Airgun Moderator Design, Performance, and Development - American Air Arms Slayer and Brevitas (part 14)

Catch the previous episode HERE.

Perpetually short on time, I’m going to hopefully keep this one brief. Previously, I talked a bit about two projects I was working on. The first was an American Air Arms Slayer mod (two in fact), and an attempt to make the smallest and lightest moderator possible/pragmatic for the FX Crown which I nicknamed the Brevitas. This post introduces essentially nothing new, but concludes those projects.

FX Crown with Brevitas moderator

The issue with the Brevitas wasn’t one of acoustic performance, but rather mechanical performance. coming in at less than 30 grams, 74mm in length and 28mm in diameter, this was never going to be the unspoken last word in silence. That said, both on the .22 and .30 Crowns it brings the peak down below the factory performance with the shroud extended while being about half the length. But mechanical performance, what do I mean? Well the long and short of it is I wanted better impact resistance. Moderators will be subjected to baffle strikes eventually, and being on the end of your gun may just be banged into things from time to time, so I wanted better. A surprising amount of material development went into this, but I can happily say the material now out-performs ABS and Nylon on the IZOD impact tester. It also is translucent, which I think is pretty darn cool as you can kinda see what is going on inside it.

Brevitas TD FX Crown .22 and .30 (two different mods. Note traces are different scale) - 162 & 609.3 respectively

So what about the Slayer? Well the final test for that is in. The slayer is pretty violent, so I wanted to make both mods quite robust. I nicknamed them the Gladius HP and Brevitas HP because both are heavily built high power specific adaptations.

First up is the Brevitas HP. I kinda winged this design, took a few educated guesses, and went with it. As luck would have it, it ended up quieting the Slayer more than the factory mod. This isn’t a huge accomplishment as the factory design had just a couple very long tapered cones, more of a contained air-stripper than a moderator/suppressor, but wherever I can shed weight and length I’m happy, and this did that. And just as a quick reminder, the Slayer is unregulated, and so its sound signature changes considerably across the discharge cycle. The number is just an average, and the trace I pick is meant to be representative of the set, rather than the average necessarily.

Brevitas HP Slayer .30 ~200FPE - 701.71

And, finally, the Slayer - Gladius HP combo. I really was somewhere around the sound signature floor with this one. Depending on the test, the tube ping was louder than the muzzle report, which skews the average high. Never the less, I’m happy with the result and (by his comments) the gentleman who loaned me the rifle was as well. And, honestly, that is what matters most. There could be a whole massive thread on depinger design and optimization as well, but in this case these slayers are 3K$ a pop, and I didn’t want to mess with it. ~3000PSI air and potentially explosive decompression can both do weird things to materials, both immediately and over time, and the last thing in the world I wanted to do was put some crazy untested hardware into someone else’s very expensive toy which could damage it or simply make a mess. So here we are.

Gladius HP Slayer .30 ~200FPE - 526.67

That is it for now. I realize this was a bit of a quick and sloppy post. I wanted to get everything written up and and out there. This Slayer ended up being a bit of a spanner in the works, the project dragging longer than I’d have liked, so as fun and challenging as it was, I’m also kinda glad it is finished.

Where to from here? Not sure. Ideas for more small and asymmetric designs have been percolating in my mind for some time now. The Leshiy was too asymmetric, that is to say the bore was so close to the wall that serious design/performance compromises had to be made and acoustic performance was lost relative to total length/volume. But what about an asymmetric design that made no scarifies? Something more akin to the Mus, a moderator inside a moderator, except instead of pushing the limits in terms of scope clearance, that extra reflex volume could simply sit below the bore axis out of the way? And what about the little Brevitas? I made the design 28mm because that was the OD of the Crown’s shroud and smaller would look ridiculous, but the TKO I tested was much smaller diameter and there are other guns with skinny shrouds where such a design could be just the ticket. What about something like that, something to push those limits? As always I have more ideas than time to design and test them. For now, I hope this post was interesting, informative, and entertaining.