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Posted: 1/12/2011 2:31:13 AM EDT
I know someone has covered this here, but I did a search and could not find the answer. With adding a suppressor to your fire arm, does it decrease muzzle velocity or increase it? 
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| I don't have access to the numbers on this machine, but I seem to recall a 20-30 fps increase in velocity across the chronograph with most of my guns when suppressed. Ammunition makes a difference, as some are affected more than others. In any case, the velocity increase is largely unimportant, especially compared to the POI changes with and without the suppressors. |
Some suppressors increase velocity. The better suppressors are specifically designed to try to minimize any velocity difference. Why? Because different velocity can be a contributing factor to POI shift. 
The term "free bore boost" is used to describe the increase in velocity cause by a suppressor. What happens is the bullet leaves the barrel so friction stops. However, gases are still expanding behind the projectile and help to continue propelling the bullet through the suppressor but without the friction of the rifling. Make sense? As mentioned there are a lot of variables. Barrel length, atmospheric conditions, ammunition, and (of course) suppressor, etc. all can play factors. Mark |
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One of the main reasons this question comes up is that years ago the majority of silencers were integral and had holes drilled in the barrel to add sound reduction (or so they thought) and to reduce velocity.
The suppressed Sten guns of WW2 were 9mm (supersonic) and they used ports to get the velocity reduced to avoid the ballistic crack. They did the same thing with 22LR using high velocity ammo in certain weapons. Jon Arthur Ceiner used porting in the 60's and 70's to add sound reduction to some of the centerfire rifle suppressors he made. They reduced the velocity. Most of the Marlin Camp Carbines that have silencers are ported. Many of the 44 Mag and 45 ACP bolt guns that are suppressed use porting to some degree. Velocities are somewhat reduced. Muzzle cans seldom increase or decrease velocities by enough to warrant any serious concern. Free bore Boost as Bookhound mentions is what causes the increase in velocity when measurable. |
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