6-pdr 7cwt APCBC dimensions

[wingsofwrath]

Hello, does anybody have proper dimensions for the British QF 6-Pdr 7cwt APCBC projectile?



I got a case recently and plan on 3d-printing the projectile for it, but all I have is this drawing of the US M86 on which the given dimensions don't actually match up with the drawing and contradict themselves.

 

[Eggburt1969]

Hello, does anybody have proper dimensions for the British QF 6-Pdr 7cwt APCBC projectile?

View attachment 169833

I got a case recently and plan on 3d-printing the projectile for it, but all I have is this drawing of the US M86 on which the given dimensions don't actually match up with the drawing and contradict themselves.
View attachment 169832

How have you taken the diagram dimensions; in inches or in calibres?

It's pretty common for US technical diagrams from the period to be in calibres.

If you take the dimensions as inches, then it's only 4.594 inches (116.7 mm) long, but if you take them as calibres then it's 261.9 mm (10.30 inches).

 

[Antoon]

Hereby a German drawing of he Mk 9 model

 

[wingsofwrath]

How have you taken the diagram dimensions; in inches or in calibres?

The diagram is in calibres. Here it is converted to millimetres.



However, as I said, there are some problems if you try to build a model from this blueprint because there are some differences between the dimensions given, the drawing and the pictures of the actual shell. Also, the M86 and the UK 6pdr APCBC are slightly different in both dimensions and shape, especially when it comes to the cap, which is cylindrical on the M86 and tapered on the 6pdr, so trying to make the latter from a drawing of the former is not recommended. Here is the same drawing, with actual dimensions in blue:



Moving on, here is my attempt to reconstruct the 6pdr APCBC from a picture. I matched the calibre and the driving band, since the camera is pretty much perpendicular there. I know from another source the dimensions of the driving band and crimping groove, so we had a couple of hard numbers to play with. As you go towards the front of the shell though, the distortion due to the camera angle starts to be an issue and foreshortens the image, so the dimensions derived from there are dubious at best.



Finally, here is the revised drawing, taking into account the dimensions kindly provided to us by Antoon and we get this, which I say is a pretty good approximation of the real thing.

 

[Weasel]

Hi Wingsofwrath,
The picture in your first post is one of mine, if you would like some of the other pics taken at the time to help please ask. I dont have it anymore, sold it with all my other 6pr 7cwt rounds over the last few years.
Weasel