My understanding is all FAC UK and High Power ( USA ) Impacts now come fitted as standard with the Power Plenum.
UK Sub 12 and other restricted countries will receive an Impact without the Power Plenum.
To be clear - power over 12Ft Lbs - Plenum onboard - Below 12 Ft Lbs no Plenum.

If your buying FAC then YES - your RFD can speak with the distributor and ensure a new FAC Impact comes with the Power Plenum factory fitted.

Sub 12, it's going to make no difference so no need to fit it.

Hope that helps.

G

Thanks but I think we need some indepth test/reviews of Power Plenums for sub 12 users and do some side by side testing (with and without) - I have a 17cc plenum on a dreamline and I have tuned it to sub 12, by lowering my regulator to about 45bar.

This has saved me about 15 bar which means more shots per fill.

So for sub 12 the plenums can be regarded as efficiency plenums.

I am just down the m4 from your if you want to borrow mine.

apparently the maths don't work on sub 12 with power plenum

Here are the maths from my first experiment on a DL with 1X 17cc plenum

I am getting 242 shots from a 230bar fill in .177 with my reg set to just under 50bar 11.9FPE

Granted the last 8 shots were dropping off.

And it was razor sharp on accuracy all the way up to 60yrds

I am waiting on a 177 dual port breech (Huma) which should permit 40-45 bar for the same power and more shots.

How’s the experiment going ??