I for one would like to see some good pictures of a Webley Screw Grip compared to the for lack of the correct name "Trade Action w/extensinon & spindle actuated 3rd lock" that Wrights & others used for their heavy proof guns.
Here is a picture posted on the WR Leeson site:
More helpfully, there is a very detailed discussion of the Webely Screw Grip posted on that site:
http://wrleeson.co.uk/design.htmHere is the nub of the discussion:
An alternative design to the Greener 'cross bolt' or Westley Richards Dolls Head was the Webley Screw Grip top extension patented by T. W. Webley and T. Brain (P. Webley & Son) under patent No: 3053 in 1882. The design made use of either the more ornate and complex Dolls Head type or a straight or blade type extension. The later dispensed with the Dolls head leaving a simpler straight slot cut in the top edge of the standing breech. Although the blade design would have been less expensive to produce the Dolls head variant seems to have been the preference of W R Leeson.
The design is based on an external screw or thread mounted on the vertical spindle of the top lever inside the standing breech. On the upper part of the spindle, inside the standing breech is also a cam mechanism. When the top lever is operated to open the breech, the screw mechanism rotates inside the spindle assembly and places an upward lifting force on the underside of the top extension. In effect its acts as an assistance to the opening of the breech. When the breech is closed, as the sliding bolts lock into the barrel lumps, the top cam mechanism places a downward force on a stepped lug forming part of top extension. This has the effect of pushing the top extension, whether of the Dolls Head or indeed the Blade Head extension design down into the slot on the upper face of the standing breech. Once home, both the sliding bolts lock into position in the cut outs of the barrel lumps and the third bite mechanism locks home the top extension, ensuring a very strong bolting.
The Webley screw grip satisfies both aspects concerning breech burst and breech/barrel flexing. Barrel flex is overcome when the head itself is located into the slot cut in the standing breech of the action, the barrel being held secure between the fences, as can be seen in the picture above. The second feature is to lock the breech closed in combination with the sliding bolts. This was achieved by a modification to the top lever spindle incorporating a screw thread or cam type mechanism. When the breech was closed the spring mechanism of the top lever ensures the cam exerts downward force on the top extension. The combination of the two design aspects produced an exceptionally strong breech to action joint as well as an aesthetically pleasing feature.
This question was also discussed in some detail here a few years ago:
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=149435&page=1I think to answer the question of whether a gun has the Webley Screw Grip, you need to check not only the barrel extension but also the spindle to confirm it has the camming mechanism.
