OK, sound meter is working a little better, but still do not have full confidence in it. I set the sound meter 3' in front of the muzzle, and it is about 6" bellow the path of the pellet.
First, a little about this Prod. It has had a Mrod 22 cal barrel added to it, with a custom MM 18" shroud. This shroud length was chosen for minimum length, and only has a small air space in front of the air stripper, just like a stock Prod. It is tuned to 25fpe with 18.1g JSBs.
With the Hill LDC the gun length is equivalent to the Mrod.
Close up:
Testing: with just the stock shroud, it is relatively loud, especially in my basement range. The MM shroud ext provided about a 2-3db lower report. The hill LDC produced 2-3db lower than the MM SE, or 4-6db over the shroud by itself. While these numbers do not look like a significant difference, it a very plain improvement to your ears.
My testing so far, has already earned it a "recommended" rating.
In fact, it may not find its way back into the return shipment!
This LDC does the job for what most power tuners would go for in a Prod. If time permits, I will test this on my 1720T which has a Mrod shroud on it.
Side note 1: For those looking to add a Mrod barrel to the Prod, contact Tim. He has another possible solution that you may be interested in. It retains the Prod shroud without having to buy a custom one (like I did), and adds more Mrod diameter air space, and has vents back into the Prod shroud.
Side note 2: I did try the crosman gen II baffles, but was not able to get good readings. Subjectively it seemed slightly quieter with Tim's baffles.