Banana Ballistics AR-10 Vs Bolt Action Velocity - MDT Mention

The question seems simple: does an AR-style rifle lose velocity compared to a bolt-action? While the question appears simple, the answer requires testing and validation. That’s what Banana Ballistics seeks to do in a video titled AR-10 vs Bolt Action: BIG Difference in Velocity?

The hypothesis is that a closed action, such as a bolt rifle, will report faster velocities compared to an AR-style rifle that uses direct gas impingement to cycle a bolt. The theory is that the dwell time of gas going down the gas tube will create a pressure drop, thus producing slower velocities. Makes sense, kind of. (unfortunately, there is a flaw that I’ll mention at the end).

The testing format is straightforward. A bolt action rifle, chambered in 308, with a 16” 1/10 twist 6-groove barrel, went up against a large frame AR with the same barrel parameters. The only difference is that the AR used an adjustable gas block, but the valve was fully opened for testing. (One note: gas port size varies on AR barrels, with many major manufacturers increasing the size to ensure proper cycling). All ammo was consistent within the same box or the same lot of reloads. Bullet weights consisted of 147gr FMJ, 165gr Soft Points, and 208gr ELDM. A MagnetoSpeed Chronograph was used for velocity testing. (In the video, the chronograph was not consistently capturing the velocities of the AR. Unfortunately, the handguard was too big, creating too much gap between the chronograph and the barrel. After the first round of testing, the handguard was taken off, and the chronograph was mounted directly to the barrel).

Initial testing proved negligible, with the bolt action and gas gun reversing order on various loads to see which was faster. After discouraging results, the gas port screw was tightened on the AR to close off any gas completely. This turns the gun into a straight-pull rifle rather than a semi-automatic one, but it was done to gather as much information as possible. The results were more of the same.

In summary, the testing performed by Banana Ballistics did not prove that one system produced better velocities over the other. The test led to more questions. That’s where a major error occurred. The test used 16” barrels. At face value, that might not mean much. But it could make all the difference. Of course, the longer the barrel, the more time the powder burns, which builds pressure and generates faster speeds. Of course, the law of diminishing returns means this isn’t exponential, and at a certain point, the reverse will happen as friction builds and pressure drops. But on a gas gun with a 16” barrel, the gas block is not far from the muzzle. That leaves very little time between the bullet exiting and gas escaping down the gas tube. If the barrel were longer and the distance between the muzzle and gas port greater, would that make a difference? The biggest thing to remember is that everything is happening in milliseconds. Even if the hypothesis is proven, are the results significant enough to factor in? This is all hypothetical but an interesting question that could further validate or disprove Banana Ballistics’ original hypothesis.

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