WW2 heavy guns, your choice

an other episode, oh yes we are near to end

requirements
fire in combat in WW2
1 hour max time to ready
20 km range
40 kg shell


challengers (near all need check for time to ready, i suppose that 8 inch and larger need more time)
model/weight in fire/ range/ shell weight/ traverse/ elevations
15 K 16/ 10,7 tons/ 22 km/ 51,4 kg/ 8°/ -3°+43°
15 K 18/ 12,5/ 24,8/ 43/ 11(360)/ -2+43
15 K 39/ 12,2/ 25,4/ 43/ 60(360)/ -3+46
15 SK C 28/ 16,9/ 23,7/ 45,3/ 16(360)/ 0+50
17 K 18/ 17,5/ 29,6/ 68/ 16(360)/ 0+50
152 Model 1935/ 18,2/ 25/ 48,9/ 8/ 0+60
149/40 Mod. 35/ 11,5/ 23,7/ 46,2/ 60/ 0+45
155 GPFT/ 12,2/ 21/ 45/ 60/ 0+39
194 GPF/ 29,6/ 22,5/ 80,9/ 360 moving/ 0+37
155 M1/ 13,6/ 23,5/ 43/ 60/ -2+63

Pretty easy, The US 155 M1.

The German guns had their barrels taken out for any moves involving long distance. Only eight 15cm SK C 28 were ever mad and they used the same carriage as the 17cm K 18 and once barrel production caught up with carriage production the carriages were re-barreled to 17cm.

most of the others had problems of one kind or another.

if i'm not in wrong Shortround6 you ever choice a western allies guns (for not write a US gun)...

probably i'm going with the 17 K 18

The US guns may not have been the best at any one thing but they generally had a number of all round characteristics that put them in the top 3 in any category.
Filling out the lists with WW I left overs and limited production odd balls isn't going to change the top places.

The US used the 155mm GPF at the end of WW I as the Model 1917 and built their own as the model 1918 and used them at the start of of WW II. 100 were mounted on modified Sherman chassis to make the M12 self propelled gun. Either the US made a better gun with the 155mm M1 or they made a mistake in switching to it?

The 17cm K18 was a good gun but took longer to emplace (even if it makes it in your 1 hour dead line). It also weighed about 6000kg more on the road than it did emplaced (if WIki can be believed) due to the extra limbers and wagons needed to move the carriage, barrel and turntable. German gun has better performance but weighs about 65-68% more on the march and takes longer to put into action and take out of action.



As for the french 194mm GPF? nice idea in 1917/18

View: https://www.youtube.com/watch?v=YJfUrIrYNRY

But the gun vehicle was powered by electric motors which got their power from a generator in the second tracked chassis, The men in the video are carrying the power cables so they don't get run over. You will pardon me if i don't think this was one of the better gun movement systems in 1941?

probably is true the US gun are in the top 3 but are not the first...
the 17 cm and M1 large difference in weight in march configuration is from the fact that 17 cm march in different loads, the difference in fire is "only" 30%, the italian 149/40 is lighter of M1 but the italian had not the enough heavy tractors so need to move the gun in 2 load
so it's true that 17 cm need more time for in and out but has +25% more range and +50% heavier shell and a single vecture is lighter of the M1 so a for some aspects a better mobility

Basically your list drops to;

15 K 18/ 12,5/ 24,8/ 43/ 11(360)/ -2+43
17 K 18/ 17,5/ 29,6/ 68/ 16(360)/ 0+50
149/40 Mod. 35/ 11,5/ 23,7/ 46,2/ 60/ 0+45
155 M1/ 13,6/ 23,5/ 43/ 60/ -2+63

and the 15 K 18 is iffy.

In 'battery' or firing position is not were weight gives you trouble. It is getting the gun to the firing position that counts. Needing two (or three) tow vehicles just for the gun (without ammo) is hardly an advantage unless the roads/bridges are really crappy. Just where in Europe was the US unable to deploy the 155mm M1 gun?

sure the M1 can not deployed in my town, also today we have 12 ton bridge, same is true for the next northern town, next southern town the deployement was possible if the bridge was non destroyed fom allies bombing (now there are 2 new bridges but the original roman bridge was not rebuilt), from the other side the deployement of M1 is not possible the mountains had not roads, and i'm living not in the italian alps borders.

the 17 K 18, the 149/40, and so, were dismantled on place so the march weight has not significance, the 149/40 is 2 load a 6,5 ton and a 7,8 tons, i don't know the right weight for the 2 load of 17 K 18 but would be around 12 tons each

Personally I'm a fan of any of the German WW2 railway guns



And of course the slightly insane 80cm Schwerer Gustav