Making new breech seal for Webley Service (and others)

[Phil Russell]

I have had need to fit a new breech seal to my Webley Service MKII. I did look at getting one from a 'spares' shop but was put off by price and the oft used term 'may need fitting'. Thus I may well have ended up resizing the bought option, so a seach for an alternative was called for. The old breech seal on my MkII is fitted on a removable brass carrier and was about 2mm thick. I thought that a new one could be made from pliable plastic and opted to firstly use a 2mm chopping/cutting board discarded from the kitchen but on reflection a lid off an old food container that was about 1.75mm thick may have been better.
The outer diameter of the seal is 0.5", the inner diameter that fits over the peg on the brass carrier is approx 7mm but I found 1/4" to be excellent for providing a good push fit on the carrier that stayed put. Cutting the seal thus required hole punches (wad punches) of 0.5 and 0.25". Using these to cut holes is no problem; the skill comes in getting the inner hole exactly lined up so that it is perfectly central to the outer diameter. Believe me when I say that this is very difficult to do freehand.
So a simple jig was made comprising a 0.5" diameter body about 6mm deep (to fit inside the 0.5" cutter) that had a central peg 0.25" diameter and 2mm high in the centre of one end. A few minutes on the mini-lathe with 15mm delrin rod and it was made. Now I accept that not everyone will have a lathe but it would be quite possible to make this jig using a pillar drill or other fixed power drill and files / emery paper. It could be made from wood or other material.
In use, a 0.25" hole is punched in the seal material and the jig fitted on top; the 0.5" cutter is then placed on top of the jig body and clouted. The result will be a perfect 0.25" hole in the centre of a 0.5" disc. Obviously different jigs could be made to suite different measurements for other seals for other rifles
The new 2mm seal was a good push fit on the brass carrier. When fitted to the rifle the barrel closed and provided a quite firm closure of the retaining rotary lever. I felt this was maybe a tad too tight so the seal and carrier was removed and the thickness slightly reduced using emery paper. It took very little effort to get a good closure and had me thinking that maybe if I had fitted the 1.75mm thick plastic the closure would have been good first time.
Will it last? I do not know but suspect it will. It has shown no inclination to move when fitted so I am hopeful. A chrono check showed perfectly acceptable performance.
Cheers, Phil

IMPORTANT: from the posts that follow it is clear that the thickness and maybe other dimensions of these seals can vary. Please adjust any fabrication to suit your seal.