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The maximum effective range of the Hotchkiss 25mm is 3km. Taking into account the height of 1800m, this gives a ground distance of 2.4km.
Drawing a circle 2.4km from the anti-aircraft battery gives the area where the Thunderbolts would have been in range. The path taken by the thunderbolts where they were in range is 3.48km wide.
The time taken to cross this distance is 26 seconds at 300 mph or 20 seconds at the Thunderbolts normal cruising speed of 390 mph.
The effective firing rate of the Hotchkiss is 220 - 260 rounds per minute but it only has a 15 round magazine. Changing the magazine lowers the effective firing rate to 120-150 rounds per minutes
Assuming 135 rounds per minutes
An airspeed of 390 mph (so 20 seconds in range)
The battery had time to shoot 45 shots per barrel. The battery had two barrels so 90 rounds is possible.
The report says the battery fired 86 rounds so this seems reasonable.
The circular map tool is from Mappy
Note: The map is from 2023 and shows the 3 bridges over the Loire but in 1944 only the middle one was present.
The map from the Bundesarchiv says it was a 5 second burst. I've calculated more accurately for 1 barrel
A burst of 15 shots per barrel at 240 (average of 220-260) shots per minutes takes 3.6 seconds (so 4.1 shots per second)
Each barrel requires 9 magazine changes per minute, dropping the effective rate to 135 shots per minute so we've lost the equivalent in time of 240-135=105 shots. At 4.1 shots per second this is 25.6 seconds per minutes lost to magazine changes. 25.6 seconds / 9 gives us 2.84 seconds to change a magazine.
Doubling the shots to account for the two barrels, 90 shots could be delivered in 16.4 seconds in three bursts of 30 shots. Again, the Germans are claiming 86 shots.
So, ok for the guns, the range, time available and firing rate are ok. The elevation of the gun here is 37° and the Hotchkiss can do -10 to +85°.
The German map has some timings on it that can be analysed:
The map shows the 4 Thunderbolts arriving from the north-east at St. Claude de Diray at 7:23pm. They're in range over Blois town centre at 7:25pm and Lt Jenkins crashes at 7:29pm.
The distance from St. Claude de Diray to the town centre is 6.38km (3.73 miles), slightly longer if its not a straight flightpath. Two minutes to cover the distance is 191kmph (119mph) which is very slow.
The town centre to the point of impact is 8.1km (5 miles). Four minutes to cover the distance is 121kmph (75mph) - the Thunderbolt has a stall speed of 185kmph (115mph) so the times between events are too long.
If the speeds were correct, then the aircraft would have been in range for as much as 65 seconds which is a lot longer than I've indicated and would have been much easier to hit. The aircraft might have been slowly if they were looking for targets but 120mph does seem very slow. I suspect the times on the map are an approximation - there's an inconsistancy in the number of shots fired (68 not 86) and this is perhaps only intended to a sketch to illustrate the facts.
Page 9 of the German report says the Thunderbolts arrived at Le Breuil airfield at about 7pm so they spent about 23 minutes targeting and bombing prior to these 4 aircraft approaching Blois.
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