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I put a plenum extension on my .25 cal. with the expectations of gaining power but did not gain any power. If you are expecting a power gain don't waste your money. Tried contacting Ernest about the failure to increase power but no response. The reason I bought the plenum extension is because of his claim it would give a 30-45 FPS increase with out any increase to regulator pressure. Was trying for more power to test some slugs. Max velocity before plenum extension was 920 FPS. Max velocity after plenum extension is 920 FPS. Regulator is set at 145 Bar.
That’s strange but I did port the firing-valve a bit too, nothing major though. I was maxing at 940 fps with 33.95 grainers when my reg was at 142 bar.
Did you adjust your hammer spring and find your max after the plenum install?
I have ported my valve some and polished the transfer port. Yes I did adjust my hammer sping to max after install. My max velocity is when hammer spring is at max just before the gun won't cock.
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