I previously pushed Kodak T-Max 400 (135 format) to ISO 1600 by using dilution B (1+31) of Kodak HC-110. The results were okay but not perfect. I compare the results to Kodak D-76 (1+1) which I used during the summer. HC-110 didn’t perform as good as D-76. I have used a lot of Agfa Rodinal but I’ve tried only once to push T-Max with it (ISO 800 in 1-hour stand).
Someone told me to use HC-110 in another dilution (unofficial H, 1+63) and I also found a great Rodinal 1+25 recipe to try. So, I shot a test roll of T-Max. At first I thought I would shoot the roll with repeating same frame (same settings, same focus, same composition, on tripod of course), cut the film in three parts and develop each part differently. It would have made the test more stable and “scientific” but I wanted to see how the results would change if the subject or the camera settings were different. So, here’s what I did. I quickly shot 14 frames around the house with Nikon F100 and AF Nikkor 50mm f/1.8D in aperture priority mode and marked down the aperture value and the subject. Then I shot 8 frames more freely (the cat was there so I took photos of her) and marked down the aperture values. And then I shot 14 frames again, of the same subjects with the same aperture values as before to get, at least, very similar photo pairs. The pairs were taken within 10 minutes of each other. In the darkroom I cut the film in two pieces and put one part into one tank and the other part into another tank.
Development notes: The first half of the film was developed in Kodak HC-110, dilution H (1+63), for 18 minutes in 20°C. The tank was agitated the tank for 30 seconds and then one inversion every minute. The second half of the film was developed in Agfa Rodinal 1+25, for 12 minutes in 20°C. The tank was agitated slowly/carefully for 30 seconds and then one slow inversion every minute.
Both parts of the film were scanned and post-processed similarly. I used SilverFast SE software with Negafix set to Linear (no film profile used), and scanned at 2400 dpi without auto sharpening. In Photoshop I desaturated the frames (they had purple tint), cropped off the edges and removed the largest dust spots. No other post-processing was applied.
Here are some of the photo pairs (do not mind about the lack of proper contents). The HC-110 example is always on the left, and the Rodinal example is on the right. Click to enlarge.

Aperture: f/4

Aperture: f/2

Aperture: f/16

Aperture: f/1.8
The last photo pair is from the eight frames I took in between the real pairs.

Aperture: f/1.8
The photos are small but can you tell which are your favorite? I like the Rodinal photos more because the contrast is (in my opinion) more balanced. The HC-110 photos are not bad either, for example in most of the HC-110 photos the black parts are darker, thus better. HC-110 dilution H is clearly much better than dilution B for pushing.