Hornady Critical Duty 9mm Velocity Testing

In a recent range session, I used my LabRadar to measure the velocity difference between barrel lengths for the Hornady Critical Duty 9mm 135 grain FlexLock standard pressure round. For the testing I used my SIG P365, my SIG P320 Carry, and my P320 X5 Full size pistols.  

Since I use this Hornady Critical Duty 9mm round in my SIG P320 Carry and my P365 everyday carry pistols, I was curious about the velocity difference between barrel lengths. My expectation going into the testing was that the P365 would record the lowest velocities and the X5 would record the highest velocities since it had a longer barrel.

However, that was not the case. The P320 Carry with its 3.9-inch barrel recorded the highest velocities. I fired ten rounds of the same lot number through each of the three pistols. The table below shows the results of my testing with the velocities in feet per second or FPS. 

Pistol	Barrel	Average	High	Low	Extreme Spread	Std Deviation
SIG P365	3.1 Inches	959	975	943	33	14.8
P320 Compact Carry	3.9 Inches	1038	1048	1019	29	13
P320 X5	5.0 inches	983	1010	974	37	15.3

I referenced the Lucky Gunner Handgun Self-Defense Ammunition Ballistics Test and looked at their results for the standard pressure Critical Duty round. In their 9mm Luger testing, Lucky Gunner used a Smith & Wesson M&P9C, 3.5-inch barrel—a barrel exactly halfway between the barrel lengths I used. The Lucky Gunner average velocity for five shots from the 3.5-inch barrel was 1053 FPS.

Hornady’s description of the Critical Duty states in part that it is: “Designed to meet the needs of those who demand superior barrier penetration and prefer a full‑size handgun for their personal protection.” To me, full-sized would mean a five-inch barrel. However, Hornady’s ballistics data for the Critical Duty 9mm 135 grain standard pressure round showed a velocity of 1010 FPS from a four-inch barrel.

So why was the velocity lower in the five-inch X5 barrel when compared to the 3.9-inch P320 Carry? I have no idea. Perhaps the burn rate for the powder Hornady uses is optimized for a four-inch barrel. I can speculate that the extra 1.1 inches adds a bit of drag to the bullet because the powder had burned at the 3.9-4.0 inch mark. However, that is pure speculation.

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* Lucky Gunner Labs did some interesting ballistics gel testing.  I recommend their research: https://www.luckygunner.com/labs/self-defense-ammo-ballistic-tests/#9mm