Ruger MK-II scope rail hole dimensions

milktree

milktree

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I have a 22/45 and a Mk-II, neither of which are drilled/tapped for a scope rail.

Does anyone have the actual specs for the screw thread size and hole spacing?

I have a rail I want to mount, so I can measure the hole spacing, but... there's something hinky about the middle hole.

The distance between the first and third holes is 2.500", which confirms what I've found elsewhere on the net. But the distance between the first and second holes is... not easy to measure because it doesn't line up on anything even. Somewhat more than 1-27/32" (1.844"), but not really 1-55/64" (1.859") If I use my calipers and measure the outside and inside distance and average I get 1.851", but if I try to line up the points of the caliper I get 1.841" One place on the 'net says it's 1.855" So, a spread of nearly 0.02" (which is a lot)

Given the close fit between the screws and screw holes in the rail, I really want to get this right, and not "close enough" I have access to a milling machine, so I can get pretty damn close to 0.001" precision.

On page 40 of the manual downloaded from Ruger's website it says, "Drilling and tapping instructions are available on request." So I requested drilling and tapping instructions, but got an invitation to mail both guns to Ruger so they could do it for me, for the low low price of $95 including shipping, each. (which includes the rail, so I guess it's not that bad)

But I want to this myself. I don't want to ship them to a smith.
 
jeeze, do you have machining experience? if not, I see this going south fast. just sayin', not criticizing. :)

keep northeast arms in peabody in mind in case you change your mind about having outside help.
 
greencobra said:
jeeze, do you have machining experience? if not, I see this going south fast. just sayin', not criticizing. :)
Click to expand...

Heh.. I have a milling machine, on which I have some experience. And I have a guy (the guy who gave me the mill) who has quite a lot of machining experience, so I'm reasonably confident I won't screw it up too badly.

And... they're just MK-IIs, they're nice, but not "brand new Model 41" nice. If I screw it up, the worst that happens is I have a cosmetically flawed pistol that still doesn't have a scope rail!
 
My friend had a MKII tapped in the early 90's that he bought at Roach's in Cambridge. He called Ruger and they sent him the base and instructions. I am sure they have that electronically available these days. Do you intend to use a Ruger rail? Give 'em a ring, worst they can say is they can't help.

Customer Service

Have you thought about the no drill mounts available?

Good luck.
 
one-eyed Jack said:
I used a B Square mount in my MK2. Works good and you can see the irons under it. Jack.
Click to expand...

I have a nice B Square on my older Redhawk but have seen some nice Rugers with Weigand's no drill mounts. Lots of brands and makes.

Ruger 22/45 scope mount MKI MKII MKIII MKIV Weaver WEIG-A-TINNY<sup>®</sup>

Scope Mount Ruger MKI MKII MKIII MKIV 22/45
No Drill and Tap

If you have an older Ruger MKI, MKII, MKIII, MKIV, 22/45 that's not drilled and tapped you can install this WEIG-A-TINNY® Scopemount without making any permanent alterations to your favorite pistol. Remove the rear sight, insert the threaded dovetail filler and install the mount with the screws provided. Accepts all Weaver style rings and accessories and most Picatinny rings and accessories.
5-1/4" long, silver or Black, matte anodized finish, weighs 2.5 ounces, comes with mounting hardware and screws.
 
SERE said:
My friend had a MKII tapped in the early 90's that he bought at Roach's in Cambridge. He called Ruger and they sent him the base and instructions. I am sure they have that electronically available these days. Do you intend to use a Ruger rail? Give 'em a ring, worst they can say is they can't help.

Customer Service
Click to expand...
https://www.ruger.com/dataProcess/customerService/

I haven't called them, but I filled out the form on their web page. "we'll do it for you for $90" was their answer. (not really helpful)

Have you thought about the no drill mounts available?
Click to expand...

Yea, but... I dunno, they seem like kind of a hack. And I don't want to lose the iron sights (or have to re-mount and re-adjust them if I want to swap back)
 
The correct way is with a mill. Some of the threaded holes need to be a specific depth otherwise you will drill into the chamber. Before you mill it get a Ruger factory scope base just to verify that you have the correct locations. I feel that the Ruger base is the best because it is light, sturdy and high Quality. IMG_0842.JPG IMG_0841.JPG
 
SERE said:
He called Ruger and they sent him the base and instructions. I am sure they have that electronically available these days
Click to expand...

milktree said:
I haven't called them, but I filled out the form on their web page. "we'll do it for you for $90" was their answer. (not really helpful)
Click to expand...

That may be best/easiest for someone that lives in an apartment and doesn't have their own mill. However, it is not what you asked for.

[B][COLOR=#00b300]S&WMan[/COLOR][/B] said:
The correct way is with a mill. Some of the threaded holes need to be a specific depth otherwise you will drill into the chamber. Before you mill it get a Ruger factory scope base just to verify that you have the correct locations. I feel that the Ruger base is the best because it is light, sturdy and high Quality. View attachment 249124View attachment 249123
Click to expand...

Ta-Da! nice post, S&Wman.
 
S&WMan said:
The correct way is with a mill. Some of the threaded holes need to be a specific depth otherwise you will drill into the chamber. Before you mill it get a Ruger factory scope base just to verify that you have the correct locations. I feel that the Ruger base is the best because it is light, sturdy and high Quality. View attachment 249124View attachment 249123
Click to expand...

Sweet! Thanks! That's exactly what I was looking for!
 
