The baffles are physically thicker in the FTN series than in a traditional metal suppressor so the entire thing has to be bigger. I did find this https://guncadindex.com/detail/SuppressorPack:2 and it looks like it uses FTN baffle geometry but sealing it up in a pneumatic tube. It has can be built 5-8 inches long depending on your needs. It also appears to be bored for 223 as well. IDK how well it performs. I'll be interested in trying both of them once I don't have to pay the tax to make them.