Barrel Length and Velocity in a .223 Rem — Barrel Cut-Down Test
We often receive questions from varmint hunters and AR shooters regarding barrel length. They want to know how much velocity they will loose if they run a shorter barrel in their .223-Rem rifle. Our friends at Rifleshooter.com did a test that provides some surprising answers to that question.
With barrels, one always wonders “Can a little more length provide a meaningful velocity gain?” To help answer that question, Rifleshooter.com performed an interesting test, cutting the barrel of a .223 Rem rifle from 26″ all the way down to 16.5″. The cuts were made in one-inch intervals with a rotary saw. At each cut length, velocity was measured with a Magnetospeed chronograph. To make the test even more interesting, four different types of .223 Rem/5.56 ammo were chron’d at each barrel length.
Test Barrel Lost 25.34 FPS Per Inch (.223 Rem Chambering)
How much velocity do you think was lost, on average, for each 1″ reduction in barrel length? The answer may surprise you. The average speed loss of the four types of .223/5.56 ammo, with a 9.5″ shortening of barrel length, was 240.75 fps total (from start to finish). That works out to an average loss of 25.34 fps per inch. (See inch-by-inch data HERE.)
| 5.56/.223 Barrel Cut-Down Speed Test 26″ to 16.5″ | Start FPS at 26″ | End FPS at 16.5″ | Total Loss | Average Loss Per Inch |
| UMC .223 55gr | 3182* | 2968 | 214 | 22.5 FPS |
| Federal M193 55gr | 3431 | 3187 | 244 | 25.7 FPS |
| Win m855 62gr | 3280 | 2992 | 288 | 30.3 FPS |
| Blk Hills .223 68gr | 2849 | 2632 | 217 | 22.8 FPS |
*There may have been an error. The 25″ velocity was higher at 3221 fps.
Rifleshooter.com observed: “Cutting the barrel from 26″ to 16.5″ resulted in a velocity reduction of 214 ft/sec with the UMC 223 55-grain cartridge, 244 ft/sec with the Federal M-193 cartridge, 288 ft/sec with the Winchester M855 cartridge and 217 ft/sec with the Back Hills 223 68-grain match cartridge.”
How the Test Was Done
The testers described their procedure as follows: “Ballistic data was gathered using a Magnetospeed barrel-mounted ballistic chronograph. At each barrel length, the rifle was fired from a front rest with rear bags, with five rounds of each type of ammunition. Average velocity and standard deviation were logged for each round. Once data was gathered for each cartridge at a given barrel length, the rifle was cleared and the bolt was removed. The barrel was cut off using a cold saw. The test protocol was repeated for the next length. Temperature was 45.7° F.”CLICK HERE to Read the Rifleshooter.com Test. This includes detailed charts with inch-by-inch velocity numbers.
Much Different Results with 6mmBR and a Longer Barrel
The results from Rifleshooter.com’s .223/5.56 test are quite different than the results we recorded some years ago with a barrel chambered for the 6mmBR cartridge. When we cut our 6mmBR barrel down from 33″ to 28″ we only lost about 8 FPS per inch. Obviously this is a different cartridge type, but also our 6mmBR barrel end length was longer than Rifleshooter.com’s .223 Rem start length. Velocity loss may be more extreme with shorter barrel lengths.
Similar Posts:
- Surprising Results in .223 Rem Barrel Cut-Down Velocity Test
- .223 Rem Velocity by Barrel Length — Cut-Down Test Results
- Velocity Per Inch in .223 Rem — Barrel Cut-Down Test Results
- .223 Rem Barrel Cut-Down Test — Velocity Loss by the Inch
- .223 Rem Velocity Per Inch Revealed by Barrel Cut-Down Test
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Tags: .223 Rem, 5.56, 5.56x45, Barrel Test, Cut-Down, Rifleshooter.com
This year as well as last Lear I went Sage RT hunting in Oregon with three of my buddies.
I shoot my AR-15 with a 24″ Stainless bull barrel and Privi-Partisan 68 grain Match ammo. My friends shoot 22s and HMR17s at 10 to 250 Yds.
I shoot 250-500 Yds. I was amaxed that I only had to raise 1-1/2 Mil dots to vaporize hundreds of these Chipmonk to Grey sqyirisize Varmints at 500 Yards. What a fun time helping the farmers get rid of these destructive pests by the hundreds in a day.
M-193 Ball (55gn FMJ) appears to have been optimised for the 20″ barrel of the AR-15 / M-16.
Back when Australia still had a sense of humour, I had several AR-15 rigs. One had a 24″ barrel with 1:8″ twist rifling. Very nice with 68gn HPBTs.
With Ball or equivalent loads, there was little improvement in MV over the standard 20″ job, leading me to suspect the “optimisation” of that ammo for rifles with a 20″ tube.
My “pet” bullet was the Hornady 60gn HP, which was (and still is) a superb performer.
Slightly compressed loads (25.5gn)of ADI/Mulwex AR2206, (similar to 3031, almost the same as BLC2 or 4895) would consistently print under 3/4″ at 100 from a stock-standard SP-1. (2-7x Leupold clamped on top; I’m not THAT good with iron sights). The Hornady bullet is short enough to:
1. Stabilize in a 1:12″ twist barrel at “warm” but realistic velocities from the Colt original chromed rifling.
2. Not take up a lot of “powder space” when seated to feed from a magazine, thus enabling use of said powder space.
Even more interesting was that lighter charges of the same powder produced noticeable pressure signs, like primer “cratering”, whereas the 25.5 left a very slightly “flattened” primer, (Federal), but NO cratering around the striker impact.
Shooting squirrels at 500 yards with a semi auto 223 is pretty amazing. I shoot 1″ groups at 300 with a 243 85gr or 100gr, out of a sporter barreled bolt action, and I thought that was good. But that’s nowhere near hitting squirrels all day at 500. I didn’t think a 55gr leaving at 2900 could be that stable and predictable.
…If I were that accurate with my 243, I could shoot elk in the head at 700 yards. Don’t think I’d ever take that shot though.