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  #1  
Old 03-06-2018, 07:20 AM
Jakeroub Jakeroub is offline
 
Join Date: Dec 2016
Location: Mass
Posts: 394
Default Redfield Jr. 1903a3 Scope Mount Questions

I recently bought a Redfield Jr. S-SPECIAL scope mount base (in red and white box). I was under the impression the the S-SPECIAL bases were the same as (or very similar to) the Redfield Jr. PN 51141, which is the older style bases preferred for 1903a4's. I think I understand that the newer Redfields (PN 47159) won't fit the receiver correctly.

I took a good look at this mount last night, and one thing that didn't seem right is that it came with 6-48 screws. From what I've read, I think the a4's (and vintage commercial mounts) would have had 8-40 screws.

Photo album here: https://imgur.com/a/0zVro

The screws that came with it are 0.137 diameter
The screw hole in he base is 0.164 diameter with a 0.238 c'bore.

It looks like the holes in the base could just fit an 8-40, but I am doubtful that the 0.238 c'bore will take an 8-40 screw head.

I do have access to a mill at work, and could open up the c'bores and holes if needed.

So, my questions are-

What do I have here? Is this "one of the good ones" that will fit the receiver correctly? I tried placing it on the receiver, but I couldn't quite decide if it was sitting right, without tapped holes to use as a reference.

Does this thing just have the wrong screws in the box, and maybe it is meant for 8-40s?

Appreciate any input! Thanks!
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  #2  
Old 03-06-2018, 07:42 AM
Emri Emri is offline
 
Join Date: Feb 2012
Location: Alabama
Posts: 398
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I just measured some Weaver 8-40 scope base screws and the thread diameter was .161"
The head on THIS screw was a nominal .240", but is not for a fillister head hole. (Weaver uses an oval head screw)
Sounds like you have the wrong screws with that base.
The box is certainly old and the base appears to be an "original" one also, not a Chinese copy.

HTH,

Emri
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  #3  
Old 03-06-2018, 07:52 AM
bruce bruce is offline
 
Join Date: Nov 2009
Location: Georgia
Posts: 899
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Obtain some 8-40 screws. Gently see if they fit. If so, all is cool. Check the fit of the base and proceed if it fits. If not, then have to fish around for screws that do fit. That will not be fun. Good luck! Sincerely. bruce.
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  #4  
Old 03-06-2018, 08:03 AM
Jakeroub Jakeroub is offline
 
Join Date: Dec 2016
Location: Mass
Posts: 394
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Thanks for the suggestions. I just ordered a kit from Brownells with long 6-48 and 8-40 screws of various head types, so hopefully one of those 8-40's will fit this mount without requiring modifications.
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  #5  
Old 03-06-2018, 08:50 AM
chuckindenver chuckindenver is offline
 
Join Date: Jan 2012
Posts: 2,527
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screws are 8/40 for this mount..
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  #6  
Old 03-06-2018, 09:45 PM
Randy A Randy A is offline
 
Join Date: Nov 2009
Location: Montana
Posts: 685
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8-40 fit the bore for the screw but some of the screws that you find will have a larger head diameter, you may have to turn the heads down a little bit. I just buy these and cut to length. https://www.brownells.com/gunsmith-t...nt=080-574-006

Even though the 6's head fits in the hole don't use them. BTW that is the newer base, I believe someone stuck it in an old box.
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  #7  
Old 03-06-2018, 09:59 PM
Jakeroub Jakeroub is offline
 
Join Date: Dec 2016
Location: Mass
Posts: 394
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Quote:
Originally Posted by Randy A View Post
8-40 fit the bore for the screw but some of the screws that you find will have a larger head diameter, you may have to turn the heads down a little bit. I just buy these and cut to length. https://www.brownells.com/gunsmith-t...nt=080-574-006

Even though the 6's head fits in the hole don't use them. BTW that is the newer base, I believe someone stuck it in an old box.
Those are the screws I ordered. I have a lathe and can turn down heads if I need to.

Yes, I was afraid this might be a new base in an old box... Would this be one of the bases that arent supposed to sit correctly? If so, I might throw it on a shelf and get something else...
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  #8  
Old 03-07-2018, 08:47 AM
ceresco ceresco is offline
 
Join Date: Oct 2009
Posts: 7,106
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There are small variations in the external receiver dimensions--none of the bases fit perfectly. You can modify the base if needed. Most important is to D&T through the base with it lined up properly on the bore axis. Good Shooting. ..
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