I know its a little late, but maybe this will help someone else out.
There are two pipe burner designs I use, both usually made out of schedule 40 black iron pipe, 3/4" to 1 1/4" in diameter. One style I will drill the holes in two lines, 45* from each other along the length of the pipe. The other is to cut slots with a thin cut off wheel across the bottom edge of the pipe,
Drilling the holes will give you more of an even, efficient , and cleaner burn on the propane and I use that in the cooking chamber. A single pipe burner with a high pressure regulator will put out amazing BTU. But you have to protect the holes from grease drippings with a grease shield or they will get clogged up. So I do not use this style in a firebox.
The pipe burner with slots cut along the bottom is less efficient, you will have an uneven flame with a lot of "yellow" . But , it does not require a shield because it protects itself, so it works great for fire starters where you do not have much room and don't run it for very long periods of time.
This is a drilled 3/4" burner , it sits under a reverse flow plate so as it does not need a grease sheild either.