What are the piston diameter, stroke and xfer port specs for Diana air rifles?

[UnderPressure]

Here are some specs I found:

34: 28mm piston, 93mm stroke, 4.0mm x 23.5mm offset xfer port

48: 28mm piston, 1000mm stroke, 4.0mm x ? straight and non offset xfer port

54: 28mm piston, 105mm stroke, 4.0mm x ?.straight and non offset xfer port

460 Magnum: 28mm piston, 114mm stroke, 4.0  x ? straight and non offset xfer port.

350 Magnum: 28mm piston, 115mm stroke, 4.0mm x 23.5mm??? offset transfer port

Are these specs right?

Does the 54 really have 5mm greater stroke than the 48?

Does the 350 Magnum have the same transfer port dimensions as the 34?

How long are the straight non offset xfer ports on the 48, 54 and 460 Magnum? Do they all come 4mm wide ?

[Deerstalker]

This may help.
Pellet Rifle Swept Volume formula:
Rifle bore radius squared x Pi (3.14159) x piston stroke = cubed mm.  Convert to cubed centimeter by moving decimal point 3 positions left. 
Example:
HW95L .22 caliber 26 mm Bore radius = 13 squared (1/2 diameter) = 169 mm x Pi (3.14159) = 530.929 x HW95L Stroke 85 = 45,128.9 mm cubed.  Convert to CC (cubic centimeter) = 45.128 or 45.13 CC for Swept Volume.
FYI & may be in error. I have these numbers for a HW95 BUT I have not measured them.
TP size = 3 mm, length = 15 mm, TP volume = .106 cc. HW95 piston bore = 26 mm with stroke of 85 mm. Piston weight = 254 grams.

[UnderPressure]

This may help.
Pellet Rifle Swept Volume formula:
Rifle bore radius squared x Pi (3.14159) x piston stroke = cubed mm.  Convert to cubed centimeter by moving decimal point 3 positions left. 
Example:
HW95L .22 caliber 26 mm Bore radius = 13 squared (1/2 diameter) = 169 mm x Pi (3.14159) = 530.929 x HW95L Stroke 85 = 45,128.9 mm cubed.  Convert to CC (cubic centimeter) = 45.128 or 45.13 CC for Swept Volume.
FYI & may be in error. I have these numbers for a HW95 BUT I have not measured them.
TP size = 3 mm, length = 15 mm, TP volume = .106 cc. HW95 piston bore = 26 mm with stroke of 85 mm. Piston weight = 254 grams.

We could also use swept volume, transfer port volume and barrel volume to find compression ratio at various points.

To find compression ratio with pellet in breech take the swept volume and divide by transfer port volume. (Note: This is a hypothetical number as the compression ratio will never actually get this high due to movement of pellet down the barrel.)

To find the compression ratio with the pellet just before exit of the barrel take the swept volume and divide by transfer port volume +  barrel volume. Keep in mind this compression ratio assumes the piston is resting on the xfer port. If the piston is not resting on the xfer port and instead bouncing back at some point then the compression ratio will be lower than the theoretical maximum (which is piston resting on xfer port).

Here are some compression ratios for the Diana 34 EMS which has a swept volume of 57.26cc, transfer port volume of .3cc and barrel volume of 8.1cc (.177 @ 19.75" long) and volume of 12.44cc (.22 @ 19.75" long).

Diana 34 with pellet in breech = 190.1:1
Diana 34 with .177 pellet about to exit barrel = 6.82:1
Diana 34 with .22 pellet about to exit barrel = 4.49:1

[UnderPressure]

According to the chart below the 48 and 54 have the same stroke length when the same trigger is installed.

Note: This chart claims 80mm stroke for 34 compared to the 93mm I have seen elsewhere. Hopefully I will  find out what measurement is correct in the future.