S&WMan said:
The correct way is with a mill. Some of the threaded holes need to be a specific depth otherwise you will drill into the chamber. Before you mill it get a Ruger factory scope base just to verify that you have the correct locations. I feel that the Ruger base is the best because it is light, sturdy and high Quality. View attachment 249124View attachment 249123
Click to expand...

I don't suppose you have any idea what "note 1" refers to, do you? (the little triangles with the "1" in them)

It seems like all the information is there.
 
milktree said:
I don't suppose you have any idea what "note 1" refers to, do you? (the little triangles with the "1" in them)

It seems like all the information is there.
Click to expand...
Sorry I don't have that info. This was all that Ruger sent me years ago. I never did go forward with having my Mark II drilled and tapped.
 
I do know that the factory rail is placed just forward of the factory sight. The factory rail has a trough milled down the center so you can use the sight with the rail mounted. The mounting screw locations shown on the instructions are almost moot if you have the factory sight and a factory rail. I would at least locate the first screw hole using the scope rail as a template.
 
S&WMan said:
I do know that the factory rail is placed just forward of the factory sight. The factory rail has a trough milled down the center so you can use the sight with the rail mounted. The mounting screw locations shown on the instructions are almost moot if you have the factory sight and a factory rail. I would at least locate the first screw hole using the scope rail as a template.
Click to expand...

The thing I want to be sure of is the relative spacing of the holes. "don't hit the factory sight" I can probably just fake, it probably doesn't matter much so long as all three go into the frame and the rail doesn't touch the sight.

But man... getting the spacing of that middle screw wrong would bum me out.
 
mac1911 said:
Why not just place the rail where you want it mark the holes and go at it.
Click to expand...

"mark the holes" is the tricky bit. The mounting screws are a pretty close fit in the rail, so if the holes are off by "a little bit" the rail might not mount.

I'm going to just make a "close enough" guess for the rear hole, such that the rail has sufficient clearance from the rear sight, but I'm going to be super precise between the rear and middle, and rear and front holes.
 
one-eyed Jack said:
Thanks. Didn't know that. I bought mine 30 yrs ago. Jack.
Click to expand...

You can still find them on eBay.

But really I'd rather have a scope mount attached in a more repeatable way. Anything that relies on friction or clamps to non-repeatable surfaces doesn't inspire confidence in me. I recognize that's probably an unwarranted fear.
 
I had a bsquare mount and it would move when firing mini-mags. Not a lot, but after 50-70 rounds it would travel enough to block the ejection port, so I went with mounting the rail.
 
chrbla2000 said:
I had a bsquare mount and it would move when firing mini-mags. Not a lot, but after 50-70 rounds it would travel enough to block the ejection port, so I went with mounting the rail.
Click to expand...

Holy crap, that must have been hell on its accuracy!
 
milktree said:
"mark the holes" is the tricky bit. The mounting screws are a pretty close fit in the rail, so if the holes are off by "a little bit" the rail might not mount.

I'm going to just make a "close enough" guess for the rear hole, such that the rail has sufficient clearance from the rear sight, but I'm going to be super precise between the rear and middle, and rear and front holes.
Click to expand...
Ok risk of sounding stupid or a a**h***
Why not clamp the rail on and put the assembly in the mill. Use a bit thats the same size as the holes and just kiss it to make a center mark?
Im just thinking how i would do it here at home with my hold drill press and limitted tools and skills.
 
mac1911 said:
Ok risk of sounding stupid or a a**h***
Why not clamp the rail on and put the assembly in the mill. Use a bit thats the same size as the holes and just kiss it to make a center mark?
Im just thinking how i would do it here at home with my hold drill press and limitted tools and skills.
Click to expand...
Speaking as someone with more/better tools, but similar skill, I think that sounds like a good idea.

The only things I can think of are:
1) clamping a couple things with round profiles such that they don’t sit crooked might be tricky
2) if the rail I have is not quite in-spec I’d be transferring wrong dimensions to the receiver. It’d work with *this* rail, but perhaps not one that is in spec. I don’t know how much of a problem this is in the real world.
3) if the drill bit doesn’t fit exactly or the receiver is clamped down in not quite the right place either the rail will be damaged or the holes will be in the wrong place.
 
milktree said:
Holy crap, that must have been hell on its accuracy!
Click to expand...

I'm not sure I explained it fully, it wouldn't noticeably move per shot, just sort of creep slowly and after 50 or so rounds creep just enough to get in the way of the ejection port. It could be totally my fault, I don't like cranking things down so tight that it might cause damage, so it could be that I didn't tighten the mount enough. Tell you what, if you have interest in the bsquare mount, PM me and let me know, I'll ship it to you. The one I have looks like this:

306732.jpg


-chris
 
milktree said:
Speaking as someone with more/better tools, but similar skill, I think that sounds like a good idea.

The only things I can think of are:
1) clamping a couple things with round profiles such that they don’t sit crooked might be tricky
2) if the rail I have is not quite in-spec I’d be transferring wrong dimensions to the receiver. It’d work with *this* rail, but perhaps not one that is in spec. I don’t know how much of a problem this is in the real world.
3) if the drill bit doesn’t fit exactly or the receiver is clamped down in not quite the right place either the rail will be damaged or the holes will be in the wrong place.
Click to expand...
I don't know , think your over thinking it. Buy a factory pistol with factory rails and holes or send it in to ruger...
 

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