Question 1

What Gas System Length Do I Need for a 16-Inch AR-15 Barrel?

Accepted Answer

A mid-length gas system is the best choice for a 16-inch AR-15 barrel. It provides approximately 7 inches of dwell time, resulting in smooth, reliable cycling with manageable recoil and longer component life compared to carbine-length gas.

Question 2

What Size Should the Gas Port Be on My AR-15 Barrel?

Accepted Answer

Gas port size depends on both barrel length and gas system length. For a typical 16-inch mid-length barrel, the gas port should be 0.070 to 0.073 inches. Shorter barrels with carbine gas typically need 0.078 to 0.093 inches, while rifle-length systems on 18- to 20-inch barrels use 0.086 to 0.093 inc

Question 3

Should I Use an Adjustable or Fixed Gas Block on My AR-15?

Accepted Answer

Use an adjustable gas block if you shoot suppressed, run multiple ammunition types, or want to fine-tune your rifle's cycling. A fixed (non-adjustable) gas block is simpler, more reliable for duty or defensive rifles, and requires no tuning. For most first-time builders shooting unsuppressed with br

Question 4

How Do I Know If My AR-15 Is Over-Gassed or Under-Gassed?

Accepted Answer

An over-gassed AR-15 ejects brass violently at the 1 to 2 o'clock position, has harsh felt recoil, and may show signs of accelerated bolt carrier group wear. An under-gassed AR-15 fails to lock the bolt back on an empty magazine, short strokes, experiences failures to eject, or has inconsistent cycl

Question 5

What Gas Tube Length and Material Do I Need for My AR-15?

Accepted Answer

Gas tube length must match your gas system: pistol (6.75 inches), carbine (9.75 inches), mid-length (11.75 inches), or rifle (15.125 inches). Standard gas tubes are made of 304 stainless steel, which handles the heat and corrosive gas environment well. There is no practical reason to use a different

Question 6

How Do I Tune My AR-15 Gas System for a Suppressor?

Accepted Answer

Install an adjustable gas block and increase buffer weight. Suppressors add significant back pressure that overgasses most AR-15s. Start by closing the adjustable gas block, then open it incrementally until the rifle cycles reliably both suppressed and unsuppressed. An H2 or H3 buffer paired with an

Question 7

When Should I Use a Pistol-Length Gas System on My AR-15?

Accepted Answer

Use a pistol-length gas system on AR-15 barrels between 4 and 10 inches. It is the only gas system that provides enough dwell time on very short barrels to cycle the action reliably. Barrels 10.5 inches and longer should use carbine-length or longer gas systems instead.

Question 8

What Barrel Nut Thread Pattern Does My AR-15 Upper Receiver Use?

Accepted Answer

Standard AR-15 upper receivers use 1-3/16 x 16 TPI (threads per inch) barrel nut threads. This is a universal military specification thread pattern shared by virtually all AR-15 upper receivers, meaning any mil-spec barrel nut will fit any standard AR-15 upper. AR-10 and large-frame receivers use a

Question 9

Can I Use the Same Bolt Carrier Group for Different AR-15 Calibers?

Accepted Answer

No, not always. A standard 5.56 NATO bolt carrier group works for 5.56, .223 Remington, .223 Wylde, and 300 Blackout because they share the same bolt face diameter. However, calibers like 6.5 Grendel, 6.8 SPC, 7.62x39, and .450 Bushmaster require caliber-specific bolts with different bolt face dimen

Question 10

What Are the Different AR-15 Handguard Mounting Systems?

Accepted Answer

The three main AR-15 handguard mounting systems are drop-in (two-piece) handguards that attach to the delta ring and front sight base, free-float handguards that mount directly to a proprietary barrel nut, and M-LOK or KeyMod attachment systems for mounting accessories to free-float rails. M-LOK has

Question 11

What Buffer Weight Should I Use for My AR-15 Build?

