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Bulldog44

M38 Hollow Core Scope Project 2016 - Bulldog44

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I would be very interested in buying one of these once you are up and running, I already have an original set of front and rear lenses, so I can install them. :)

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Not much I can say that hasn't already been said except I WANT ONE or maybe two...

 

that's no moon, Kim Kardashian is bending over again...

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Quick Update-

 

Custom fitting a lens in the objective lens assembly piece will require some resin removal and a few good ideas on how to approach this. Casting the entire part with the lens still inside resulted in a thick opaque lens to clear away. To make things easier I test casted the same part with simple solution. I inserted a piece of PVC tubing into the mold about the same in diameter as a the tubing directly standing on where the lens is. Once the resin cured I was able to remove the tube and there was no opaque resin lens to drill out. Its not a perfect method but it reduces a little but of work to get a lens mounted.

 

M38%20Scope%20Parts%202016%20Objective%2

 

 

   My next goal is to design a new insert tube that displaces a slightly larger area directly behind the outer ring. This will make it even easier to accommodate a lens. More research!! ^_^

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Hi Brian,

 

This is coming along really nicely, I was wondering do you know the size/ thread of the screws needed for the two holes on the base?

 

Cheers Bryn

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Brian, take care - you are getting deeper and deeper into that rabbit hole :lol:

 

Awesome work. This puts future scope modifications into a new dimension...

 

Will see if I can submit measurements of the prisms from the monoculars later.

Edited by T-Jay
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20964174711_2daf1abffd_b.jpg

 

Here is a picture that was made for a different thread. I checked the prisms and the dimensions are:

20.2 mm on the two equal sides, 28.0 - 28.4 mm on the long side and 11.5 mm wide/thick.

These are big and don't cause any magnification. To get this, there needs to be the correct distance to the functional lenses...

 

On the other side: we would not want it to work correctly, because the scopes on the movie prop were mounted backwards. Meaning, if you look through them, you see things smaller.

Maybe we find a way to modify the lens-setup to really get some magnification, although looking into the wrong end. Time will tell...

 

Any physics teachers around? :D

Edited by T-Jay
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Actually on the e-11 the scope is mounted looking forwards.  And works up to 4000 yards!

 

I love this project.

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Actually on the e-11 the scope is mounted looking forwards. And works up to 4000 yards!

 

I love this project.

Absolutely...

They were mounted with the small lens forward and a gap between the viewers eye and the rear lenses, if you try to put your eye right up to the lens you get a blur...

Think the distance from your eye needs to be about 6 inches, or there about...

 

the force? oh I'll use the force, bring me a hammer...

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I put my face up to the rear of the e-11 and move forward and back until the distance is correct, and then the field of view opens up.

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I've noticed people often make the mistake of thinking the scopes are on backwards due to the fact you view standard telescopes and binoculars through the smaller lenses, it's not till you actually look through one yourself that you see how they work properly...

 

the force? oh I'll use the force, bring me a hammer...

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The M145 the US Army currently uses is the same way. 185142971cb55d5dec016872d11af875.jpg

The little end is the objective lens. I smoked so many soldiers as they walked on to my range with it on backwards!

 

 

Jim M.

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That is some very interesting information. I always thought the scopes in the movies were mounted incorrect. (edited my text above)

 

Well, in that case we might have a chance to get a resin scope working somehow...  someday... :)

Edited by T-Jay

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I priced up a UK manufacturer for the prisms, ball park figure £300 a pair...

Still working on it...

 

the force? oh I'll use the force, bring me a hammer...

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Yikes! Could almost by a real one for that price!

 

 

Jim M.

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Yikes! Could almost by a real one for that price!

 

 

Jim M.

It's better than the $1400 count chocula was quoted lol...

 

the force? oh I'll use the force, bring me a hammer...

Edited by AWOL

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Anyone have a CO2 laser cutting device lying around in the garage? :laugh1:

 

In all seriousness, I think a cast version of the original prism in a suitably-clear resin would probably work, too.

 

Some of the higher-end clear casting polymers have a refractive index very similar to that of glass (1.5) and thus should substitute perfectly. Not trying to push this on anyone though as this is not my build and I don't have a pressure casting pot or a real M38...

 

Maybe Kev can find a cheap glass prism alternative in the UK.  :icon_beg:

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Would these work? Only $4.20 each. They have them in a variety of sizes. The 12mm hypotenuse would seem to match the dimensions Brian posted.

