DIY moderator increases velocity 35 feet/s compared to HOGAN

Hi everybody
I am a new member, Nikos from Athens Greece 63 years old, retired. Own a .25 cricket stock. I have been reading a lot in this and other forums and this is my first post since my knowledge is limited, just learning. Well anyway i had a hogan decimeater which i put on the cricket and used this for a while.
A couple of weeks ago i went to a friend with a lathe and made an aluminum one, 28 by 4 cm (external) simple design with 4 metal washers with a hole of 7.2mm, and hair curlers wrapped with foam. I decided to compare the two moderators using the android program Sound Meter. i did not care how accurate it is, since i only wanted to measure the difference in db shooting the cricket stock, then with decimeater mounted on the stock shroud and then with the diy moderator mounted on the stock shroud. I also measured the speed in ft/s. To make the long story short, the diy moderator produced 67 db and 978 ft/s the hogan decimeater 72 db and 944 ft/s and the stock 77 db and 940 ft/s. i did the test 5 times and the diy fluctuated 4-5 db lower and 31-35 ft/s over the hogan.
So my question is how can a moderator be more effective in reducing sound and at the same time increase velocity.
Thank you all, be good and healthy

edited: ps. forgot to mention that when i was measuring the db in all occasions i was not using any pellets. the barrel was empty.