Accepted Answer

Start with a standard carbine buffer (3.0 oz) for most builds. Move to an H buffer (3.8 oz) if your rifle is slightly overgassed. Use an H2 buffer (4.6 oz) for suppressed builds or barrels with oversized gas ports. H3 buffers (5.4 oz) are for heavily overgassed or suppressed short-barreled rifles. R

Question 12

Will Any AR-15 Upper Fit Any AR-15 Lower Receiver?

Accepted Answer

Yes, any mil-spec AR-15 upper receiver will fit any mil-spec AR-15 lower receiver. The takedown pin and pivot pin dimensions are standardized across manufacturers. However, fitment tightness varies, some combinations will be tight, others may have slight wobble. AR-15 uppers will NOT fit AR-10 lower

Question 13

What Thread Pitch Does My AR-15 Muzzle Use for Muzzle Devices?

Accepted Answer

Standard AR-15 barrels in 5.56 NATO and .223 Remington use 1/2 x 28 TPI (threads per inch) muzzle threads. AR-10 barrels in .308 Winchester and 7.62 NATO use 5/8 x 24 TPI. Other calibers vary, always verify your barrel's thread pitch before purchasing a muzzle device.

Question 14

Are AR-15 Triggers Universal? Will Any Trigger Fit My Lower?

Accepted Answer

Yes, virtually all AR-15 triggers are compatible with any mil-spec AR-15 lower receiver. The trigger, hammer, and disconnector use standardized pin sizes (0.154-inch mil-spec or 0.170-inch large pin) and standardized pocket dimensions. The only compatibility concern is matching your trigger to your

Question 15

Why Is My AR-15 Failing to Eject? How Do I Fix Stovepipes?

Accepted Answer

The most common causes of failure to eject (stovepipes) are a weak or broken extractor spring, insufficient gas (undergassed), a dirty chamber or bolt, and a worn ejector or ejector spring. Start by cleaning the bolt and chamber thoroughly, then inspect the extractor spring tension and check gas blo

Question 16

My AR-15 Is Short Stroking, What Should I Check and Fix?

Accepted Answer

Short stroking means the bolt carrier is not traveling far enough rearward to pick up the next round or lock back on empty. The most common causes are gas block misalignment, a gas key that is not properly torqued or staked, a buffer that is too heavy, carbon buildup in the gas system, and an unders

Question 17

What Causes Light Primer Strikes on My AR-15?

Accepted Answer

Light primer strikes are most commonly caused by the hammer spring being installed incorrectly (legs under the trigger pin instead of over it), a dirty or obstructed firing pin channel, hard primers on certain ammunition, a worn or short firing pin, or the bolt not being fully in battery when the ha

Question 18

Why Is My AR-15 Double Feeding? How Do I Fix It?

Accepted Answer

Double feeds occur when two rounds try to enter the chamber simultaneously. The most common causes are a worn or damaged extractor that fails to hold the spent case (so it stays in the chamber while the next round feeds), short stroking that prevents full ejection, and faulty magazines with damaged

Question 19

Why Won't My AR-15 Bolt Lock Back on an Empty Magazine?

Accepted Answer

The bolt not locking back on an empty magazine is most commonly caused by undergassing (the bolt carrier does not travel far enough rearward to engage the bolt catch), a faulty magazine follower that does not activate the bolt catch, or an incorrectly installed or damaged bolt catch assembly in the

Question 20

Why Is My AR-15 Build Not Accurate? Common Accuracy Problems After Assembly

Accepted Answer

The most common accuracy problems on new AR-15 builds are an improperly torqued barrel nut (causing barrel movement), a non-free-floated handguard putting pressure on the barrel, loose scope or optic mounting, a crown damaged during assembly, and using the wrong ammunition for your twist rate. Most

Question 21

What Is the Best 5.56 Ammo for Home Defense vs Range Use?

Accepted Answer

For home defense, use a quality 55- to 62-grain soft point or barrier-blind hollow point like Hornady 75gr TAP, Speer Gold Dot 64gr, or Federal Fusion 62gr. These fragment or expand quickly, reducing over-penetration risk. For range practice, use brass-cased 55-grain FMJ like Federal American Eagle,

Question 22

What Is the Difference Between Hollow Point and FMJ Ammo?

