Is the 20-inch AR-15 a relic of the past, or does the “musket” still reign supreme? In this video, we put a custom 20″ Mk12-inspired clone head-to-head with a modern 14.5″ duty SPR to find out if the classic barrel length is truly obsolete.
We don’t just talk specs—we put both platforms through real-world testing: real-world CQB maneuverability drills around a standard 36″ doorway, staging and shooting inside and out of vehicles, a baseline chronograph velocity test, close-range bill drills, and a long-range hit probability test stretching all the way out to 750 yards.
The ballistics numbers vs. real-world maneuverability might surprise you. Watch to the end to see the data breakdown and find out which rifle wins out as the ultimate do-it-all platform.
If you enjoy practical, data-driven firearm comparisons, make sure to LIKE, COMMENT, and SUBSCRIBE to the channel!
***
### RIFLE SPECS:
**The 20-Inch Build (12.4 lbs loaded):**
* Barrel: Del-Ton 20″ (1:9 Twist)
* Stock: Fixed A2
* Rail: Daniel Defense Omega Quad Rail
* Gas System: Adams Arms Short-Stroke Piston
* Optic: Vortex Viper HST 4-16x (SFP) in a Burris PEPR Mount
* Offset Optic: Vortex Spark Red Dot
**The 14.5-Inch Duty/SPR (11.4 lbs loaded):**
* Base: Sig M400
* Furniture: Vltor Stock & B5 Systems Pistol Grip
* Optic: Vortex Razor HD Gen III 1-10x LPVO in an American Defense Mount
* Offset Optic: Holosun 407C on an Arisaka Offset Mount
* Light/IR: Streamlight Protac 2.0 slaved with TLR VIR II & Villain Weapon Systems lens
* NVG Setup: PVS-14 compatible
***
### TIMESTAMPS:
00:00 – Introduction & 20-Inch Rifle Specs
00:01:32 – 14.5-Inch Duty Rifle Specs
00:02:46 – Weight Comparison & Balance
00:04:38 – CQB & Room Entry Maneuverability (36″ Doorway)
00:09:23 – Vehicle Operations & Dismounting
00:10:28 – Shooting From Inside a Vehicle & Clearances
00:11:41 – Chronograph Velocity Test (Winchester White Box 55gr)
00:12:29 – Long Range Hit Probability (369, 589, & 750 Yards)
00:13:40 – Close Range Speed Drills & Bill Drills
00:14:23 – 90-Degree Target Transitions
00:15:04 – Vehicle Dismount & Engagement Drills
00:16:36 – Final Data Breakdown & Verdict: Is the 20″ Obsolete?
#AR15 #Mk12 #SPR #Ballistics #LongRangeShooting #TacticalTraining #FirearmReview #LPVO
Note to readers: Please click the share buttons above or below. Forward this article to your email lists. Crosspost on your blog site, social media, internet forums. etc.
Huge thanks to everyone watching! 12.4 lbs vs 11.4 lbs really surprised me when you consider everything packed onto that 14.5" work gun.
For the guys who still run a "musket" or a Mk12 clone: What's your setup weigh, and would you carry it daily over a shorty? Drop your specs below! 👇
One thing I noticed because when I served we didn't have optics. A2 iron sights is pretty much it. I have an A4 clone now with a Vortex Strike Eagle 1-8. I noticed on the BDC, the drops aren't as indicated. For example shooting out to 500, if I held on the 500 tick, I was sailing them. It was more like between the 400 and dead hold. I love the smoother shooting and flatter trajectory of the 20, so I prefer that. But a note to all you out there – go train with it and know your DOPE. Because the marks in the BDC are not universal, even for your caliber.
Colt 20” A4 guy here. Have a WOA free float handguard on it, it’s heavy but accurate and awesome. Geisselle 2 stage trigger.
If I'm on my own, I clear with a pistol.
You should drop a Geissele SSA-E or SSA-EX in your MK12 clone. Those are nice triggers for that setup.
Firearms are never obsolete, nice setups though.
Great comparison video! Thanks for the breakdown
🤘🤘
Awesome video
What a nice set up you have on your gun and garage.
Good video TLM
Good video! You put in alot of time and preparation and it shows in your personality and professionalism that makes it so great.
Is the 20-Inch AR-15 Actually Obsolete? (750 Yard Test)
The 5.56/.223 was developed by Stoner for a 20 inch rifle. Effective accurate shooting at distance falls off with shorter barrels. Carbine and mid length gas systems and barrels of an M4 Carbine are better for closer ranges.
The U.S. military chose the 14.5-inch barrel for the M4 Carbine to strike the ideal balance between maneuverability (for urban combat and vehicle deployment) and ballistic performance (retaining enough velocity to ensure the 5.56mm NATO round remains lethal at medium ranges). Going much shorter than 14.5 inches causes a rapid drop-off in the muzzle velocity needed for the 5.56mm round to fragment properly. The 14.5-inch length keeps muzzle velocity high enough (around 2,900 ft/s) for the bullet to remain effective out to around 500 meters.
A 20-inch AR-15 barrel maximizes the ballistic potential of 5.56/.223 ammunition. It delivers higher muzzle velocity, flatter trajectories, and extended effective range. The longer barrel allows for a smoother, softer-recoil "rifle-length" gas system and reduces muzzle flash.
Reliability: The dwell time (the amount of time the bullet stays in the barrel after passing the gas port) is highly optimized in a 20-inch barrel, ensuring consistent, reliable cycling even with heavily used or older magazines.
Reduced Muzzle Flash and Blast: The extra length allows the powder to fully burn inside the barrel, resulting in a much quieter shot with significantly less flash than shorter barrels. Less maneuverable and more weight are the trade offs.
❤
For me the 20” is just too much gun. The performance boost from the extra barrel length doesnt seem worth it