Sounds like it needs more fuel. Try using 3 to 4 splits instead of chunks. Make sure the splits are burning before you close the door.then prolly add 1,2 splits every 30-60 minutes. Just my guess.
BBQ is just smoke and beers!
Usually more beers than smoke.
I believe there are couple of things that could cause this. First being the air intakes on your FB and the stack size. Was a pit calculator used to calculate the size of both? Did you try opening the door a little to see if it helped raise the temp? Another thing to look at is your fuel. How much charcoal did you use vs wood? Also how dry was the wood?
Remember that by volume, wood has 30% less heat output than charcoal ….
And on the eighth day God created barbecue …. because he DOES love us and he wants us to be happy.
Current smokers: Egor (trailered RF) and Easybake (tabletop pellet drive)
I can tell you this for a fact if your firebox, intake, and exhaust are sized right then you should absolutely have no problem that cooker should at 250Degrees in 40 minutes. I built a cooker for a guy recently and I fire them all up myself and generally season them I took the cooker up to 400 degrees easily. He text me and said he was having a problem with getting up to temp. He sent a picture of the firebox crambed with charcoal and lump. I text him back and said...... get that charcoal out and put wood in it a reverse flow smoker is made for wood "it is called a stick burner for a reason" Well he did exactly what I said do and in a few minutes he was busting 300 degrees. It does not take a lot of wood but a stick burner is designed for wood. I usually take one basket of charcoal lit put it in the cooker then I add a half basket unlit to that then some small splits. when you are up to temp, simple as this feed it regular with small splits. Now cabinents may run off charcoal but..... horzintal reverse flow made of tanks and pipe are respectively Called stick burners for a reason..... they burn wood!!!!! Now clover ridge is right your wood has to be good, not old, wet and out of date!!!!!!!