Rocket oven not getting hot enough

Used a mixture of oak, pine and Cyprus twigs for fuel. Oven only got up to 295 degrees f. Inside the oven, placed a small wire rack with volcanic rocks piled on top to capture heat. Rack is setting raised over the riser opening. Opening is aprox. 2 1/2" x 8" close to the back of oven. Oven door is 2 1/2" thick wood. The entire burn chamber and riser is insulated with perlite and cement, 2 to 3 ". After it was drawing good I turned down the damper to 1/4 open to retain some heat. The chimney comes down into the oven by aprox. 8". Again trying to retain heat between the top of oven and chimney opening. The only thing I can think of is to use ALL hard wood. Wouldn't think that would make that big of deference. Any input or suggestions are greatly appreciated. It needs to get HOTTER than 295. f

Hey Ray!
I haven't built a rocket oven but I see some things about your build that might be keeping you from getting high temperatures.
You mention a 2 1/2" by 8" opening.
If your core and riser match that, they are not within the standard design parameters.
A circular or square cross section of at least 4" is recommended, and 6" or larger is preferred.
The diagram you share shows the firebox as long or longer than the riser is tall.
The prefered ratio for a J tube rocket is 1-2-4, with
1 being the height of the feed tube, 2 the length of the burn tunnel and 4 the height of a riser.

Your feed tube seems to be slanted, which might reduce the turbulence that happens where it meets the burn tunnel.
More turbulence tends to be better for complete combustion.
The riser seems to have a slanted portion, I'm not sure how that would affect things, I think Matt Walker experimented with a "broken" riser design,  but strait is the standard.

You don't mention what kind cement you used for insulation, nor the ratio of perlite to cement.
Portland cement will begin to fail at 482 degrees fahrenheit.
The higher the cement to perlite ratio, the less insulative it will be.

I would try a fire inside the oven itself,  along with firing  the existing rocket .
You might be producing unburned combustion gasses in the rocket stove which in turn could feed the hearth fire.

Yea, the drawing is not to scale. It's just a rough rendering. The 2 1/2 x 8 opening is aprox. 2" long. It's tapered down from a 6" square riser. Drawing did not reflect this very well. But below the slanted opening the J tube is within 1/2" or less of meeting the preferred 1 - 2 - 4 ratio. I'm with ya on the slanted portion. I was trying to maximize the cooking / floor space.
Feel pretty good about the cement and insulation. used Hi-temp cement and hi-temp blocks. The outside surface never got the slightest bit warm. Not sure what the ratio on perlite to cement was.
Like idea of doing a fire inside the oven. Look forward to trying this. Thanks.