Surprising Results in .223 Rem Barrel Cut-Down Velocity Test
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:
- Velocity Per Inch in .223 Rem — Barrel Cut-Down Test Results
- Barrel Length and Velocity in a .223 Rem — Barrel Cut-Down Test
- .223 Rem Velocity by Barrel Length — 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
Ya thats been my experience in .223. Around 20-30 fps max velocity change per inch. Not surprising. The average change ive seen over many barrels chambered .223 according to my records has been 18 fps.
I see the 6br was cut from 33″ to 28″. I believe if it was cut from 26 to 16″ there would have been a much greater change in velocity per inch. Beyond 28″ the change becomes slight.
Wouldn’t the velocity gains change with respect to the burn rate of the powder used. A slower burn rate showing more velocity with a longer barrel.
I am not the least bit surprised by these results. Walt Berger said years ago that velocity loss was about 25.3fps. No surprise at all.
Then there is the 6BR test. Well if you use a really fast burning powder its going to mess up your results like it did with the 6BR test.
Editor: I don’t think the 6BR test was “messed up” in the least. Many 6BR and Dasher shooters have been looking for 20-50 fps more velocity, and they wondered if it made sense to “go long” (to 32-33″), as some Palma shooters did. Most current 600-yard benchrest shooters are running barrels in the 27-30″ range. We used H4895, which is a bit faster than Varget, but still a popular powder for the 6BR cartridge. H4895 is quite a bit slower than N133 or LT32.
Were the losses greater as the barrel got shorter?
It’s a good thing QuickLOAD tells me this exact same information, without costing me a dime on cut barrels.
Just goto the Hodgdon reloading site and choose “pistol,” for .223 or .308 and it will Give you velocities for pistol (15 inch) barrel and Rifle (24 inch) barrel
If you look at the PDF data from the old accurate site Accurate 5744 is some MAGICAL POWDER! It burns like a Mangum pistol powder and it’s only good for 3 bullet weights in .308 a 110gr, 168gr, & 208gr. The 168gr load is 10gr less than Accurate 2520 and only 4 fps slower! Is AMAZING in short barrel .308’s!