG inspection	Light strikes, tip damage, bending	$10 to $25	Yes
Cam pin	Every 1,000 rounds	Peening, cracks, heavy wear	$5 to $15	Yes
Bolt	Regularly after high round counts	Cracked lugs, cam pin hole wear	$60 to $150	Optional
Magazines	Every range session	Feed problems, cracks, weak spring	$12 to $25	Yes

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Problem Solved: What to Do After the Fix

Once the rifle runs again, do not immediately declare victory and trust it. Confirm the fix.

• Log the issue. Write down date, round count, ammo, magazine, malfunction, and fix.
• Change one variable at a time. If you swap ammo, magazine, buffer, and extractor all at once, you will not know what fixed it.
• Test with known-good magazines. Use the magazines you actually plan to trust.
• Test with the ammo you plan to use. Training ammo and defensive ammo can behave differently.
• Run a confirmation test. A serious-use rifle should run more than one perfect magazine before you trust the repair.
• Inspect related parts. If the extractor failed, inspect the bolt. If the gas rings failed, inspect the carrier and key.

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Extended FAQ

Why does my AR-15 fail only when it gets hot?

Heat changes clearances, burns off lubrication, and makes carbon buildup more noticeable. Check the chamber, extractor, firing pin channel, and lubrication first. If the rifle runs cold but fails hot, look for friction, chamber drag, carbon buildup, or timing issues.

Why won’t my AR-15 cycle?

Start with the one-round lock-back test. If the bolt does not lock back on an empty known-good magazine, check ammo, gas block alignment, gas leaks, buffer weight, gas rings, carrier key staking, and lubrication.

What does my AR-15 ejection pattern mean?

Ejection pattern is a diagnostic clue. Brass around 3 to 4 o’clock is generally healthy. Brass forward around 1 to 2 o’clock often suggests over-gas or early unlock. Brass weakly falling rearward can suggest low bolt velocity, under-gas, weak ammo, or excessive buffer weight. Use ejection pattern with other evidence.

Why does my AR-15 click but not fire?

Inspect the primer. No primer mark points toward firing pin or hammer movement problems. A light mark suggests weak hammer energy, firing pin drag, hard primers, or headspace concerns. A normal primer strike usually points toward bad ammunition.

Why does my AR-15 run with brass but fail with steel-cased ammo?

Steel-cased ammo can extract differently and may expose chamber, extractor, or timing problems. Clean the chamber thoroughly, inspect extractor tension, then retest with brass-cased factory ammo. If the rifle only fails with one ammo type, treat that ammo as the variable.

Do I need an adjustable gas block?

Most AR-15 owners do not need one. Adjustable gas blocks are useful for tuning suppressed rifles, competition rifles, or unusual setups. For defensive rifles, simplicity matters. A fixed gas block that runs reliably is hard to beat.

Why does my bolt not lock back on an empty magazine?

Check the magazine first. A weak magazine spring or follower problem can prevent lock-back. If multiple known-good magazines fail, run the one-round lock-back test and inspect gas, buffer, ammo, and bolt catch function.

How often should I clean my AR-15?

Clean and relube after each range session if the rifle is used for serious purposes. At minimum, keep the chamber, bolt carrier group, extractor area, and carrier rails clean and lubricated. A dirty AR can run. A dry, dirty AR is where the comedy starts.

Should I polish my AR-15 trigger?

Do not reshape trigger engagement surfaces unless you truly know what you are doing. Changing geometry can create hammer follow or unsafe function. Clean the fire control group, lightly lubricate where appropriate, and replace rough parts if needed.

Can I convert a 5.56 AR-15 to 300 Blackout by changing the barrel?

Mechanically, many conversions center around the barrel and gas setup, but the safety issue is ammunition management. 300 BLK can chamber in a 5.56 barrel and create catastrophic pressure. If you run both calibers, use dedicated, clearly marked magazines and strict storage separation.

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Quick FAQ

Why won’t my AR-15 feed?

Start with the magazine. Test a known-good magazine and quality factory ammo before inspecting feed ramps or gas issues.

Why does my AR-15 fail to extract?

Check chamber cleanliness and extractor tension first. Dirty chambers and weak extractor springs are common causes.

Why is brass hitting me in the face?

Brass to face often points toward over-gas, early unlock, or extractor/ejector timing issues. Watch ejection pattern and inspect extractor and ejector springs.

What buffer weight should I use?

Use the buffer that lets your rifle cycle reliably with your gas system and ammunition. Heavier buffers can calm over-gassed rifles, but they can make under-gassed rifles worse.

What spare AR-15 parts should I keep?

Keep an extractor spring kit, firing pin, cam pin, gas rings, ejector spring, and known-good magazines.

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Final Thoughts: Confidence Through Competence

The AR-15 is easy to work on compared to many rifles, but easy does not mean maintenance-free.

It still needs clean magazines, good ammo, lubrication, working springs, proper gas flow, and a fire control group that passes safety checks every time.

The troubleshooting path is simple:

• Identify the symptom.
• Check the simple stuff first.
• Change one variable at a time.
• Confirm the fix before trusting the rifle.
• Stop when the problem becomes safety-critical.

You do not need to be an armorer to keep an AR-15 running. You need a process. This guide gives you that process.

Run the rifle. Log the data. Replace worn parts before they ruin the day. And when the rifle starts telling you something is wrong, listen before it starts yelling.

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Disclaimer

You are responsible for your own safety and firearm function. Improper firearm repair can cause injury, death, or property damage. This guide covers common AR-15 troubleshooting steps and general maintenance concepts, but every rifle and manufacturer specification may vary.

• Verify the rifle is unloaded before inspection or maintenance.
• Use the correct tools.
• Follow manufacturer specifications.
• Use proper torque values where required.
• Check headspace when appropriate.
• Test repairs safely before trusting the rifle.
• Use a qualified armorer or gunsmith when a repair is beyond your skill level.

This guide is a diagnostic workflow, not a substitute for professional judgment. If something feels wrong, stop and verify it.