Stroke lengths, TP sizes and SCR for various springers...

[T 20]

Are you sure HW 35 transfer port lengths are correct as the quoted length is about an inch?

Yes, I'm sure, the HW35 transfer port is about an inch long.

[harvey_s]

My 99s had no piston weight fitted...(bought new 2020)

Did some have them fitted? If so, I wonder how they decided which ones to fit them to...

[TonyL]

As far as I'm aware the HW99 has never had a piston weight fitted as standard. I own two and have assisted in the minor fettling of a couple of other 99s. Not sure if any of them ever had the washer down at the front end of the piston as some HWs reportedly had / have? My guess would still be a "no", though......

[TonyL]

Some excellent information gleaned from the GTA Airgun Forum and Airgun Warriors. Should come in handy for some (and interesting for all springer enthusiasts).

Apologies if there are any duplications and the information is a little more abbreviated, so no piston weights / transfer port dimensions.

Bore (mm) Stroke (mm) Swept volume (cm3)


Benjamin Super Streak - 30, 120, 82.0

BSA "XL" (Lightning / S'Sport?) - 29, 70, 46

Cometa 300 - 26, 80, 42.5

Cometa 220 - 26, 82, 43.5

Cometa Fenix 400 - 26, 100, 53.1

Crosman Quest - 25, 100, 49

CZ Slavia 634 - 25, 77, 37.8

Diana 25 - 25, 55, 27

Diana 31 and 34 - 28, 80, 49.3

Diana 46 - 28, 85, 52.3

Diana 48 / 52 - 28, 100, 61.6

Diana 54 - 28, 105, 64.4

Diana 350 - 28, 115, 70.8

Diana 460 - 28, 114, 70.2

Gamo 610 - 25 , 85 , 41.7

Gamo Delta Fox - 25 , 61 , 29.9

Gamo Shadow 640 - 25 , 90 , 44.2

Gamo CFX, 440, 890, 220, Whisper, Shadow 1000, Viper, Elite, CF20 and CF30 - 25 , 100 , 49

Gamo 1250 - 29 , 118 , 77.9


Hatsan 70 - 27 , 100 , 57.3

Hatsan 105 - 27 , 100 , 57.3

Hatsan 55S Magnum - 27 , 103 , 59

Hatsan 60S - 27 , 100 , 57.3

Hatsan 80 - 27 , 98 , 56.1

Hatsan 125 - 29 , 120 , 79.5

Hatsan 135 - 30 , 120 , 87

Industry AR1000 - 26 , 107 , 56.8

IZH 22 - 25 , 62 , 30.4

IZH 38C - 25 , 51 , 25

IZH 53M - 25 , 40 , 19.6

IZH 60 - 25 , 57 , 28.0

IZH61 - 25 , 57 , 28.0

IZH MP 512 - 25 , 82 , 40.3

IZH MP513 - 28 , 120 , 73.9

Norica Dragon, Storm, Marvic Gold - 26 , 100 , 53.1

Perfect a 50 - 25 , 75 , 36.8

Remington Genesis 1000 - 29 , 82 , 54.2

Webley Patriot - 30 , 114 , 80.5

Weihrauch HW57 - 26, 81. 3mm x (18mm?) TP - courtesy of Robs 5230

Weihrauch HW98 - (as per HW95) - 26 , 85 , 45

Weihrauch HW90 Gas Ram - 30 , 106 , 75.

Guessing also that the differences in stroke lengths shown for the Hatsan 55, 60 and 80 will be down to measuring inaccuracies and that they share the same strokes?

[harvey_s]

Not sure what use SCR is on it's own?
Surely piston weight and acceleration are major factors along with rifle mass

[TonyL]

Not sure what use SCR is on it's own?
Surely piston weight and acceleration are major factors along with rifle mass

I agree and there are so many inter-related factors contributing to the efficiency and firing cycle of the springer. As we all know it's all a question of balance. However, the SCR can be a useful indicator in terms of efficiency. For example, the HW77 has a high SCR and is regarded as an efficient power plant. The B2, with its high TP volume as standard, benefits from a raising of the SCR via reducing the transfer port diameter, as Mick (T20) found.

[Brian Haigh]

[QUOTE=brucegill;6226870]Many thanks Mick! Great to have your modded 35 in there too

Finally worked out how to add tables in HTML so will do the sums for SCR ASAP.

Have amended the threads title so we can include AA, LGV etc.... If we can get this going it'll be a cracking point of reference.

If anyone thinks of another column, let me know now as its a PITA to add later [/QUOTE

[T 20]

Hi Brian

SCR is the Static Compression Ratio of a springer action, this is the swept volume of the cylinder divided by the volume of the transfer port, normally expressed as XXX/1.



All the best Mick

[Shed tuner]

Weihrauch HW90 Gas Ram - 30 , 106 , 75.

that's the fac version, UK stroke is ~80mm

[TonyL]

Cheers JB.

[TonyL]

The HW50 piston weighs 186 gm, the HW55 163 gm. The HW55 piston head is aluminium, and extends back into the piston, giving available length for the compressed mainspring of 95.6mm in the 55, against 108mm in the 50.

I suspect that if Venom used the HW50 piston in their 55, it was as much for the extra spring room as the mass.

It appears that the HW99 piston is 156mm long and not 146mm as I'd expected, after further reading it turns out that ONLY the external dimensions of the HW99 action are the same as an Old School HW50 action.

When Weihrauch changed from the Old School 50 to the HW99 they increased the cylinder bore from 25mm to 26mm, they increased the piston stroke from 65mm to 71mm, but more importantly to my search for a suitable piston Weihrauch shortened the transfer port from 26mm to 16mm --- a full 10mm.
This explains why the HW99 piston is a full 10mm longer than I expected as the internal length of the cylinder is 10mm longer than the Old HW50.

All the best Mick

Some excellent information applicable to the "old school" HW50, newer type HW50/99 and HW55 from another thread of Mick's.

[Shed tuner]

measured my HW90 port at 3.0mm x 11mm
(it's now 3.2, which is conservative, but gasrams have more preload)

[robs5230]

Has anyone listed the specs for the HW99S? Or have I just missed it?

Does anyone know whether any changes have been made between the early and later (new) 99's?
Thanks Rob

[T 20]

Has anyone listed the specs for the HW99S? Or have I just missed it?

Does anyone know whether any changes have been made between the early and later (new) 99's?
Thanks Rob

You missed it Rob --- it's in the first post.

-----------bore-stroke-cc----TP--------TP volume---scr--------piston weight

HW99s ---26----71---37.7--3x17?------0.120-----314:1------235 - 225 - 225g piston with seal and no
liner. Add 10g if you leave the weight inside
the piston


I'm pretty sure that the transfer port would be nearer to 16mm in length --- My findings are a couple of posts up.





All the best Mick

[TonyL]

As per Mick's findings:-

"Old school" HW50, later variant (but NOT the HW50/99) with the synthetic seal:-

Bore 25mm, Stroke 65mm. Transfer port 3mm X 25mm. Piston weight 200 - 202 grams.

Thanks, Mick.