August 1944: Arthur and Michel feel explosions from 170 miles away (variations on a theme)

Here is an example where my grandfather's account, and Dr. Planas's account perfectly match.  On August 15, 1944, during Operation Dragoon, both men felt the explosions of the coastal artillery from about 270 kilometers (168 miles) away.

340mm/45 Modèle 1912 gun. 
The diameter of the projectile was more than 13" across.

        On August 15, we hear in the distance many roars of aircraft engines and in the calm of the atmosphere of a region where there were practically no trains or cars, we hear huge distant detonations. The message of 12:20 p.m. told us of the Allied landing and the detonations were those of naval guns and aerial bombardments. The days of August 16 and 17 unfold like a dream, in the constant comings and goings of liaisons with the Departmental C.P. [Command Post] and with neighboring units, the departure and arrival of patrols which monitored the movements of the enemy. --Dr. Michel Planas, 1955

I have heard the personal message on the radio and allied troops landed on the beaches of Southern France. This secondary episode for a Second World War historian, was for me the greatest, the most important fact, the one which undoubtedly saved my life.   All night heavy navy guns could be heard firing somewhere 150 miles to the South. But the deadly small firearms noise ceased in the mountains around and elated joy filled the survivors’ souls. --Arthur Lubinski, 1974

        A few days later, a week later, there was the landing, the subsidiary landing in southern France on the Mediterranean, in Fréjus, if I remember correctly, Fréjus. And we, in the mountains of Vercors heard the heavy navy guns. How many? One hundred sixty miles away. One hundred sixty miles away, and we heard over the mountains a booommmm, boommmmm of the heavy navy guns. Well, all right.  --Arthur Lubinski, 1988

To understand the distance, Arthur and Michel were in the vicinity of Châteaudouble, Drôme, France. The secondary landing in Operation Dragoon came from the Mediterranean, concentrating on the southeast portion of the French coast, adjacent to Italy, and yes, Grandpa did remember correctly, Fréjus was right in the middle of that area. Google Maps tells me that that is 270 km away.  For comparison, I show the actual locations on the French map, as well as two locations in the United States that are similar in distance.

Fréjus to Châteaudoble - about 270 km (168 miles)

Imagine being in Trenton, NJ, and being able to feel explosions in
Washington DC. Note Trenton's proximity to NYC. 

Still... being able to feel explosions from 170 miles away?  It's hard to imagine the size of the explosions and the guns that have that produce that kind of power.

Wiki tells me this about the German defenses during Operation Dragoon:

Along the coast, about 75 coastal guns of heavy and medium caliber were placed. Toulon was protected by a complex of heavy 340 millimeters (13 in) gun artillery batteries in mounted turrets. After their military take-over in November 1942, the Germans improved the coastal defense further by repairing damaged and outdated turrets, as well as moving in additional guns. This included the 340 millimeters (13 in) guns taken from the dismantled French battleship Provence.

These guns were massive:

• Weight: 270 tons
• Total length:  33.6 m (110 ft)
• Barrel length: 15.3 m (50 ft)
• Shell: Projectile plus charge combined: approximately 465 kg/1000 pounds. It used a separate projectile (about 700 pounds) and charge (bag of explosives weighing about 300 pounds).

340mm/45 Modèle 1912 gun converted to railway mount.

340mm/45 Modèle 1912 gun taken from the Battleship Provence,
and mounted on an existing turret along the French coast.
Note the soldier standing on the ground in front of the barrel.

340mm/45 Modèle 1912 guns when they were still aboard the Provence.

It was loaded with hoists or small cranes, and could fire a round every 30 seconds or so. The area behind the gun held about 8 rounds, so I think it could fire every 30 seconds for 4 minutes, before needing to be "re-loaded." If the hoists weren't working properly, a crew of eight men could manually work the hoists, and then it took seven minutes to load and fire it.

So ... yeah.  Hearing and feeling the guns 170 miles away? I think I believe it.

Bibliography: 

• Planas, Michel. History of the 4th Company 2nd Battalion FFI of Drôme or; Three Doctors from the Same Family in the Maquis. 1955
• https://en.wikipedia.org/wiki/Operation_Dragoon
• https://en.wikipedia.org/wiki/Operation_Dragoon#Opposing_forces
• https://en.wikipedia.org/wiki/340mm/45_Mod%C3%A8le_1912_gun
• https://en.wikipedia.org/wiki/Canon_de_340_mod%C3%A8le_1912_%C3%A0_berceau
• https://en.wikipedia.org/wiki/Canon_de_340_mod%C3%A8le_1912_%C3%A0_glissement
• https://en.wikipedia.org/wiki/French_battleship_Provence
• https://explorabilia.co.uk/2019/07/13/batterie-plouharnel/ <--lots of cool pictures, and even includes a cool old video.
• http://www.navweaps.com/Weapons/WNFR_134-45_m1912.php <--lots of detailed info about the guns.