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How to calculate which scope will fit?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/18/2011 at 15:46
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Optics GrassHopper
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I'm new to the forum, but I've been reading some good info here.
 
I have a T/C Contender with a Kendricks .223Rem rifle barrel.  It's got a Conetrol base and Huntur Low rings.  I'm having a tough time trying to figure out what size scope will properly fit it.  The big problem I'm running into is the Objective, some are just too big.
 
I was told to put a dowel in the rings and measure the height from the barrel to the bottom of the dowel.  The rings are 1"/25.4mm.  The gap from barrel to the base of the dowel is 9.6mm.  If I calculate it correctly ([12.75 (ring) + 4.8 (gap)] x 2 = 35, I have a maximum of 35mm objective diameter I can get in a scope.  Is that right?
 
I've bought Bushnell with a 32mm Objective scope but when I checked my calipers on the OD, it was 40mm and it was too big (it ended up on my 10/22).
 
Any recommendations?  I was hoping for a sub-$200 scope.  I was looking at a Burris Timberline 32mm, Konus Konushot 32mm, Burris Fullfield II 35mm, Vixen 32mm, and a Leupold VX-II 2-7x28mm Ultralight.
 
I'm planning to use it for mostly target shooting, but I may take it to the field for varmint.  There are no iron sights so I can't really shoot it right now.
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/18/2011 at 16:02
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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/18/2011 at 16:17
RifleDude View Drop Down
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Originally posted by FullOfShot FullOfShot wrote:

I'm new to the forum, but I've been reading some good info here.
 
I have a T/C Contender with a Kendricks .223Rem rifle barrel.  It's got a Conetrol base and Huntur Low rings.  I'm having a tough time trying to figure out what size scope will properly fit it.  The big problem I'm running into is the Objective, some are just too big.
 
I was told to put a dowel in the rings and measure the height from the barrel to the bottom of the dowel.  The rings are 1"/25.4mm.  The gap from barrel to the base of the dowel is 9.6mm.  If I calculate it correctly ([12.75 (ring) + 4.8 (gap)] x 2 = 35, I have a maximum of 35mm objective diameter I can get in a scope.  Is that right?
 
I've bought Bushnell with a 32mm Objective scope but when I checked my calipers on the OD, it was 40mm and it was too big (it ended up on my 10/22).
 
Any recommendations?  I was hoping for a sub-$200 scope.  I was looking at a Burris Timberline 32mm, Konus Konushot 32mm, Burris Fullfield II 35mm, Vixen 32mm, and a Leupold VX-II 2-7x28mm Ultralight.
 
I'm planning to use it for mostly target shooting, but I may take it to the field for varmint.  There are no iron sights so I can't really shoot it right now.
 


Keep in mind the objective diameter is the diameter of the objective LENS, not the diameter of the objective BELL.  The objective bell diameter of most scopes I've checked have been 6mm larger than the objective lens diameter (ex:  42mm objective scope = 48mm dia objective bell).  To positively ensure clearance, it might be a good idea to just add 10mm to the objective diameter and factor your clearance based on that.  This assumes a scope without adjustable objective ring.  Since you're concerned only with the difference between objective housing dia and tube dia on one side for barrel clearance, you would use 1/2 the dia difference for your barrel clearance.  The dowel method works fine, but you can also just take your ring height from the top of receiver to bottom of the ring saddle and add the height of the step from barrel to receiver for your total clearance.  Then make sure (obj bell dia)-(main tube dia)/2 is less than that total height measurement and you're good.


Edited by RifleDude - November/18/2011 at 16:29
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/18/2011 at 16:43
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Optics GrassHopper
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This is the only forum that's made it absolutely clear on how to calculate the correct scope sizing!  Thanks!
 
You're right, of course.  I meant Objective Bell Diameter, that was the deal breaker.  I think I might have to buy the Leupold VX-II 2-8x28mm Ultralight scope.  That's the only one that has the correct dimensions.  All the others, after some math, seem too large.  Looks like my budget for a scope has gone up by $100.
 
The Weaver will work, too, but a little more magnification would be nice.
 
Originally posted by RifleDude RifleDude wrote:

Originally posted by FullOfShot FullOfShot wrote:

I'm new to the forum, but I've been reading some good info here.
 
I have a T/C Contender with a Kendricks .223Rem rifle barrel.  It's got a Conetrol base and Huntur Low rings.  I'm having a tough time trying to figure out what size scope will properly fit it.  The big problem I'm running into is the Objective, some are just too big.
 
I was told to put a dowel in the rings and measure the height from the barrel to the bottom of the dowel.  The rings are 1"/25.4mm.  The gap from barrel to the base of the dowel is 9.6mm.  If I calculate it correctly ([12.75 (ring) + 4.8 (gap)] x 2 = 35, I have a maximum of 35mm objective diameter I can get in a scope.  Is that right?
 
I've bought Bushnell with a 32mm Objective scope but when I checked my calipers on the OD, it was 40mm and it was too big (it ended up on my 10/22).
 
Any recommendations?  I was hoping for a sub-$200 scope.  I was looking at a Burris Timberline 32mm, Konus Konushot 32mm, Burris Fullfield II 35mm, Vixen 32mm, and a Leupold VX-II 2-7x28mm Ultralight.
 
I'm planning to use it for mostly target shooting, but I may take it to the field for varmint.  There are no iron sights so I can't really shoot it right now.
 


Keep in mind the objective diameter is the diameter of the objective LENS, not the diameter of the objective BELL.  The objective bell diameter of most scopes I've checked have been 6mm larger than the objective lens diameter (ex:  42mm objective scope = 48mm dia objective bell).  To positively ensure clearance, it might be a good idea to just add 10mm to the objective diameter and factor your clearance based on that.  This assumes a scope without adjustable objective ring.  Since you're concerned only with the difference between objective housing dia and tube dia on one side for barrel clearance, you would use 1/2 the dia difference for your barrel clearance.  The dowel method works fine, but you can also just take your ring height from the top of receiver to bottom of the ring saddle and add the height of the step from barrel to receiver for your total clearance.  Then make sure (obj bell dia)-(main tube dia)/2 is less than that total height measurement and you're good.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/18/2011 at 16:54
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Optics GrassHopper
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I've also notice that any Objective that's 28mm is either a Handgun scope or a Rimfire.  Leupold looks like the only one making a scope that will fit my requirements.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/18/2011 at 23:20
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Well you could change rings that is what most of us would do.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/19/2011 at 07:51
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Optics GrassHopper
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Originally posted by Urimaginaryfrnd Urimaginaryfrnd wrote:

Well you could change rings that is what most of us would do.
 
This! Thanks for stateing the obvious.Excellent
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