Naturally aspirated (NA) burners are very subject to malfunction, or poor function due to extremely small variations in their assembly and geometry. The alignment, position and size of the gas orifice is arguably the most critical aspect of the burner design. The best burner designs, IMHO, have either this geometry well tested and "locked down" or have the ability to modify to allow tuning (i.e. slides to allow moving the burner orifice up and down the mixing chamber, replaceable orifice parts to allow easy orifice size changes, movable shrouds for air inlet...). Your burner design does not appear to have any ability to be easily tuned and is an untried design for the size of forge. I'm not familiar with the Bear River forge burner video and don't know how much detail he goes into regarding construction in the video, or if you just followed what you thought was the design based on viewing it in a video of him working.
I'm afraid that unless you get lucky on a first time trial that you are in for some disappointment. Please note that NA burners can be both too small and too large for a forge and will behave quite differently burning in free air than in the forge proper.
By all means test your burner, but please be careful. You will need a properly designed gas train with a good 0-30 psi propane regulator (preferably with a gauge), and not just one from an old propane barbeque, and a 1/4 turn gas rated ball valve to allow you to shut off the gas quickly in case of trouble. Please don't try to use just the propane tank valve as a device for safety shutoff and metering.