You might be able to get blank tubes from these folks. Hasting barrels

http://www.hastingsbarrels.com/#:~:text=The%20Hastings%20Metro%20Barrel%20is%20ported%2C%2012ga%2C%2032-inch%2C,choice%20for%20sportsmen%20pursuing%20quarry%20in%20suburban%20areas.

Track of the wolf carries 20ga barrels, you might want to contact them for a source of 12ga barrels

https://www.trackofthewolf.com/List/Item.aspx/655/1

Last edited by oskar; 08/13/21 12:51 PM.
After the first shot the rest are just noise.