Suppressors Getting a ( 70 fps Vel. Boost ) . Dirty CB shot .

[softcock]

Getting a ( 70 fps Vel. Boost ) . Dirty CB shot . <span style="font-weight: bold"><span style="font-size: 11pt">no subsonic ( High Vel. Rounds only</span> </span>)
but this Vel. Boost is just happening only on the 1st Round dirty-CB shot . & I changed powders on it a few times also over several days Chrony. work with 2 different bullets .

1st Round . Shooting Cold & Dirty 1st round shot .
AR ( Short barrel -10.5" ) / 300 Wispr / Suppressed .
using different powders & different weight bullets on loads .

Every Day I do Chrony work with the barrel Cold & Un-contaminated Suppressor . The 1st Round is always Hot on the Vel . w/70 fps Boost .
& if I let it sit around for while with open-Chamber on the AR with getting it cooled-off & Suppressor w/fresh cold air . It happens also .
I know Suppressors can cause Vel. Boost . But I thought is was strait across the board on your Loads & Vel. you shot . & I have had a Suppressor give Vel. Boost on a .308 but it was constant every Round fired until it was removed .
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Q- ? is :
Is this SupCan Boost or just 1st Round Dirty CB shot ? or this typical on short-barrel Suppressed CB shots ?
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