Slugs louder than Pellets?

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cea1960

cea1960

Member
Mar 12, 2017
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Oriental, North Carolina, United States
I've been testing the .177 12.5g NSA slugs in my 17fpe HW100BP-K. They definitely make tighter groups in wind at 48 yards than the Polymags (most accurate in my gun)

What I have noticed, and so did my friend, is the slugs are much louder leaving the muzzle than pellets.

Polymags are shooting at 977 and I haven't chronied the slugs yet, but I would have thought if they are moving slower, they would be quieter.

Has it to do with the ballistics?
 
What muzzle energy is each one producing? That would provide a clue.

Usually it's the reverse. At a given state of tune (no changes to hammer spring tension, operating pressure, etc.), what generally happens is the heavier projectile takes longer to begin accelerating...somewhat acting like a plug in the barrel, reducing the total amount of air that gets metered out for the brief time the valve is knocked open. Then by the time the projectile exits the muzzle, the residual pressure is less. Residual pressure is what determines the report from the muzzle, thus it would be less loud.
 
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What muzzle energy is each one producing? That would provide a clue.

Usually it's the reverse. At a given state of tune (no changes to hammer spring tension, operating pressure, etc.), what generally happens is the heavier projectile takes longer to begin accelerating...somewhat acting like a plug in the barrel, reducing the total amount of air that gets metered out for the brief time the valve is knocked open. Then by the time the projectile exits the muzzle, the residual pressure is less. Residual pressure is what determines the report from the muzzle, thus it would be less loud.
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This is what I assumed. I'll chrony it to find the energy, but so far every pellet I've tried has produced between 16.4 and 19.1 fpe.
 
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What muzzle energy is each one producing? That would provide a clue.

Usually it's the reverse. At a given state of tune (no changes to hammer spring tension, operating pressure, etc.), what generally happens is the heavier projectile takes longer to begin accelerating...somewhat acting like a plug in the barrel, reducing the total amount of air that gets metered out for the brief time the valve is knocked open. Then by the time the projectile exits the muzzle, the residual pressure is less. Residual pressure is what determines the report from the muzzle, thus it would be less loud.
Click to expand...

My Texan is the reverse though my FX Wildcat follows your logic, could this be because of the inline valve system on the Texan or that the regulator on the FX. Anyway when I shoot lighter projectiles in my texan it is not as near as loud as when i put heavies in 
 
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Willie, I'm not sure but you may have identified it. The Texan uses a balanced valve. That allows it to operate at very high energy levels without needing a massive amount of hammer strike (which would make it hard to cock). This explanation will be an oversimplification but a balanced valve works more like an on/off valve, whereas a conventional valve is more like a water faucet where the flow and duration can be manipulated. Thus I expect the lift and dwell of the balanced valve are influenced differently, allowing it to deliver comparatively more air to the heavier slug.
 
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