Yes, the varrous “bump fire” stocks are enjoyable to shoot, but they have limited practical utility. With one pushing the weapon forward, maintaining aim (which is usually accomplished by pulling the gun to the rear) is pretty much out the window.
Fostech Outdoors, known for their Origin 12 shotgun has been hard at work pushing the letter of the law to its limit. Their fire and release trigger, known as the “Echo” trigger incorporates a major feature that the previous offerings like those from Franklin Armory have debuted.
The crux of the pull on fire and release triggers has been the propensity of them to have “hammer follow” malfunctions. Shooters of the systems have been able to pull and release the trigger faster than the bolt carrier would return to battery. While this can be slightly alleviated by using lightweight parts, it can sacrifice some reliability.
The Fostech Echo system seeks to correct that by incorporating the use of a sear, much like that in a fully-automatic firearm. The instead of releasing the hammer, the sear is used to engage a second disconnector which ensures the hammer is not released until the carrier is back in battery. In short, the gun cannot have a hammer follow malfunction.
Release is set for later this year, but triggers are starting to show up in the wild. Tim from Military Arms Channel get his hands on one of the few near production models in the wild.