Enfield No. 4 MkI* Repro Sniper Project - Scope Mounting Issues

Let me start by disclosing - I'm new to the forum and my gunsmithing experience is limited. That said, and despite the many caveats I've read, I've decided to take a sporterized Long Branch No. 4 Mk1* I picked up and create a repro "(T)" sniper. I've thoroughly read the excellent posts by Peter Laidler. I purchased a set of pads, screws, and mount from Acuumount, and a No. 32 MKII repro scope from Numrich. Per Peter's instructions, I have collimated the scope using the very handy rig he described (which I built on my 3D printer. I have installed the front pad, per his instructions, with the pad located as far down and forward as it would fit.
My issue is the placement of the rear pad. When I temporarily place the rear pad in what appears to be it's correct position (lower edge resting on the beveled edge of the receiver sidewall), the point of aim is WAY high. Using a laser bore sighter I measured that the pad needs to be mounted about 0.13" higher in order to bring the point of aim about 2" above the bore sight. This works out to about 130 MOA based on the 3.6" distance between the two mount attachment screws. I confirmed this measurement with POA being about 12" above the bore sight at a wall 326" from the optic. All of this is with the tip of the reticle optically centered to the scope tube. I put a Weaver K4 in the mount and got the same results, so I don't think it's the scope. I've checked the critical dimensions on both pads and the mount vs. the military spec and they are in pretty close agreement, so I don't think the problem is there. I'm going to take this to the range and check my calculations at 25 and 50 yards, but I suspect this will confirm my findings (assuming I can even get POA and POI on the same target at those distances).
Has anyone encountered this issue? I can mount the pad higher but that will put the 1/4" screw very close to the top edge of the receiver sidewall.
The windage is actually pretty good as is, and I can taper the front pad a bit to fix that.
Thanks in advance for any advice.
JD

Assuming the pads are duplicates of the originals you should probably start by having the area where the front pad sits machined to match the back of the pad. That will lower the front pad considerably.

Originally the mating surfaces where the bracket sits on the pads were machined after the pads were fitted to the rifle. That was done using jigs to hold the barrelled action in the proper alignment using the bore as the control surface.

Still, a bit of work with dial indicators, drill rod ground to be a push fit in the bore and a long enough milling machine table should do it. The trick is, how do you collimate the bracket to the bore? A No.22 scope in the bracket and boresight the barrel on a wall chart 20+ feet away? Something like that.

Could be done on a substantial CNC router too for that matter.

Bottom line either the front goes down or back goes up, but the flat on the front pad which bears against the inside face of the bracket must be parallel to the bore in the horizontal (windage) plane. Once that is done the rear pad can be slipped under the bracket and it slid down onto the rear sidewall of the receiver/body, hopefully lining up properly but perhaps requiring either lapping down to the right thickness or the addition of some brass shims underneath....

The Accumount front pad are about 0,6 mm too high
Maesured in the center of the spigot.
I have installed 4 sets of this mounts.
In all cases i have to made new front pads.
This measurements is confirmed by comparing
To a original front pads.

Jsne

I converted my Long Branch No.4 and found the Accumount pads to be rubbish. Do they have square corners, if so then i would give them the elbow.

I don't know who makes them but try and source pads with rounded corners, i brought mine from DS Solutions in the UK for around £70. These were alot better although the rear pad still required a very thin shim. If fitted correctly you can blend it into the pad and make it invisible.

I'm guessing you haven't drilled the back holes yet, but i recommend buying brand new cobalt drills for this. The action is case hardened on the inside and breaking through is a challenge not like the 3 front 4BA holes which are soft as butter in comparison. Oh and nice fresh taps, especially the 1/4 BSF as your hit the hard spot like a wall. Go very slow and lots of tapping lube.

The pads that Fultons sell are the best that I know of, & physically also resemble original pads very closely. I have used them before now to restore original T's that had been mucked about with. I've no experience of the pads that John sells at DS Solutions, but I know him & he is a decent bloke, so I would expect them to be ok.

Since we are talking repro equipment here could one not just lap the bracket down in the front?

Or hell, stick a shim under the rear of the scope?

You said you have a 3D printer?
Make your self some scope shims!

The plastic 3D printed shims will compress over time, reproduction or not i say no reason not to do a proper job.

Your only regret it later down the line when your POI is shifting...

Brownells sells scope shims for under $20.

I fully understand doing it right, I bought a No.22 scope for collimating for that very reason. But, if you don’t have access to jigs, long millling machines, properly ground drill rods or equipment to make your own pads, the average hobbiest wants it to look the part and work.
Shimming will work.


Not purposely trying to be obtuse, just giving suggestions.
Unless he’s making these to sell to people, why not weigh all options?

I totally understand your point, all you really need tho is a mill and a few tools. Just need to be creative with clamping to work around making jigs.

You can just shim the rear pad with thin sheet metal bent to shape to match the angle. Small bit of draw filing on the edges and a reblue and the join will vanish.

You need to do a proper job!
The no.32 scope have stops in both end of the
Adjustments trawel.
So the zero must be correct the first time

Jsne

Quote:

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Originally Posted by jsne

You need to do a proper job!
The no.32 scope have stops in both end of the
Adjustments trawel.
So the zero must be correct the first time

Jsne

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Yes very true, but as long as the scope is colimated to the bore axis how you achieve this is of no consequence.

Quote:

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Originally Posted by jsne

You need to do a proper job!
The no.32 scope have stops in both end of the
Adjustments travel.
So the zero [collimation] must be correct the first time

Jsne

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I know you know JSNE! ;)

Quote:

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Originally Posted by jonh172

Yes very true, but as long as the scope is colimated to the bore axis how you achieve this is of no consequence.

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Not true.
As our new friend already mentioned in post 1
The 1/4” threat will bee dangerous close to the edge
Of the rear receiver wall
So close that the high spots of the tap will break through
The surfase.
Only one thing to do.
Get an other front pad or make a new one.

Jsne

---------- Post added at 08:32 PM ---------- Previous post was at 08:25 PM ----------

Quote:

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Originally Posted by Surpmil

I know you know JSNE! ;)

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Hi Surpmil
Thank you for correct my post 👍

Jsne

Attachment 105993Attachment 105994I have been installing scopes as per the OPS experience. A centered scope tube puts the pointer tip in the location of theoretical best optical clarity, with equal elevation adjustment as depression (or there about). However we use the scopes at ranges of 100 - 200 - 300 - 400 yards - where we really need the theoretical best optical clarity and we don't need any adjustment depression below a 100 yard zero. So a centered scope can be 15+ MOA high (the OPS example sounds higher tho). As long as the windage comes into centerline at all ranges (colimated) when all the screws and pads are tightened up, the 15 MOA over gets taken up by zeroing for POI (adjusting down), leaving plenty of elevation adjustment and the best optical clarity at useful ranges. I have also observed that the rear pad groove location varies from any one manufacturer of pads - I end up using the highest of the pads that sit on the action wall and place the screws mid meat around the rear locking lug and have a collection of "lower groove pads" forming. I just set up a 1941 Longbranch along these lines, next up is 1944 BSA.