I will email you a copy of the tables. The guns did and could fire at 10degrees and record hits on targets.
The AnXI 24-pdr howitzer had a shorter range overall than the porte Longe, but was more accurate. The gribeauval 6.3pouce was the least accurate.
Given the howitzers did not hit the target area beyond 6 1/2 degrees, no data for the accuracy was collected, it does not mean though that they did not fire beyond this. 15degrees seems to have been the maximal operating potential of these guns before they were rendered inoperable. Higher degree of elevation would be possible with field works, use of reverse slopes etc.10degrees was the maximal elevation for the field guns.