This first picture shows (from bottom to top) the standard kit gun, the Jordi Rubio 12.8 cm Pak 44 for the Huntng Tiger or Maus barrel, and then the JB Model 17 cm Kanone Gerschutzwagon Tiger barrel. They are placed at the distance they would protrude out of the mantle. I'm using the 17cm one to make it look like a 15cm one. In 1/35 scale the size difference shouldn't be that noticable plus I love the perforations on the brass muzzle brake. It's the main reason I bought it. I may not use the second section of the 17cm barrel shown. I may just use the first part.
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Image 2 shows the Dragon turret on top of the 17 cm gun
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The last image shows the turret with the JR barrel but with the kit muzzle brake. Either way it's going to add 1 to 2 inches to the overall length of the barrel from the original kit one.
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Comments always welcome!!