Increased barrel length increases muzzle velocity for most larger centerfire cartridges. This is why you’ll see F-Open guns with barrels up to 32″ in length. There is a limit. At some point, increased length of the barrel may not result in any additional velocity. In the case of rimfires, too much barrel can reduce MV. Today’s showcase examines how barrel size affects muzzle speed, both for centerfire and rimfire. Above you can see what is possibly the longest barrel ever fitted to a standard rifle. The team at MDT (Modular Driven Technologies), created this to test how velocity changes with barrel length. The MDT video, the first of our Saturday video showcase, shows the results of the testing with this unique rifle. The MDT rimfire test is then followed by additional tests using the.308 Winchester cartridge, 6.5 Creedmoor cartridge, and.223 Rem. The World’s Longest Barrel to Determine Velocity Change. This is the most interesting barrel length velocity test ever shown on video. The MDT team (Modular Driven Technologies), started with a 69″-long barrel chambered for the.308 Winchester. Federal Gold Medal Match with 175gr Sierra HPBT bullets (Video 3:30) was used. This barrel was actually made from multiple sections. That was a challenge. Velocity was measured by one-inch increments, starting at 69″ and going down to 19.5″ The speed was 2778 FPS at 69′, and 2567 FPS at the 19” barrel. The tester at MDT noted that the difference was 211 FPS between the longest and shortest points. Note that the velocity showed a fairly constant change in inches from 19” up to 45′”. Going beyond 36” can actually increase the velocity. From 45” to 60” inches, the velocity actually decreased. See the video at 6:55 and look at the chart below. This video is Part 2 of MDT’s test “Cutting the World’s Longest Rifle”. This time, the team fires the.22 LR cartridge out of an ultra-long tube. The results might surprise you. “Get ready to be surprised as the MDT team chops a.22 LR rimfire rimfire barrel inch by inch and records velocities for each barrel length. The MDT team conducted this test to determine the optimal barrel length for a.22 LR from the perspective of velocity. How long is too much? How short is too brief? Does shorter always mean faster? Does longer always mean slow? In fact, MDT testers determined that with standard rimfire ammo, the velocity began to decline after 16″ length. This surprised some testers. With the small.22 LR, increased friction in the barrel can reduce muzzle velocity. 6.5 Creedmoor Barrel length test (24″ to 16″) Western Powders testers cut down a test barrel chambered in 6.5 Creedmoor one inch at a a time for this video. Chronographs were used to measure the velocity of five rounds at each length. The velocity loss was calculated per inch of barrel decrease. Overall, the velocity loss recorded from 24″ to 16″ was 197 FPS. This is almost exactly 25 FPS for each inch of barrel length. As you can see in the graph at the 4:00 minute mark, the velocity loss rate was relatively constant inch by inch. .223 Rem Velocity Testing (9 Guns 7.5”-20” Barrels). In this video the team at Classic Firearms tests different firearms chambered in.223 Rem. This video starts with a Springfield Saint Victor AR-type gun with a very small 7.5” barrel. This resulted in a 2183 FPS on average. The team then tested eight additional guns with barrel lengths that increased with each successive gun. The test ended with a Colt XM16E1 rig that had a 20” barrel. This Colt AR averaged 3152 FPS. Below is a list of the guns (and their barrel lengths). The overall results will be discussed at the time-mark of 13:45. Video Time — Test Lengths — 7.5″ to 20″ 2:11 — 7.5″ Springfield St.V. AR Pistol 2183 FPS
3:23 — 10.3″ DD MK18, 2513 FPS
4:34 — 11.8″ PWS MK111 Ar Pistol with 2644 FPS
5:35 — IWI Zion AR Pistol 12.5”, 2789 FPS. 7:50 — M4A1 Pin&Weld, 14.5”, 2793 FPS.
9:30 — 16” SIG Sauer MCX Virtus Rifle, 2865 FPS
10:18 — 16″ LWRC IC Di Rifle, 2872 fps
11:17 — 18″ DD MK12 rifle, 2998 FPS
12:28 — 20″ Colt XM16E1 rifle, 3052 FPS.308 Winchester – 16” barrel vs. 24-” barrel velocity With the.308 Win, many hunters prefer a short barrel for lighter carrying weight. In this video Gavin Gear from UltimateReloader.com compares the.308 Win velocity with a 16″ barrel and a 24-inch barrel, using the same ammunition. Gavin says: “We asked you for input on our build. You all wanted a 16” barrel, so “Shorty” was born! Looking to compare velocities, I brought out my match .308 Win with a 24” barrel to compare the results with some Hodgdon data.” CLICK HERE to read full report on UltimateReloader.com. RifleShooter.com Barrell Cut-Down Tests Along with these videos our friends at RifleShooter.com conducted a series of barrel cut-down testing, starting with barrels that were fairly long. The velocity was measured for each inch reduction. Most of us have a.223 Rem. rifle. Thanks to our friends at Rifleshooter.com, we can now assess how velocity changes as barrel length for this popular round. Rifleshooter.com conducted an interesting test by cutting the barrel of the.223 Rem from 26″ to 16.5″. The cuts were made at one-inch intervals using a rotary tool. Magnetospeed chronographs were used to measure the velocity at each cut length. To make the test more interesting, four types of.223 Rem/5.56 ammunition were chronographed at each barrel. Rifleshooter.com, the team that conducts these test, has a full service gun shop called 782 Custom Gunworks. Visit 782guns.com. READ RifleShooter.com’s 5.56/.223 Barrel Test Article >> Test Barrel Loses 25.34 FPS per Inch (.223 REM Chambering)
What do you think the average velocity loss is for every 1″ reduction in barrel length? You may be surprised by the answer. The average speed loss for the four types.223/5.56 ammunition, with a barrel length reduction of 9.5”, was 240.75fps (from start-to-finish). This is equivalent to a loss of 25.34 feet per inch. 5.56/.223 Barrel Cut Down Speed Test 26″ to 16.5″ Start FPS 26″ End FPS 16.5″. Total Loss Average Loss per Inch UMC.223 55gr. 3182* 2968 217 22.8 FPS Federal M19355gr.3431 3187 244 25.7 FPS Win.m85562gr.3280 2992 282 30.3 FPS Blk. Hills.223 68gr.2849 2632 The 25” velocity is higher at 3221 fps. See inch-by -inch Barrel Cutdown Velocity Data HERE. Rifleshooter.com noted: “Cutting the 26″ barrel down to 16.5” resulted in a reduction of 214 ft/sec for the UMC 223 cartridge with a 55-grain bullet, 244 ft/sec for the Federal M-193 with 68-grain bullet, 288 ft/sec for the Winchester M855 with 68-grain bullet, and a.
The testers described the procedure as follows: “Ballistic information was collected using a Magnetospeed ballistic chronograph mounted on a barrel.” The rifle was fired at each barrel length from a front bag with rear rests, using five rounds of each type. Each round was logged with the average velocity and standard deviation. Once the data for each cartridge was collected at a certain barrel length, the rifle’s bolt was removed. The barrel was removed using a cold-saw. The test protocol was repeated with the next length. The temperature was 45.7degF. Click HERE to read the Rifleshooter.com test. This includes detailed charts that show velocity in inches by inches. Rifleshooter.com has more barrel cut-down tests.
Rifleshooter.com performed barrel cut-down testing for many other calibers/chamberings, including 6mm Creedmoor and.308 Winchester. Rifleshooter.com has these results.
