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Looking for the actual dimensions to locate the pads (repro) onto a No4 body.
Seems to be a plethora of copies of the drawings for the bracket components AND the pads themselves.
Is thee or was there EVER a standardized drawing shewing the correct location if the various holes in the left side of the body?
Or was it one of those "bespoke" situations?
I don't know if a standardised drawing exists Bruce, but I've never seen one if it does. Peter has mentioned in the past that a relaxation was approved allowing the front pad to be set back a little so that the rear thumb screw hole cleared the hardened locking recess area with measure of safety, which suggests that there had been at least an agreed process for pad fitting. I've built up a few 'faux' 4T's & rebuilt an awful lot of Bubba'ed real ones, as well as the other rifles that I've come across over the years, & I have never seen this relaxation in practice on a genuine 4T. If I were to hazard a guess, I would suggest the start point is the front edge of the front pad sitting snugly against the vertical ledge formed by the body sidewall & the receiver ring, the minor step on the side wall being kissed with a miller to ensure a flat surface that is in line with the bore.
It would be interesting to see if anyone has something more concrete.
This rifle turned up at a local show maybe a decade ago as a typical "basement" sporter.
The date and the lack of a serial number might suggest it was a factory reject, but there were probably pads and bits laying around at Long Branch as there were at H&H for a long time after production ceased, and this might be just someone fiddling around on a quiet day.
The holes etc. long predate the appearance of reproduction pads on the market and notice the four holes for a Weaver (IIRC) mount that was slapped on at one point; those were also a thing of the past well before repro pads came along.
So, maybe a discard from the early Long Branch conversion program, or maybe not! The set-back of the pads is interesting as it fits with the issues of drilling through the hardened body side. (superficial hardening of the small recoil lug??)
Note the broken off tap; the threads are 0 and 4BA incidentally.
As for the drawing question, there must have been one, and its probably to be found with all those RSAF(E) drawings of alternate mounting systmes kindly posted by Simon(?) some time ago.
The bottom line of course is that the exact location of the pads is determined by the bracket being fitted.
If the mating surfaces of the pads are correctly machined in relation to the bracket "bore" , and the flat for the front pad is machined square to the rifle's sighting planes (for want of a better term), then the front pad (if square itself) will also be square to the sighting planes. Then all that remains to be determined is the position of the rear pad vertically which determines declination (assuming there is none built-in to the bracket) and in the horizontal plane which determines lateral "windage" alignment.
Since there is never a machined flat for the rear pad on the body side, and since we know the body sides were not a control surface, presumably the jigging was accurate enough that after the pads were fitted, the rifle was set up in the jigs and the mating surfaces on the pads were machined, as there was always enough variation possible in the depth of cut on the rear pads to make up for any variation in the thickness of the body sides?
Otherwise it would have been necessary to set up the front pad, attach the bracket, and adjust the rear pad vertically and horizontally until the bracket and bore were collimated. Except of course that there is no provision for lateral movement in the front pad, if the mating surfaces between pad and bracket are to be in full contact.
Almost as laborious to describe as it is to do.... :D
Interesting piece. The positioning of the pads would have been very much further rearward than what I think was in mind at the time. Note the witness lines where someone has scribed around a set of pads..........the rear one would be so far back it would barely clear the safety lever (in the 'off' position).
Butting the front pad up against the breech ring makes a lot of sense. When the rifle recoils, the shoulder of the breech ring will transfer the impulse directly to the front pad, not just via some dinky screws. As the mount is a rather substantial chunk of steel, it will help "link" the rigid front pad to the slightly more precarious rear pad.
The issue of precise "collimation" still exists, unless someone makes an "image-moving' clone of the appropriate scope.
All of this has come to the surface since, as "lock-dawn therapy" I have bee considering turning my totally "bitzer" No4 Mk ll into a faux 4(T) so I can use the same rifle and ammo in different matches, and when the appropriate season rolls around, take it for a walk in the weeds looking for a nice hat-rack.
Honestly, I think the Griffin and Howe rigs as seen in Canada look more robust, but info on them seem even less available.
The G&H type mounts are all very well if one has the windage-adjustable rear ring on the mount. Otherwise collimation is a pain. Won't matter so much for shorter ranges of course if just zeroed at 200 and then used at 1-300 etc.
But yes, they are more robust than the typical pads which Peter informed us tended to shoot loose or even fracture the spigot on the front one.
The Italian repros of the "C67" type G&H base were very good, but still lots of sharp edges sticking up when the scope is removed, just waiting to get bumped and make it impossible to get the mount onto the rail. Alright if the scope is left on, or a cover of some kind is fitted to the rail to protect the dovetails.
And of course you need the G&H upper mount, which isn't cheap unless you get lucky at a show etc., which does happen as I got this for $25 one year - he named the price not me!
Bruce the Field No4 mount is good ( only 1" rings), the Fultons no drill mount is also good. A piece of angle with a rail fixed to it works just as well and can be made to look like an original at a glance.
Double info.
Could the issue of getting proper alignment between the scope mount fittings and the bore be helped; by using a laser bore sighter in the chamber and a laser pointer rigged into the scope mount.
That would allow you to sight the laser's on your workshop wall initially to get close. Then at a longer distance before final soldering of the pads.
That is exactly what I did for the IWS brackets I had made.Quote:
Originally Posted by 30Three
Attachment 114459
The Mount and pads drawing does provide the location dimensions of the pad centre line.
Front face of action to centre of front pad is 1.5inches, then front pad to rear pad centre line is then 3.6inches.
These identical dimensions appear on 4 different and revised mount drawings, from 1940 to 1970.
A post-war drawing apparently.
Interesting that the collimation tolerance is 5 MOA! :eek:
Anyone know what "C.P.C. Treatment 600" is?
Quote:
Originally Posted by Surpmil
C.P.C is a UK manufacturer of chemicals, protective coatings paints and oils (WD40 type stuff)
No idea what their '600' product may have been but their product range would fit into the notation :
"Phosphate finish 1/1 Finished with Black (spirit) stain and C.P.C. Treatment 600"
The No32 bracket drawing was the 1970 version, amended 7 times from original.
Attachment 114504
Also the wartime trials no53 mount drawing dated 1944 has the same pad placement.