Accepted Answer

Full metal jacket (FMJ) ammunition has a solid copper jacket that covers the lead core, causing it to retain its shape on impact and penetrate deeply. Hollow point (HP) ammunition has an open cavity in the nose that causes the bullet to expand on impact, creating a larger wound channel while reducin

Question 23

Does Steel Case Ammo Damage Your Gun?

Accepted Answer

Steel-cased ammunition does not damage your gun in any meaningful way, but it does cause slightly more wear on the extractor and chamber over tens of thousands of rounds compared to brass. The real trade-off is cost savings versus slightly increased wear. For most shooters, the money saved buying st

Question 24

What Is the Best 9mm Ammo for Self-Defense?

Accepted Answer

The top 9mm self-defense loads are Federal HST 147gr, Speer Gold Dot 124gr +P, and Hornady Critical Duty 135gr +P. All three meet FBI penetration standards (12 to 18 inches in calibrated gelatin), expand reliably through heavy clothing, and have proven track records with law enforcement agencies.

Question 25

6.5 Creedmoor vs .308 Winchester, Which Is Better?

Accepted Answer

The 6.5 Creedmoor has less recoil, shoots flatter, drifts less in wind, and retains more energy at distance than the .308 Winchester. The .308 has wider ammunition availability, lower cost per round, more bullet weight options, and a longer track record. For precision shooting and hunting beyond 400

Question 26

What Is the Difference Between Supersonic and Subsonic 300 Blackout?

Accepted Answer

Supersonic 300 Blackout (110 to 125 grains, 2,200 to 2,350 fps) delivers rifle-level terminal performance similar to 7.62x39 AK ammunition and is effective for home defense and hunting to 300 yards. Subsonic 300 Blackout (190 to 220 grains, 1,000 to 1,050 fps) is designed specifically for suppressed

Question 27

How Do You Read an Ammunition Box Label? What Do the Numbers Mean?

Accepted Answer

An ammo box label tells you the caliber (cartridge name), bullet weight in grains, bullet type (FMJ, HP, SP, etc.), muzzle velocity in feet per second, muzzle energy in foot-pounds, and round count. For example, 'Federal American Eagle 5.56x45mm 55gr FMJ' means Federal brand, American Eagle line, 5.

Question 28

What Is the Best Bulk Ammo for Range Practice?

Accepted Answer

The best bulk range ammo balances reliability, cleanliness, and cost. For 5.56/.223: Federal American Eagle XM193 or PMC Bronze 55gr FMJ. For 9mm: Federal American Eagle 115gr or Blazer Brass 115gr FMJ. For .308: Federal American Eagle 150gr FMJ or PMC Bronze 147gr. Buy in 500- to 1,000-round cases

Question 29

Is +P and +P+ Ammo Safe for My Gun?

Accepted Answer

+P ammunition is loaded to higher than standard pressure (typically 10 percent over SAAMI standard) and is safe for modern firearms rated for it, most guns manufactured after 1990 handle +P without issues. +P+ exceeds SAAMI specifications entirely and should only be used in firearms explicitly appro

Question 30

9mm vs .45 ACP vs .40 S&W, Which Caliber Should I Choose?

Accepted Answer

For most shooters, 9mm is the best all-around choice. It offers the highest capacity, lowest recoil, cheapest practice ammo, and with modern hollow point ammunition, terminal performance nearly identical to .45 ACP and .40 S&W. The .45 ACP makes the biggest hole and has a loyal following but holds f

Question 31

What Is the Best Hunting Caliber for Different Game Sizes?

Accepted Answer

For varmints and predators (coyotes, prairie dogs): .223 Remington or .22-250. For medium game (whitetail deer, antelope): .308 Winchester, 6.5 Creedmoor, or .30-06. For large game (elk, moose, bear): .300 Winchester Magnum, .338 Lapua, or .30-06 with heavy bullets. Match caliber to game, using too

Question 32

What Is the Best First Pistol for Beginners?

