USA

• T57
  • 76 mm Gun (M1918): 520 m
• M37
  • 105 mm Howitzer M3: 440 m (480 m HEAT)
  • 105 mm Howitzer M4: 960 m (1100 m HEAT)
• M7 Priest
  • 105 mm Howitzer M3: 380 m (420 m HEAT)
  • 105 mm Howitzer M2A1 905 m (875 m HEAT)
• M41
  • 155 mm Howitzer M1: 1210 m
  • 155 mm Gun M1918M1: 1210 m (1315 m M101M2)
• M12
  • 155 mm Gun M1918M1: 1210 m (1315 m M101M2)
  • 155 mm Gun M1A1: 1315 m
• M40/M43
  • 155 mm Gun M1A1: 1315 m
  • 203 mm Howitzer M1: 1175 m
• T92
  • 240 mm Howitzer M1: 1250 m

German

• Bison
  • 15 cm sIG 33 L/11: 465 m
• StPz II
  • 15 cm sIG 33 L/11: 465 m
• Wespe
  • 10.5 cm leFH 16 L/22: 1000 m
  • 10.5 cm leFH 18 L/28: 1000 m
• Grille
  • 15 cm sIG 33 L/11: 355 m
  • 15 cm sFH 13 L/17: 710 m
• Hummel
  • 15 cm sFH 13 L/17: 1210 m
  • 15 cm sFH 18 L/30: 1260 m
• GW Panther
  • 15 cm sFH 18 L/30: 1260 m
  • 15 cm sFH 36 L/30 Ausf. 1943: 1400 m
• GW Tiger
  • 17 cm K72 (Sf): 1315 m (1200 m Ausf. G)
  • 21 cm Mrs 18/1 (Sf): 1170 m
• GW Typ E
  • 21 cm Mörser 18/2: 1170 m

French

• Renault BS
  • 76 mm Schneider: 450 m
• Lorraine 39 L AM
  • Canon de 105 court mle 1935B: 775 m
  • Canon de 105 court mle 1934S: 840 m
• 105 leFH18B2
  • 105 mm leFH18 L28: 1000 m
• AMX 105AM
  • Canon de 105 court mle 1934S: 845 m
  • Canon de 105 mle 1930 Schneider AM: 1000 m
• AMX 13 F3 AM
  • Obusier de 155 mm C mle.1917: 1100 m (1210 m H1A)
  • Canon de 155 mm de 33 calibres: 1250 m
• Lorraine 155 50
  • Obusier de 155 mm C mle.1917: 1250 m
  • Obusier de 155 mm mle.1950: 1200 m
• Lorraine 155 51
  • Obusier de 155 mm mle.1950: 1200 m
  • Canon de 155 mm L GPF: 1300 m
• Bat Chatillon 155
  • Canon de 155 mm: 1295 m

Soviet

• SU-18
  • 76 mm Howitzer mod. 1927: 550 m
• SU-26
  • 76 mm Howitzer mod. 1927: 550 m
  • 76 mm Howitzer mod. 1903/30: 520 m
  • 122 mm Howitzer mod. 1930: 635 m
• SU-5
  • 76 mm Howitzer mod. 1903/30: 520 m
  • 122 mm Howitzer mod. 1930: 635 m
  • 152 mm Mortar NM mod. 1931: 600 m
• SU-8
  • 122 mm Howitzer A-19: 890 m
  • 152 mm Howitzer ML-20 mod. 1931: 920 m
• S-51
  • 152 mm BR-2: 1140 m
  • 203 mm B-4: 1230 m
• SU-14
  • 152 mm BR-2: 1295 m
  • 203 mm B-4: 1210 m
• Object 212
  • 152 mm BR-2: 1315 m
  • 203 mm B-4: 1225 m
• Object 261
  • 180 mm B-1-P: 1460 m

— Source: SPG gun range - General Discussion - World of Tanks official forum

With version 8.8 released in September 2013 there is now a 'Missions' button on the main garage interface that tracks tour progress.

In addition the post battle report now also shows your mission progress when relevant.

It's in the release notes:

Significantly expanded the functionality of missions. An interface with description and current mission status has now been added to the client.