The Webley Mercury pistol saga continued. Part 2.

[ccdjg]

John--How do the dimensions of the pistol cylinder and barrel compare to a Milbro Cougar?

Hi Guy, I had a quick look at the Cougar and the cylinder OD is almost the same as mine so I would guess that the inside diameter is going to be pretty similar, at 25mm. Looking at the piston travel (very approx.) this gives a swept volume of about 34 cc. My Mercury has a swept volume of 27 cc, so it is about 20% lower.
The Mercury barrel is 170mm long, the Cougar is 200mm (real barrel, not the fake outer).
So I am not expecting mine to be as powerful as the Cougar, but then again I will be able to use a stronger spring because of the double cocking stroke. It will be interesting to see how much power I can squeeze out of it.

[Geezer]

This is great. Wish I had 1% of those skills.

[Shed tuner]

awesome work...

[Garvin]

I've added inks in the gallery to John's previous projects. It's a very impressive body of handiwork so far!



Lincoln Jeffries patent pistol
Haenel Sport Modell 55R
Frank Clarke twist grip
Webley Whiting
Hill patent pistol

[ccdjg]

Thanks for putting those pics and links up, Danny, and for sorting the pictures out. There are another two guns somewhere, and this Mercury will be the eighth I've made when it is finished.
I think I'll hang my hacksaw up when I get to 10.

[Garvin]

Thank for putting those pics and links up, Danny, but I can't take credit for the guns shown in pics 4 & 5 as they were made by other hobbyists (the twist -grip was made by Mac Evans and the Webley Whiting by Leonard Joe). The correct pics of my efforts are in the links though.

Mac had a slightly different take on the visual appearance of the twist-grip than I had, and his gun predates mine by several years. Len's Webley Whiting looks virtually identical to mine but is constructionally superior in certain respects.

Corrected.

[ccdjg]

It has been more than a month since I last posted, so in case some of you who have been following this thread are wondering what has been happening, here is a quick update.

Everything was going well until it came to milling a slot in the barrel for the front sight. I took meticulous care in appropriately clamping the barrel/barel housing unit in the lathe (difficult due to its awkward profile) and ensuring that the slot would be perfectly aligned with the barrel sight line. I was also very careful to ensure that the slot did not go too deep and penetrate the bore. Unfortunately I was so preoccupied with these details that I didn't spot the elephant in the room. The milling was proceeding slowly and smoothly and I was starting to congratulate myself on a tricky step completed, when I realised that I was milling the slot on the underside of the barrel. I won't bore you with the details of what went through my head, or what I said at the time, but it wasn't "Oh dear me!"

I tried to salvage the barrel housing/detent unit, but I had fixed the barrel in too well and couldn't remove the barrel without damaging the housing drastically. So I had to bite the bullet and make a complete barrel/ barrel housing/ detent all over again. Not something I relished.

I have also had to make a new piston from scratch, as I found that the precision steel tubing I had used was just that little bit too slack in the cylinder. Normally this is not a bad thing in a springer as you only need the piston seal to be a close fit, but in this design you need maximum contact between the cocking link and the piston notch to take the cocking force. Any excessive play and the cocking link can ride out of the slot. I found that with a powerful spring in the cylinder there was a tendency for slippage and deformation of the piston slot.

As I could not buy any steel tubing with a closer fit to my cylinder, or any with an adequate wall thickness that would let me turn it down to the right diameter, I had to make the piston the hard way, by turning down solid bar to the right diameter and then boring it out. Anyway, this has now been done and the new piston works fine, with no signs of slippage. The cocking link has been heat hardened, and the piston itself case hardened, so there should now be little wear with frequent use.

So the gun is more or less finished, and all that remains to do is some checkering to the grips, the lettering to be etched, and the whole thing blued. When it is completely finished and its performance assessed I will put together a final account in Part 3. I must admit, I am getting to like the dual cocking action more than I thought I would.

[ccdjg]

Well, I decided the piston was a bit too heavy and was probably keeping the power down, so I decided to get rid of some of the weight by milling slots in the sides. The piston does unfortunately have to have quite thick walls (about 3mm) compared to most other pistons, because the cocking and sear notches are milled into the wall. The thick wall more than doubles the weight compared to the pistons of similar sized pistols. My piston actually weighed in at about 185 grams, which can be compared to the mere 70 grams of the pre-War slant grip Webley Mark 1. After milling four suitably spaced slots I was able to bring the weight down to about 120 grams, and sure enough the power went up. To try and get even more weight off, I then cut a wide groove around the circumference of the piston head. This brought the weight down to 108 grams, and as that was good enough for me, I then case-hardened the piston. This process left the piston black and scaly so I did a bit of a clean up, and then suddenly the whole thing fell into two halves in my hands. I had not allowed for the conical depression inside the piston head when I cut the groove into the head. I had left only a wall of about half a millimetre thickness holding the head to the body. The case-hardening process had then made the wall brittle and probably introduced some stress fractures as well, so the whole thing was just hanging together by a thread. Needless to say I was pretty mad, and at that particular moment I was sorely tempted to throw the whole project in the bin and call it a day.


In the following picture, (A) shows the first piston I made that proved to be too slack. (B) shows the new, perfectly functional, piston before I had cut the groove around the piston head. (C) shows the piston after grooving and case hardening, and giving up the ghost.


After 24 hours things didn’t look so black, so I ordered some more 30mm bar and then set about making a third piston. Onwards and upwards, as they say! So I have now made another piston, and learning from my mistakes I have reduced it in weight to 118 grams without weakening it. Picture (D) shows the new third piston after case-hardening and cleaning. I have changed the PTFE seal for a leather one, which I think performs better. The new piston works really well in the pistol.





I am only thankful that the second piston fractured when it did, and not when the gun was loaded and at full cock. I could have put a pellet through the TV or even worse!


Although everything structural is finished, I still have to apply the lettering, black the gun and then do some accuracy/chrono testing. I will report on this in Part 3, barring any more accidents.