Accepted Answer

The best first pistol for most beginners is a full-size or compact 9mm striker-fired handgun. The top recommendations are the Glock 19 (compact, 15 rounds, most aftermarket support in existence), Smith & Wesson M&P 2.0 Compact (best factory trigger, aggressive grip texture), and Sig Sauer P320 Compa

Question 33

Glock 19 vs Sig P365 vs S&W M&P, Which Should I Buy?

Accepted Answer

The Glock 19 is the best all-around choice with unmatched reliability and aftermarket support. The Sig P365 is the best option if concealability is your top priority, it holds 10 to 15 rounds in a micro-compact package. The S&W M&P 2.0 Compact has the best factory trigger and ergonomics of the three

Question 34

What Is the Difference Between Striker-Fired and Hammer-Fired Pistols?

Accepted Answer

Striker-fired pistols (Glock, M&P, P320) use an internal spring-loaded striker to fire the cartridge, resulting in a consistent trigger pull every time. Hammer-fired pistols (CZ 75, Beretta 92, Sig P226, 1911) use an external or internal hammer, offering either double-action/single-action (DA/SA) wi

Question 35

What Is the Best Concealed Carry Gun for My Body Type?

Accepted Answer

For larger-framed individuals, a compact pistol like the Glock 19 or M&P 2.0 Compact conceals easily at 3 to 5 o'clock or appendix position. For average builds, a Sig P365XL or Glock 48 offers the best balance of shootability and concealability. For smaller-framed individuals, a micro-compact like t

Question 36

What Is the Best Handgun for Home Defense?

Accepted Answer

The best home defense handgun is a full-size or compact 9mm with a weapon-mounted light, night sights, and loaded with quality hollow point ammunition. Top choices are the Glock 17 or 19 with a Streamlight TLR-7A, Sig Sauer P320 with a TLR-1 HL, or Smith & Wesson M&P 2.0 full-size with a Surefire X3

Question 37

How Do I Choose a Holster? IWB vs OWB vs Appendix Carry Explained

Accepted Answer

For concealed carry, an inside-the-waistband (IWB) Kydex holster at the appendix (AIWB) or 3 to 4 o'clock position is the most common and effective choice. For open carry, range use, or duty use, an outside-the-waistband (OWB) holster provides comfort and faster draws. Appendix carry (AIWB) offers t

Question 38

What Should I Look for When Buying a 1911?

Accepted Answer

For a reliable 1911, prioritize a forged steel frame (not cast), a quality barrel with tight lockup, properly fitted extractor, and a reputation for reliability from the manufacturer. Top picks by budget: Springfield Armory Garrison ($750 to $850), Dan Wesson Specialist ($1,600 to $1,800), and Wilso

Question 39

Revolver vs Semi-Auto, Which Is Better for a First-Time Gun Owner?

Accepted Answer

For most first-time gun owners, a semi-automatic pistol in 9mm is the better choice. It offers higher capacity (15+ rounds vs 5 to 6), faster reloads, more affordable practice ammunition, and less felt recoil. Revolvers have advantages for specific uses, they are simpler to operate, never jam from l

Question 40

Do I Need to Break In a New Pistol? How Many Rounds?

Accepted Answer

Most modern polymer striker-fired pistols (Glock, M&P, Sig) do not require a formal break-in, they should run reliably from round one. However, running 200 to 500 rounds through any new firearm before relying on it for self-defense is strongly recommended to verify function, identify any defects, an

Question 41

What Are the Most Common Handgun Malfunctions and How Do I Fix Them?

Accepted Answer

The three most common handgun malfunctions are: failure to feed (slide does not fully chamber a round, tap the magazine base, rack the slide, reassess), failure to eject/stovepipe (spent case caught in the ejection port, lock the slide back, strip the magazine, rack three times, reinsert, rack, fire

Question 42

What Are the Best Pistol Upgrades in Order of Priority?