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Would these work? Only $4.20 each. They have them in a variety of sizes. The 12mm hypotenuse would seem to match the dimensions Brian posted.

Dimensions are different but cheap enough for someone to try...

 

the force? oh I'll use the force, bring me a hammer...

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Hi Brian,

 

This is coming along really nicely, I was wondering do you know the size/ thread of the screws needed for the two holes on the base?

 

Cheers Bryn

Sorry so late replying to this thread. I will check the base screw size. Not sure how accurate of a size i can make but I will post that once I get home.
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20964174711_2daf1abffd_b.jpg

 

Here is a picture that was made for a different thread. I checked the prisms and the dimensions are:

20.2 mm on the two equal sides, 28.0 - 28.4 mm on the long side and 11.5 mm wide/thick.

These are big and don't cause any magnification. To get this, there needs to be the correct distance to the functional lenses...

 

On the other side: we would not want it to work correctly, because the scopes on the movie prop were mounted backwards. Meaning, if you look through them, you see things smaller.

Maybe we find a way to modify the lens-setup to really get some magnification, although looking into the wrong end. Time will tell...

 

Any physics teachers around? :D

Thanks Tino for your kind words. I am still debating if I should make the larger lens assembly piece a solid cast or a hollowed center cast. The hollowed one is tricky to make but makes installing the lens easier. I tried this with the smaller one but had mixed results. I need a new method.

Thanks for posting the prisms from your kit. Too big but its good to know if they might have fit or not. Still I think there is some way to use them in the scope but not using the prism cell I casted. Just a a modified prism cell should work.

Cheers!

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Actually on the e-11 the scope is mounted looking forwards. And works up to 4000 yards!

 

I love this project.

 

Thanks Vern. I am glad you like the project.

 

I've noticed people often make the mistake of thinking the scopes are on backwards due to the fact you view standard telescopes and binoculars through the smaller lenses, it's not till you actually look through one yourself that you see how they work properly...

the force? oh I'll use the force, bring me a hammer...

The M145 the US Army currently uses is the same way. 185142971cb55d5dec016872d11af875.jpg

The little end is the objective lens. I smoked so many soldiers as they walked on to my range with it on backwards!

Jim M.

I had read in a few older posts about how these scopes were actually used and how you need to look through them. Thank you all for clarifying that. I will need to re-edit my parts label sheet as I have the larger lens marked as the objective lens. That should be the ocular lens according to what you all posted. Let me know if I am getting this all wrong.

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Anyone have a CO2 laser cutting device lying around in the garage? :laugh1:

 

In all seriousness, I think a cast version of the original prism in a suitably-clear resin would probably work, too.

 

Some of the higher-end clear casting polymers have a refractive index very similar to that of glass (1.5) and thus should substitute perfectly. Not trying to push this on anyone though as this is not my build and I don't have a pressure casting pot or a real M38...

 

Maybe Kev can find a cheap glass prism alternative in the UK. :icon_beg:

 

Thanks for looking into this. Lost of different options to look at for this.

Outstanding work! Can't wait to see more (and then buy one from you) ;)

thanks. Glad you like the scope. Hope to work out some pricing and packaging details very soon. It takes a bit of time to cast each scope so I don't have a lot ready yet. Quality is also an issue as I had casted a few with one or two tiny air bubble holes in noticeable areas. I literally have to sit the and spin the mold by hand for 15 minutes to ensure the bubbles are kept at bay. Trying to make some device to just spin them for me but time , money and space are a problem at the moment.

 

Dimensions are different but cheap enough for someone to try...

the force? oh I'll use the force, bring me a hammer...

Yes, cheap indeed compared to some sites I found. Looks like a good option.

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Would these work? Only $4.20 each. They have them in a variety of sizes. The 12mm hypotenuse would seem to match the dimensions Brian posted.

Those look very much like the prisms almost identical. If I get some extra cash I will try to buy some and see if they would fit. Thanks for finding these. Very cool to see something for a reasonable price.

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Sorry so late replying to this thread. I will check the base screw size. Not sure how accurate of a size i can make but I will post that once I get home.

 

All good mate, did some digging around and found a thread where Aaron (useatt2) posted a link to a source for some screws that fit :)..

 

http://www.mcmaster.com/#92220a171/=yi0cyr

 

Cheers

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