Cocking Piece Nose/Sear Adjustment

[tbonesmith]

Hi Gents, a while ago I was doing a trigger job on a No4 or a No1 and I was trying to get the lowest safe trigger pull I could get, and the way I had been doing them to date (freehand on a stone) just wasn't precise enough to adjust the cocking piece sear angle by a degree or other fine margins.
I thought I'd make a stoning fixture but then found I had one in the form of the vice on the mill. By setting up across to 2 identical diameter rods/pins/drill bits you can set the sear angle to a predetermined angle, measured from the underside of the cocking piece to the jaws, or you could add or subtract a degree or 2 or whatever you want from the existing angle.
Once setup I remove the rod closest to the cocking piece and lay a diamond stone across the remaining rod and the sear face and run it back and forth rolling on the rod and stoning the face. If the jaws on your vice are in plane the flat that you stone will be perfectly flat, and square. If you have other grades of stones you just run down them until it's as polished as you like.
This method has given me much more control over these little jobs and cost nothing. It may work well with some of the cheap drill press vices that you can get, and could be no doubt be adapted to many vices or clamp arrangement.
If you tinker a bit it may help you get a better result easier and more reliably.

Information

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[Peter Laidler]

Ah, yes..... needed to think about this before commenting. We used to collect a few of these together, say about 30 or so, and take them to the machine shop where one of the grinder ops would grind the faces to a drawing. On some, it'd go through the case hardness so that meant that they were toast.. The other problem was that you could grind the face, the hardness would remain but the locking lever would not engage the locking lever recess properly in order to enable the locking lever to cam the cocking piece rearwards to draw it out of contact with the sear. So just be aware of this.

Another thing to be aware of is this. If the angle of the nose is too great, in order to lighten the trigger pressure - in that the angle rakes rearwards towards the underside - the following will occur. As the first trigger pressure is taken up, the nose of the sear rides down the sear bent of the cocking piece. If you then release the trigger pressure, the nose of the cocking piece will ride UP the sear bent of the cocking piece under the influence of the sear spring. Are you still with me....., wake up at the back of the class!

If the angle of the sear bent on the front face of the cocking piece is too great, to, lighten the trigger pressures then when the first pressure is taken up and then released, THE SEAR WILL NOT RISE UP THE FACE OF THE COCKING PIECE. This is because the sear spring had insufficient loading to overcome the force of the striker spring holding the nose of the cocking piece keeping the sear nose downwards so that it cannot rise to resume its 'rest' position. This spells danger ahead. So all be warned. I seem to recall that the max sloping rearwards angle permitted is 110 degrees

[CINDERS]

In my paltry experience with these matters I just use a cheap ar$e dremel that stalls in its own shadow with some compound and a small buffing wheel and go over the contacted surfaces on the sear ends and cocking piece nose till they are like a mirror its a slow process as you cannot put any pressure on the wheel lest the motor stall on the small dremel I think the buffing wheel dia is about 10mm thats how small it is.
And whilst the take ups are about the same it appears to one to be lightened as the surfaces slide over each other very well I occasionally give them a coat of silicone spray the rifles are stored in a stable environment so no rust issues and with no alteration to any angles the rifle passes muster when assessed for trigger pull in comps.

The pom's are pretty much tuetoinic in the sense that they do things for a reason and the Lee's are no exception as by trial and error with natural selection what works and doesn't we have the end product that for over a 100 years is still being used in combat or as a 2nd weapon by police forces around the world I surely would not want to be on the receiving end of a MkVII round from a 100 year old rifle.

[Bruce_in_Oz]

This matter has been discussed several times, but bears revisiting.

The VERTICAL angle of the "full bent" (end-face" of the cocking piece is, as per the original drawings, 86 degrees and ten minutes from the HORIZONTAL.

Laterally, it is also DEAD flat (withing bounds of 19thCentury technology), and "dead-square", with "sharp" edges.

That surface was precision surface-ground after the entire piece had been heat-treated.

Importantly, the lower edge of the full bent is to be NO MORE than .020" above the line of the lower surface of the cocking-piece body.

Equally important in this caper is the sear, of course.

The end-face that acts on the cocking-piece is also "dead-square" laterally but radiused along the top and bottom edges.

It is apparent that there were slight changes in overall form of the sear over the years; early ones have several "nice touches" that were skipped over in later production. Interestingly, the critical areas; axis hole, trigger-bearing surface and the "working end" of the sear carried over to the No4 and No5, with both simplifications and extras, like lightening cuts being variously added, but without significantly altering the relationship of those three critical points mentioned above.

[Bruce_in_Oz]

ERRATUM!

Dyslexic Fat Fingers at work!

" ...the lower edge of the full bent is to be NO MORE than .020" above the line of the lower surface of the cocking-piece body."

SHOULD READ:

"......NO MORE than .002" above the line...etc., etc...."

I do NOT have the drawing for the No4 pattern cocking piece, does anyone out there have one lying around for reference?

[30Three]

I made a small rig to surface the cocking piece for my No1 mkIII* that I use in competitions.
Ideally I would like to get one machined out of metal; but the wooden version works quite well as a test piece. Certainly better than trying to do it by hand.
The cocking piece angle can be adjusted by a screw under piece in the lower part of the channel. I use a very fine Arkansas stone and oil and take it slowly.
IIRC the standard rifle is 4° off the right angle and the L39A1 target rifle is 10°.
Attachment 93626Attachment 93627Attachment 93628Attachment 93629

[CINDERS]

FWIW from my perspective I am with PL and BIO that modding the angle on the cocking piece nose can lead to situations not so desirable in the operation of the system as both of them point out the hardening is only X deep go through that and you'll have issues as I would surmise the hardened edge on the sear would quickly gouge out the soft metal pretty quickly on the cocking piece nose.
When we shoot "As issued" the rifle cannot have a lightened trigger the take ups have to be as manufactured also the safety must engage otherwise you get DQ'ed but I guess its up to the person who is using the rifle and how they set it up if it has worked for a 100+ years then that's good enough for me and my polishing of the nose, sear and trigger nodes with what I have will not alter any angles or lose hard facing.

[tbonesmith]

You’re missing the point Cinders. I’m not advocating butchering your rifles, and I’m not saying that stoning the cocking piece is something everyone should go out and do.
It is however and essential requirement sometimes as cocking pieces and be damaged by previous “adjustment” or stoned to unsafe angles. And as a part of setting up a trigger nicely this step can be helpful, especially if you don’t have a large assortment of spares to selectively fit from, or a surface grinder.
Yes it is possible to go through the case hardening, and yes you need to bear in mind all the other related aspects of trigger setup, so well covered in Peters articles.

[CINDERS]

I will agree with you on the spares there are cocking pieces for sale here and in the UK as NOS but they are starting to get up in price now guess they are a finite item.

[Roger Payne]

I've also seen some No4 cocking pieces that are after market investment castings. I don't know enough about metallurgy to know if they may be ok, so if buying spares I always look out for a recognizable factory code. Not seen any after the event examples for SMLE's as yet.