Accepted Answer

The best pistol upgrades in order of priority are: 1) Night sights or a red dot optic ($100 to $400), 2) Weapon-mounted light ($100 to $300), 3) Quality holster ($50 to $120), 4) Better trigger ($50 to $250), and 5) Extended magazine release or slide stop ($20 to $50). However, the most impactful up

Question 43

What Is the Difference Between a Red Dot and a Holographic Sight?

Accepted Answer

A red dot sight uses an LED reflected off a coated lens to project a dot onto the glass. A holographic sight uses a laser-recorded holographic reticle pattern. Red dots are lighter, cheaper, have longer battery life (50,000+ hours vs 500 to 1,000 hours), and work at all magnification levels. Hologra

Question 44

What Is the Best AR-15 Optic for My Budget?

Accepted Answer

Under $200: Sig Romeo 5 red dot ($120) or Holosun HS403B ($140). Under $400: Holosun 510C ($280) or Vortex Strike Eagle 1-6x ($300). Under $700: EOTech XPS2 ($500) or Vortex Razor HD-E 1-6x ($600). Under $1,000: Aimpoint T-2 ($900) or Vortex Razor Gen III 1-10x ($900). Over $1,000: Aimpoint ACRO P-2

Question 45

How Do I Zero a Red Dot Sight on My AR-15?

Accepted Answer

Zero your red dot at 50 yards for a 50/200 zero, or at 36 yards for a true 100-yard zero. A 50/200 zero means your bullet crosses the line of sight at 50 yards going up and again at approximately 200 yards coming down, staying within plus or minus 2 inches from 0 to 250 yards with M193 55gr ammuniti

Question 46

LPVO vs Red Dot, Which Is Better for My AR-15?

Accepted Answer

A red dot is better for home defense, CQB, and engagements inside 200 yards, it is faster, lighter, and always at 1x with unlimited eye relief. An LPVO (Low Power Variable Optic, typically 1-6x or 1-8x) is better if you need to identify and engage targets from 50 to 600 yards, it gives you magnifica

Question 47

MOA vs MRAD, Which Reticle System Should I Choose?

Accepted Answer

Neither is objectively better, both measure angles for adjusting bullet impact. MOA (Minutes of Angle) works in inches and is more intuitive for shooters who think in imperial units: 1 MOA equals approximately 1 inch at 100 yards. MRAD (Milliradians) works in a base-10 system: 1 MIL equals 3.6 inche

Question 48

What Is the Best Optic for a Home Defense Rifle?

Accepted Answer

The best optic for a home defense rifle is a red dot with shake-awake capability and long battery life, paired with a weapon-mounted light. Top choices: Aimpoint PRO ($450) for bombproof reliability, Holosun 510C ($280) for best features per dollar, or Sig Romeo 5 ($120) for a budget-friendly option

Question 49

Is a Magnifier Behind a Red Dot Worth It?

Accepted Answer

A flip-to-side magnifier behind a red dot gives you the best 1x performance of any setup with on-demand 3x or 6x magnification for target identification and precision shots at 200 to 400 yards. It is worth it if you primarily work at close range but occasionally need to reach out farther. It is not

Question 50

How Do I Choose the Right Scope Rings and Mounts for My Rifle?

Accepted Answer

Match your scope tube diameter (30mm or 34mm), your rifle's mounting system (Picatinny rail, Weaver, or proprietary), and the correct ring height so the scope clears the barrel and any front sight with minimal gap. For AR-15 platforms, use a one-piece cantilever mount. For bolt-action rifles, use ma

Go from confused to confident builder.

Start Here

AR-15 Advanced (116)

Gas Systems (7)

Compatibility (7)

Troubleshooting (7)

Ammo & Caliber (102)

Pistol & Handgun (55)

Optics (35)

Shotgun (18)

Long Range (20)

Maintenance & Safety (36)

Legal & NFA (639)

Can't Find Your Answer?