Altering 1" rings to fit a 26mm scope

**Rodrage** · 21-05-2019, 11:04

So as the title suggests, I've got an old German scope, Nickel Marburg, still very clear and bright, BUT 26mm tube.
Seeing I've got a nice old German rifle, M-S 6.5x54, I want to marry the two of them.
Due to some restraints, I'm going to need to ream out, lap out or generally get the fuck out, .6mm of the 1"rings I've got, i.e. 26mm as opposed to 25.4mm. That's only .3mm on the sides.
I do have a lapping kit with 1" bar and I think 240 grit grinding paste. Try and over-lap it? Maybe wrap some sand paper round the lapping bar???

Anybody done this himself or must I talk to a machinist?
What do you DIY guys say?
Thanks,
Rod

**Sean KZN** · 21-05-2019, 17:52

A honing tool correctly aligned will give you good results.

**treeman** · 21-05-2019, 18:07

I have done same thing using a old scope that was broken I glued sand paper to the old scope tube - put a threaded rod through scope with large washer either end. Clamped a board to drill press bed and drilled a hole through plank - use hole in plank to center rod. When scope is turning in drill on rod use hard object to put against one side of scope bell and apply pressure till bell slides on washer centering it better. Tighten washers further - put rings on scope loosely with scope screws hold with fingers. When drill is running move mounts up and down scope using finger pressure to tighten on scope.Oil helps. Tighten ring screws till each half touch - done. Second time round I took both scope rings mounted them against each other on a block and did both same time, worked better.Use engine gasket paper -(velomite ?) soaked in a solvent around scope under rings, it squeegees out when tightening rings and helps forgive the back yard lathe work.
I have done this with my box of scraps and spares to get a scope on a .22 and a .270 - JUST TILL money was in for new stuff, just so I could play.
I do not know what yours is going on and do not propose this as a solution to not buying fitting proper stuff, but it works to get shooting while you wait for proper rings etc.
I have also put half circles of that white water piping in rings that were to big to make use of a old thin tube scope on a pellet gun.

**Rodrage** · 22-05-2019, 12:32

Thanks Treeman and Sean,
I'm first going to look at trying a honing tool as you suggest Sean, it certainly looks the easier way.
Treeman, what size old scope were you using, I don't know where I would be able to find an old 26mm scope to do this. If you use a 1" (25.4mm) one, could I not just try and use the 1" lapping bar that I do have.
Would I need to skim off some metal from the top of the lower ring and the bottom of the top ring also??
I've also used inserts in rings that were too big to fit a 1" scope in 26mm rings so that does seen to work OK.
Let's see what happens!!

**treeman** · 22-05-2019, 18:33

Rodrage - I used a scope because I did not have a rod, in retrospect i could have used a broom handle and just turned it down to one inch.Would have been easier than scope method).
You see I already had that scope modified and used it as a ring lapping tool. Mount rings with scope on rifle tighten up. Remove top rings and color inside of ring engineering blue or Artline marker, put a mild sand paper on old scope and put top rings back not tight. Your mounts are on tight and bottom ring. The bottom set up is aligned by scope when mounting it.Rotate scope a few times and back forth a few times, you will be amazed how little scope to ring contact some rings have(and how skew). Recolor inside rings and do same again, till you see full contact on rings. Clean up job put scope you intend to use on rifle.
Oh - and if you do lap on a rod try mount rings together so that the lapping is true from one ring to another, by the rods being in both same time.
-----Again, this is not gun smithing, just make do for method.

**Andrew Leigh** · 22-05-2019, 20:28

Where are you Rodrage?

**A-R** · 22-05-2019, 21:15

Originally Posted by Rodrage

Thanks Treeman and Sean,
I'm first going to look at trying a honing tool as you suggest Sean, it certainly looks the easier way.
Treeman, what size old scope were you using, I don't know where I would be able to find an old 26mm scope to do this. If you use a 1" (25.4mm) one, could I not just try and use the 1" lapping bar that I do have.
Would I need to skim off some metal from the top of the lower ring and the bottom of the top ring also??
I've also used inserts in rings that were too big to fit a 1" scope in 26mm rings so that does seen to work OK.
Let's see what happens!!

A 1" rod with some thin sand paper glued on should get you close to 26mm. Just polish the ring halves till they fit over the scope tube. If the ring gap is 0,6mm bigger, I don't see any issues besides cosmetics. You can always remove more metal. Polish once, measure twice.

**Rodrage** · 23-05-2019, 11:20

Thanks guys,
A-R, I intend to give it a bash as you've suggested. I've used the lapping tool a couple of times in 30mm and 1" configurations and it certainly works wonders.( it's one of these Wheeler Engineering tools with FAT torque goody etc.- good outfit)
I'm surprised at how quickly the lapping tool and grit removes the metal in the rings, you can definitely overdo it, that's why I'm thinking of just going ahead with it and stop and measure along the way. Sandpaper on it will certainly speed things up, but the grit size is already 240 so it cuts like hell anyway!
As you pointed out Treeman, it is startling how little contact there is before you lap!
Andrew, I'm in KZN near Greytown (little dorp called New Hanover).