OldCrow - Many years ago, a company named Acerbis (sp?) made polymer, plastic, silencer/spark arresters for the off-road, 2-stroke motorcycle industry. These silencers were very effective at reducing noise, far better than anything available at the time.
I would think the application would be very similar to that of an air rifle, when considering sub-turbulent air velocities. May be worth looking into.
I’m nearly certain Acerbis stopped making silencers years ago, but the significance is; plastic-housed silencers did a superior job over aluminum housing for quieting dirt bikes back then, and quieting a 2-stroke engine is not that unlike an air rifle. So the perforated core-tube and packing used then and still used now, may work well.
Nice design , i to have been working on these with a friend , made a larger one , and it really had no difference in sound than a smaller one? We asked ourselves why ???? Well , we started to add a special sound deadening fiber material in between the baffles and the outer shell. We drilled holes to slow air yo leak into this fibrous chamber and you now what ??? It worked fantastic . The plastic as is was just making a sound chamber that transferred the sound outside , the material now deadens this and the bigger can we make , now the more quiet the outcome !!!! Hope this helps !
Wow! That is way cool…that reminds me of biological construction, like an organ or sponge or perhaps insect nest.
I'm LATE to this conversation and after a skim read, thought I would just add one thing I've discovered in 10+ years of making LDC's.
Supersonic speed air leaving barrel behind the pellet or slug that is going slower ... Can and will overtake said projectile and when this air gets ahead of said projectile the disturbance created within the LDC is great & having the projectile pass threw this turbulence will destabilize it !!! Isolating levels that somewhat keep the air from overtaking the projectile as it passes down the LDC's length work best IMO.