Hi Aaron and welcome. The Springfield threaded barrel is .5 x 28 tpi. I recommend the Gemtech Lunar: https://midwestshootingsupply.com/product/gemtech-lunar-pistol-suppressor-9mm-300-blackout-5x28-thread-12711/ ------------- Cheers and stay safe!

There is a large variety of compatible suppressors for the Echelon as almost anything intended for 9mm will work, or larger calibers like .45 also work and can add interchangeability with other guns in case that's desirable. Since the Echelon is a tilting barrel design you will need a piston and booster mount (AKA Nielson Device) in order for it to cycle reliably, and the piston is what you need to find in 1/2x28 TPI thread (same as 0.5x28). While I see basically no compatible suppressors in stock here, I'll give one example as the SilencerCo Omega 9K which is a 9mm suppressor that includes includes the booster assembly already and then just requires a piston such as this one: budsgunshop.com/product_info.php/products_id/1453/silencerco+osprey+octane+piston+.5x28+9mm+stainless+steel />While not an exhaustive list, some other generally reliable manufacturers of 9mm suppressors are Dead Air, Rugged, Griffin Armament, Gemtech, B&T, and Yankee Hill Machine.

.5x28 is the same as 1/2x28 TPI. Any silencer that has that thread pitch and caliber designation will work. It boils down to your budget and your preference.