It would be cool to see more things that function like the FG42 being open bolt FA and closed bolt semi.
Three that I know of:
1. Geoff Herring (Inventor of the Shrike) has one but I don't know if he ever released it:
http://www.smallarmsreview.com/display.article.cfm?idarticles=2249
"Ares Defense has designed a few of their own trigger systems to work with their upper receiver to permit open-bolt fire in the “FULL” position when installed in a registered lower receiver. Because the Bureau of Alcohol, Tobacco and Firearms (BATF) has ruled that an open-bolt firing mechanism installed in a semiautomatic-only firearm manufactured after 1981 would be a machine gun in and of itself, they designed these only to fit registered MIL-spec lower receivers. The first variation produces an open-bolt “SAFE-AUTO” function. The second variation produces a closed-bolt “SAFE-SEMI” and an open-bolt “AUTO” function. These will both be available as accessory options for those with approved Form 4’s or an FFL/SOT."
2. LWRC's M6:
https://www.tactical-life.com/firearms/lwrcs-multi-mission-battle-rifle/
"As a semi-automatic, it functions as a typical closed bolt rifle. If you toggle the selector from “semi” to “open bolt automatic,” the rifle’s bolt remains closed for the first shot, increasing ignition probability to 99.7 percent, allowing the infantry automatic rifleman to take point on patrol, initiate an ambush, or be the first through any door. After that first shot, the weapon reverts to an open bolt, allowing light-automatic fire support. When you release the trigger between strings of fire, the bolt remains to the rear, allowing convection air cooling of the barrel and chamber area. When you pull the trigger again, the bolt closes and fires continuously until the trigger is again released, with all the advantages of an open-bolt machine gun. To go back to closed bolt, semi-automatic fire, the operator switches the rifle’s selector back to semi. The bolt closes and chambers a round, but does not fire. When you pull the trigger, you get single shots with each pull. This offers all of the advantages of both types of systems with the disadvantages of neither."
3. Lastly, Jim Sullivan did it also but not sure about the required modfications:
https://www.youtube.com/watch?v=gOUKXIrDE0I
I don't know of any out in the 'wild' for people with transferrables and even if they were out there, I wouldn't want to be the guinea pig to see how it holds up long term.
Any M16 open bolt system would require specialized fire control and carrier. For me, I like the ability to quickly swap uppers for pistol calibers or whatever. I wouldn't want to give that up just for open bolt or even want to deal with the hassle of swapping out the firecontrol. As a C2, sure why not and just have a dedicated postie lower but not as an individual.
Getting a slow RoF is not hard but getting it to be smooth is kind of subjective.
I find the configuration to below to be bouncy but one of my friends loves it. He is the only one though. Everyone else hates the way it feels. 474 RPM
I much prefer this setup with the same upper. 636 RPM
What I've been trying to do is to get a slow cyclic rate in a shorty and retain smoothness.
Below is pretty smooth. 589 RPM.
I've got a lot of data just not enough time to document it all on my site.
