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Suppressors and Velocity Part 1

We had a meeting a week or so ago, that, like all of our meetings, quickly became sidetracked. What tied us up was a discussion regarding suppressors and their relationship to velocity.  Here were the schools of thought:

The suppressor makes no difference.  People that believed this idea was correct…..3

The suppressor reduces velocity.  People that believed this idea was correct…..1 but he was very strongly convicted in his theory.

The suppressor adds velocity. People that believed this idea was correct……1, a wise and wonderful human being who was treated like a heretic.

And finally one boss who asked us all:  “Shouldn’t we know this?  We are a ballistics lab after all.”

Winner:  Boss.


Result:
We set up an accurate and easy to transport Pro-Chrony on our pistol range and dug out a Ruger 22/45 Mark 4 Lite.  For testing we found a festive box of CCI standard velocity .22 Long Rifle cartridges marked “Merry Christmas 2016.  This was to be a test using empirical science practiced at its highest levels.

Our specially calibrated 22 LR ammunition prior to rigorous testing.

Velocity Unsuppressed
948, 937, 915, 927, 917
Average Velocity: 929 fps
Extreme Spread: 33 fps
Standard Deviation: 14 fps

With the eight inch Form 1 suppressor attached, the little Ruger’s 4.4 inch barrel produced these numbers:

Velocity Suppressed
947, 937, 951, 951, 948
Average Velocity: 947 fps
Extreme Spread: 14 fps
Standard Deviation: 6 fps

The suppressor on average increased the bullet’s velocity by a little less than 2%, showing an average increase of about 18 fps.  The heretic thought the reason was pretty simple.  Even though a suppressor allows plenty of room for the bullet to pass through the baffles, it is still a pressurized environment that is able to impart more velocity to the projectile.  There are a lot of variables at play in firearms, and I’m not saying that is universally true, but at least we can look at our boss and tell him we know the answer for this pistol, using this suppressor with this ammunition.

The nay-sayers say we need more testing.  They are certainly right.  Toward that end, we are going to add threading to a couple of our pressure testing barrels in calibers that are commonly suppressed and test them with and without suppressors in place.  The pressure traces and velocities should be interesting.  We’ll let you know what we find.