by DZSabre 

28mm (1/56 scale) QF 25PR artillery gun.

You can see in the photo of the printed model how it differs from the source design and how it compares to 28mm infantry.

The model is split into three pieces to make it easier to remove the support structure and print the gun shield more smoothly. Note the gun and carriage are angled to the gunshield is verticle to make it easier to print and minimize the complexity of the supports.

The two struts from the center of the turntable align to the inside edge of the bracket under the center of the gun carriage tail.
After printing assemble by gluing the gun to the axle and let completely dry. Then, glue the two braces with one end next to the center of the turntable and the other end to the underside of the gun carriage in front of the crossplate in the middle of the frame.

Print Settings

Printer brand:

Creality

Printer:

Ender 3

Rafts:

Yes

Supports:

Yes

Resolution:

.08mm layers .4mm nozzle

Infill:

20%

Filament_brand:

Hatchbox

Filament_color:

Gray

Filament_material:

PLA

Notes:

Be careful when removing the supports from under the frame. The seat can be fragile if too strongly connected to the supports. This model does require supports

How I Designed This

Resized and shifted

The original design by Kpi1986 was about 30% too large compared to the actual length and width of the real thing. So the first thing to do was shrink it. However, the gun was also mounted too far forward and the gun shield is too far from the wheels. I had to cut the design and shift the frame back so the proportions matched photos of the real thing. I then moved the breech forward and lengthened the barrel, introducing a thinner forward section of the barrel. Some of the details became too thin to print or very fragile and I had to beef them up. These include the spokes and inner rim of the turntable, the angles braces under the gun carriage, the elevation wheel and the seat post. I also had to double the thickness of the gun shield. Finally, I modified and shortened the length of the carriage frame and angled it appropriately.