The discussion focuses on finding the most suitable AR-15 pistol barrel length among 7.5, 10.5, 11.5, and 12.5 inches. The hosts emphasize that there is no universal best choice because mission dictates gear. Needs differ for someone in wide-open rural areas, typical suburbs, or an apartment, and barrel length affects velocity, terminal effect, and accuracy. To keep the comparison consistent, they use Ballistic Advantage uppers so that only barrel length and gas system vary. All uppers are chambered for 5.56/.223, and the plan is to test them on the range with a chronograph, using the same lower and ammunition. They also mention interest in possibly expanding the testing to longer AR-15 barrel lengths up to 20 inches for a broader performance comparison.
The first upper examined is the 7.5 inch Ballistic Advantage configuration. It is described as very compact and about as short as they are comfortable going with 5.56 or .223, even though shorter barrels exist. The 7.5 inch setup is lighter and more maneuverable, which can be useful in tight spaces. However, they stress the significant increase in blast and concussion compared to a 16 inch rifle, especially indoors. The example given is standing next to someone shooting a 16 inch rifle with a standard muzzle device at an indoor range and then imagining that concussive effect multiplied several times with a 7.5 inch barrel. The tradeoff is clear: improved handling and compactness versus much harsher blast and reduced velocity.
At the range, they use a Garmin chronograph to measure feet per second with 55 grain factory ammunition across the four Ballistic Advantage uppers. All testing is done on the same SBR lower, using an Aimpoint optic in a Scalarworks mount that is moved between uppers to keep conditions consistent. The 7.5 inch barrel averages about 2,466 fps. Moving to the 10.5 inch barrel, the average jumps to roughly 2,767 fps, with one noticeably low round attributed to ammunition variation. The 11.5 inch barrel averages about 2,830 fps, and the 12.5 inch barrel averages about 2,882 fps. They note that the biggest velocity increase occurs between 7.5 and 10.5 inches, while gains from 10.5 to 11.5 and 11.5 to 12.5 inches are more incremental.
They repeat the chronograph testing with 62 grain ammunition, described as common green tip used frequently in military contexts. With the 7.5 inch barrel, 62 grain averages about 2,336 fps, slower than the 55 grain due to the heavier projectile. On the 10.5 inch barrel, 55 grain averages about 2,767 fps while 62 grain averages around 2,584 fps. The 11.5 inch barrel shows a 55 grain average of about 2,830 fps and a 62 grain average of roughly 2,671 fps. For the 12.5 inch barrel, 55 grain averages about 2,882 fps and 62 grain about 2,746 fps. Across all lengths, the heavier 62 grain loads run slower but follow the same pattern of increasing velocity with longer barrels, confirming consistent behavior between the two bullet weights.
They break down the velocity differences to highlight where barrel length changes have the most impact. With 55 grain ammunition, going from 7.5 to 10.5 inches yields roughly a 300 fps increase, which they consider significant. From 10.5 to 11.5 inches, the gain is about 63 fps, and from 11.5 to 12.5 inches, about 52 fps. With 62 grain ammunition, the same pattern appears: a large jump between 7.5 and 10.5 inches, then smaller increases between 10.5, 11.5, and 12.5 inches, on the order of 75 to 87 fps. Overall, the total difference from 7.5 to 12.5 inches is around 400 fps, but most of that gain occurs in the first three inches of added barrel length. The testing is kept controlled by using factory 55 and 62 grain loads and identical Ballistic Advantage uppers.
Using the data, they return to the question of application. A 7.5 inch AR-15 pistol, especially with a suppressor, can work for close quarters where compactness matters and engagement distances are short. Velocities in the 2,300 to 2,400 fps range with 5.56 still provide usable terminal effect and the ability to defeat intermediate barriers at close range, though with more blast. For users needing more reach and better terminal performance at distance, the 10.5, 11.5, and 12.5 inch barrels offer higher velocities, with the 12.5 inch often cited as a preferred short length. They note that agencies like the FBI have used 11.5 inch Colt M4-type carbines with 62 or 64 grain loads and consider effective penetration standards around 200 yards. Ultimately, the choice depends on environment, expected range, and whether a suppressor will be used.
Loading...