Why it matters: Q is arguing in public that a 6mm Creedmoor rifle can replace 6mm ARC on weight and energy, using a prototype's first chronograph numbers. The same session produced a barrel-length result that, if it holds, would change how buyers choose a short 6.5 Creedmoor.
Q LLC posted a video to YouTube on November 6 under the title “Q | DEVELOPING THE BOOMBOX | 6MM CREEDMOOR FIRST SHOTS.” It runs about 19 minutes and belongs to the company's documentary series on its Boombox rifle. The description says Mitch and KB take the platform to the range in the new chambering. On camera, one speaker calls the rifle a prototype and the first Boombox in 6mm Creedmoor.
This is the manufacturer's own video, and every velocity below is a chronograph reading spoken by Q's staff. The rifle has a 13-inch barrel, and one speaker says that in this configuration it weighs “way under 6 lb.” The speakers give no measured figure. The stated goal for the day is modest: collect muzzle velocity data and “pop a box” through each gun.
Why Q argues for 6mm Creedmoor over 6mm ARC
The opening speaker starts with what 6mm ARC does well: it shoots far, recoils lightly and fits an AR-15. The objections follow. The cartridge needs a different bolt, the speaker says, and opening up an AR-15 bolt face weakens it, which pushes makers toward costlier materials. The speaker also cites limited magazine capacity and the lack of standard AR magazines, and says such rifles are fine for commercial and casual users but not as reliable as they could be for Q's military focus. The speaker offers no failure data on those points.
The alternative, in the speaker's telling, is a barrel swap. Q's marketing has described the Boombox moving from 8.6 Blackout to 6mm or 6.5 Creedmoor that way, and a Silencer Shop dealer listing says the rifle takes standard .308 and 6.5 Creedmoor magazines. The speaker says “tier one guys” tell Q they like 6mm ARC in another company's 14.5-inch rifle, and that a quick calculation on muzzle velocity and weight points to a Boombox roughly 20% lighter with 20% more energy on target. “We're going to actually check it,” the speaker adds.
Boombox 6mm Creedmoor muzzle velocity from a 13-inch barrel
The first load is described as “like 103 or 108 grain.” The shooters read an average of 2,581 feet per second and later mention 2,620. One says that is 100 fps faster than Q's 16-inch 6.5 Creedmoor rifles, and a speaker adds that it will carry less energy than those rifles. One speaker then says that even a 24-inch 6mm ARC does not reach that velocity.
Published figures read differently on that last point. Hornady's 103-grain ELD-X in 6mm ARC is advertised at 2,800 fps from a 24-inch test barrel, and American Rifleman's 2020 review recorded a 2,671 fps average for that load from a 16-inch CMMG carbine. Those numbers come from different rifles, ammunition lots and conditions. Q's speakers do not report firing a 6mm ARC rifle in this session.
The second load is a 90-grain CX, a solid copper Superformance round. A speaker reads 3,325 fps off its box against about 3,050 for the first load and expects a gain of about 10%. The readings called out mostly fall between 2,840 and 2,879 fps, with one near 2,920, and the team gives a 2,867 average. “Arc just became irrelevant,” one speaker says.
One problem surfaces during the session. A shooter reports a bullet tip breaking off and describes a case with a smashed shoulder, which the speaker says matches the shape of the tip. The speaker says plastic tips are “just not good for gas guns,” points to the non-tipped Barnes TSX, and suggests an aluminum tip as a sturdier option.
6.5 Creedmoor Boombox: 13-inch vs 14.5-inch barrel velocity
“An inch and a half of barrel moved velocity 5 to 11 fps in the strings Q read out, against roughly 150 fps for the inch and a half above it.”
Avery Lindqvist, The ReticleThe team then shoots a 6.5 Creedmoor Boombox with a 143-grain ELD-X, using the same scope and silencer so the weights match. The speaker describes this as a felt-recoil check rather than a measurement: more recoil than the 6mm, with a bullet “40% bigger,” but “half of what a 308 feels like” in a heavy .308 gas gun. A second shooter says the 6mm is softer but that the difference would not decide which rifle to pick, while allowing that lighter recoil could help a shooter stay in a night vision or thermal eye box.
That rifle averages about 2,350 fps, which the team puts at 140 to 150 fps behind its 16-inch guns. The speakers first treat the gun as a 13-inch, then work out that it is a 14.5. Firing the 13-inch and 14.5-inch guns with the same ammunition in two strings gives differences of about 11 and 5 fps. One speaker calls that “very surprising.”
Summing up, a speaker says Q would not build a 14.5 at all, but a 16 and a 13, or maybe a 12. The extra inch and a half buys about 10 fps, which at 2,350 fps the speaker calls a rounding error. The 16-inch number is cited from Q's existing guns, and the 13-inch comparison rests on those two strings.
One speaker extends the comparison, saying a 14.5-inch 6.5 Creedmoor gets higher velocity than an 18-inch 6mm ARC with a bullet 40% heavier, and that there is “no reason to have the arc cartridges” except for a casual buyer. That claim can be set against American Rifleman's 16-inch average above.
Energy figures for the Boombox 6mm Creedmoor and 6mm ARC
Q gives no energy readings, so the following are The Reticle's calculations from the standard kinetic energy formula. The 90-grain average of 2,867 fps comes to about 1,640 foot-pounds. The first load's 2,581 fps comes to about 1,520 to 1,600, depending on which bullet weight it was. The 6.5 Creedmoor load at 2,350 fps comes to about 1,750. American Rifleman's 16-inch 6mm ARC average with the 103-grain load comes to about 1,630. The speakers give no velocity for the 14.5-inch 6mm ARC behind their 20% estimate.
Another chambering also comes up during the 6.5 Creedmoor shooting. “I can't wait to shoot this thing in 308,” one speaker says.
For context
- Q's Boombox is an AR-pattern, direct-impingement semi-automatic rifle introduced in 8.6 Blackout, a .338-caliber cartridge Q designed on a shortened, necked-up 6.5 Creedmoor case.
- 6mm Creedmoor is a necked-down 6.5 Creedmoor, the shared case behind Q's argument that the change needs only a barrel.
- 6mm ARC is a Hornady cartridge built to fit the AR-15's 2.260-inch maximum overall length; American Rifleman reported in 2020 that the Defense Department had adopted it.
- A rifle barrel under 16 inches makes a short-barreled rifle under the NFA; ATF's Oct. 9, 2026 open letter says it will not enforce NFA approval and registration requirements for suppressors and short-barreled rifles, and state laws still apply.
