Scope mount question

bernie · September 2, 2013, 09:12 PM

This is as much a math question as a smithing question. I have a chance at an Enfield Sporter (No.4 Mk I) but it has a problem. It has a piece of angle iron screwed into the side of the receiver so that it comes over and there is a flat edge at the top of the receiver. To this is screwed a Weaver base and a VX-II scope is mounted to it.

This is the problem, with the scope adjusted all the way up, with no more adjustment, it still shoots about 2.5 feet low at 100 yards. How much of an angle would need to be milled into the weaver base to get the scope up some? The mount is about 4.5" long. How much metal would have to be machined off of one end?

Thanks.

g.willikers · September 3, 2013, 08:57 AM

Is this mount home made?
Kind of sounds like it's angled or bent way too much.
2.5 feet at 100 yds?
That's gonna' be hard to correct.
Silly question, but the reticle is being adjusted downward in the scope, yes?

Roughedge · September 3, 2013, 03:47 PM

I only do it if I have to but you can take a piece of brass shim stock and bend it to the shape of the scope and put it under the scope in the front mount and it will bring it up, make take two pieces and be sure not to tighten and crush the body of the scope.

Wyosmith · September 3, 2013, 04:19 PM

Well to bring it back to the rough center of the scope’s adjustments you'd need to move the point of impact not just 2.5 feet, but about 6.5 feet. That way you get your scope somewhere in the middle of its range of adjustment.
In a 4.5" length I'd start with about .080"
To test this place and .080" shim under the rear side of the base and fire a few shots. If that makes it hit about 6’ higher you have your answer.
So then you's shim the base in a mill .080" and taper it the way it should be, and bolt it all back together.
Then zero in the rifle as you would any other.

bernie · September 3, 2013, 08:02 PM

Thanks for the input, all of this info is the reason that I asked!

Scorch · September 4, 2013, 02:43 AM

Roughly 30 minutes of angle. Break out your old trig book. Turns out you will need to remove .050" tapered from one end a 6" mount.

Clark · September 4, 2013, 08:09 AM

2.5 feet / [100y =300 feet] = Shim / 4.5 inches
minimum Shim = 2.5/300 4.5 inches = 0.0375 inches
But what you want is the rifle on the paper when the reticle is in the center of the scope tube. The range of adjustment for low power magnification Leupold VX-2 scopes is large [125 moa for 1x4x], the range for high power VX-2 scopes in low [67 moa for 6x12].
If you were at the range with a Leupold VX-2 when you were 2.5 feet low and the end of adjustment...
So if you were 30 moa off with the first scope, you need 92 moa shim.
If you were 30 moa off with the second scope, you need 63 moa shim.
So the optimum shim for the first scope would be 4.5" [sin 92 moa]= 4.5" sin 92/60 degrees = 0.120" shim
The optimum for the second scope would be 4.5" sin 63/60 = .083" shim.
--------------------------------
About 13 years ago there was an early gun forum with a pic posted of an Enfield scope mount made from an L bracket.
I tried to copy that.

Gunplummer · September 4, 2013, 08:57 AM

What kind of scope is it? I have run into early imports that had reverse turret markings. If you moved left with the scale, the strike of the bullet went right. Same with the elevation turret (UP/Down). I seem to remember they were Japanese imports, but am not sure.

bernie · September 4, 2013, 07:32 PM

Clark, that top photo looks almost exactly like it.

Gunplummer, it is a Leupold, so I doubt that the markings are reversed, not saying it couldn't happen, just that I doubt it.

Gunplummer · September 5, 2013, 09:50 AM

Yeah, I doubt it too. I am sure the scopes I am talking about were imports.

September 2, 2013, 09:12 PM	#1
bernie Senior Member Join Date: September 12, 2000 Posts: 145	Scope mount question This is as much a math question as a smithing question. I have a chance at an Enfield Sporter (No.4 Mk I) but it has a problem. It has a piece of angle iron screwed into the side of the receiver so that it comes over and there is a flat edge at the top of the receiver. To this is screwed a Weaver base and a VX-II scope is mounted to it. This is the problem, with the scope adjusted all the way up, with no more adjustment, it still shoots about 2.5 feet low at 100 yards. How much of an angle would need to be milled into the weaver base to get the scope up some? The mount is about 4.5" long. How much metal would have to be machined off of one end? Thanks.

September 3, 2013, 08:57 AM	#2
g.willikers Senior Member Join Date: September 28, 2008 Posts: 10,442	Is this mount home made? Kind of sounds like it's angled or bent way too much. 2.5 feet at 100 yds? That's gonna' be hard to correct. Silly question, but the reticle is being adjusted downward in the scope, yes? __________________ Walt Kelly, alias Pogo, sez: “Don't take life so serious, son, it ain't nohow permanent.”

September 3, 2013, 03:47 PM	#3
Roughedge Senior Member Join Date: January 24, 2011 Location: Monroe,NC Posts: 669	I only do it if I have to but you can take a piece of brass shim stock and bend it to the shape of the scope and put it under the scope in the front mount and it will bring it up, make take two pieces and be sure not to tighten and crush the body of the scope. __________________ The man that die's with the most stuff win's!

September 4, 2013, 02:43 AM	#6
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	Roughly 30 minutes of angle. Break out your old trig book. Turns out you will need to remove .050" tapered from one end a 6" mount. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

September 3, 2013, 04:19 PM	#4
Wyosmith Senior Member Join Date: December 29, 2010 Location: Shoshoni Wyoming Posts: 2,713	Well to bring it back to the rough center of the scope’s adjustments you'd need to move the point of impact not just 2.5 feet, but about 6.5 feet. That way you get your scope somewhere in the middle of its range of adjustment. In a 4.5" length I'd start with about .080" To test this place and .080" shim under the rear side of the base and fire a few shots. If that makes it hit about 6’ higher you have your answer. So then you's shim the base in a mill .080" and taper it the way it should be, and bolt it all back together. Then zero in the rifle as you would any other.

September 3, 2013, 08:02 PM	#5
bernie Senior Member Join Date: September 12, 2000 Posts: 145	Thanks for the input, all of this info is the reason that I asked!

September 4, 2013, 08:57 AM	#8
Gunplummer Senior Member Join Date: March 11, 2010 Location: South East Pa. Posts: 3,364	What kind of scope is it? I have run into early imports that had reverse turret markings. If you moved left with the scale, the strike of the bullet went right. Same with the elevation turret (UP/Down). I seem to remember they were Japanese imports, but am not sure.

September 4, 2013, 07:32 PM	#9
bernie Senior Member Join Date: September 12, 2000 Posts: 145	Clark, that top photo looks almost exactly like it. Gunplummer, it is a Leupold, so I doubt that the markings are reversed, not saying it couldn't happen, just that I doubt it.

September 5, 2013, 09:50 AM	#10
Gunplummer Senior Member Join Date: March 11, 2010 Location: South East Pa. Posts: 3,364	Yeah, I doubt it too. I am sure the scopes I am talking about were imports.