Black Powder AR15

[Moonpie]

A BP power semi would be difficult to keep running.
Problem is BP fouls at different rates depending on quality of powder, amibent moisture, etc.
With that much variation it would next to impossible to keep one running for more than 3-5 shots.
With BP you need really thin brass to get gas sealing in the chamber. Modern brass is quite thick and at the low BP pressures it doesn’t expand and seal well. The blowback and resulting chamber fouling is another factor that will cause feeding issues.
It could be done with correctly made ammo IMO.

 

[grasshopperglock]

I believe a self cleaning piston system could be made to deal with the fouling going through the gas port.

As for fouling inside the barrel...The first thought is paper patch bullets. I believe paper patch is better with barrel fouling verses a unwrapped bullet skidding across burnt gunpowder residue.

The recoil spring and recoil weight would need adjustments. The explosion is happening slower. There would seem to be a timing aspect. Enough spring to allow time for the black powder pressure to build but at the same time. Allowing it move rearward, out of battery, on time with the combustion of the slower propellant.

 

[grasshopperglock]

On the self cleaning piston.

Imagine two disc with a small round rod connecting both and protruding on the outside of one of the disc.

Now picture the connected disc inside a bore. On the side of the bore is the gas port.

When the round is fired. The gas builds up between the two disc and forces it rearward to cycle the action.

Here's the cleaning part. The disc closes to the action is the disc the gas acts upon. The disc towards the muzzle end. Follows the first disc backwards. Scraping powder fouling from the gas piston bore during the movement back.

Of course there might be a need for extra port holes dealing with the gas piston bore. Enough room to get rid of the powder fouling. A design that allows the two disc piston to be forced backwards with gas hitting it on the side.

It can be done...

 

[grasshopperglock]

On the self cleaning piston.

Imagine two disc with a small round rod connecting both and protruding on the outside of one of the disc.

Now picture the connected disc inside a bore. On the side of the bore is the gas port.

When the round is fired. The gas builds up between the two disc and forces it rearward to cycle the action.

Here's the cleaning part. The disc closes to the action is the disc the gas acts upon. The disc towards the muzzle end. Follows the first disc backwards. Scraping powder fouling from the gas piston bore during the movement back.

Of course there might be a need for extra port holes dealing with the gas piston bore. Enough room to get rid of the powder fouling. A design that allows the two disc piston to be forced backwards with gas hitting it on the side.

It can be done...

Scratch that. A single disc piston that upon returning from recoil. Over travels forward within the bore. In theory removing excess fouling from the piston bore wall. A simple one way value/exit for the fouling to leave the piston bore.