Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Rifles, Bullets, Barrels & Ballistics

Rifles, Bullets, Barrels & Ballistics Applied Ballistics


Reply

Shimming rear base

 
LinkBack Thread Tools Display Modes
  #1  
Old 06-18-2002, 10:41 PM
Silver Member
 
Join Date: Mar 2002
Location: Prince George British Columbia
Posts: 128
Shimming rear base

A buddy of mine cant get his '06' to zero at 1000yds so any idea how much shim it would take under the rear base to get him into the ball park.
Reply With Quote
  #2  
Old 06-18-2002, 11:16 PM
Platinum Member
 
Join Date: May 2001
Location: Pennsylvania
Posts: 1,757
Re: Shimming rear base

.025" to .030" tapor or rear height shims
__________________
Darryl Cassel
Reply With Quote
  #3  
Old 06-19-2002, 12:15 AM
Platinum Member
 
Join Date: Jun 2001
Location: Palmer, Alaska
Posts: 2,539
Re: Shimming rear base

I think it's something like .010" is worth "about" 5 moa? I'm not sure though. I had to shim my Ruger base .020" on the 416Wby before I bought the Burris rings and .040" inserts.
__________________
Brent Moffitt
Reply With Quote
  #4  
Old 06-19-2002, 06:19 AM
Platinum Member
 
Join Date: May 2001
Location: Pennsylvania
Posts: 1,757
Re: Shimming rear base

Brent

Each .001" tapor is worth 1 MOA (or 1" rounding it off) at one hundred yards.
Most rifles at Willimsport need around 20" to 24" of elevation at 100 yards to be on target at 1000 yards.
With his 30/06 or a 308 Win, one would need around 30" of lift (depending on the load) at 100 yards. He should start with a .025" or .030" to get on target at 1000 yards and be able to utilize his scope center setting and for further shots if he would want to.
Darryl Cassel
__________________
Darryl Cassel
Reply With Quote
  #5  
Old 06-19-2002, 10:49 AM
Silver Member
 
Join Date: May 2001
Posts: 256
Re: Shimming rear base

One thing to keep in mind is that it's better to shim a one piece base. That way the whole base is at an angle and the rings are still in alignment with eachother. When you have 2 piece bases and shim just the rear, now it is elevated above the front shim and your rings will not be aligned properly. I always lap in my rings but that only accounts for a few thousandths, putting in your shim will throw you off whatever thickness you put under there and it's too much to lap in. Now when you tighten your rings around the scope you are putting uneven tension on the scope body which can lead to trouble. I feel the one piece is the best way to go for shimming.
Having said that, I have indeed shimmed the rear base of a 2 piece system myself and it seemed to work ok. In theory though, it's not a good idea. At least that's my opinion.
Reply With Quote
  #6  
Old 06-19-2002, 04:54 PM
Silver Member
 
Join Date: Jul 2001
Location: San Antonio, Texas
Posts: 244
Re: Shimming rear base

remember guys that the amount of shim needed is directly proportional to the lenght of the base itself. Not all bases are the same length. Lets say your base is 7.05" front to back, now add a shim of .020". This would mean that for every 7.05" the .020" elevation is gained. Since we typicaly use 100yds as a zero and there are 3600" in 100yds, it is easy to figure the true amount of shim needed. (3600/ length of base)x(thickness of the shim) ex. (3600/7.05 = 510.63829) multiply by .020" = 10.212765". So if your base is 7.05" long and you use .020" shim you would get 10.25" elevation. Remember, the shorter the base the less shim you will need. A 6" base would give 12" elevation with .020" shim.
Reply With Quote
  #7  
Old 06-19-2002, 11:05 PM
Platinum Member
 
Join Date: Jun 2001
Location: Palmer, Alaska
Posts: 2,539
Re: Shimming rear base

Txhunter, that's about all I got with a .020" shim. I think I did a little figuring like that back then to get that .020" also. Depending on where the crosshair is situated in the tube (I don't know) and where it is placed relative to the rear base being shimmed would be the exact length to figure it on , true? Or is it the occular to the crosshair distance that is correct?

I agree the two piece base is puttin the tweek on your tube as it did mine. The Leopolt 3.5-10x40 has NO evidence of the misalinement though, it looked and felt new when I took it off to put it in the Burris rings with inserts.

It shocked me too because I had the screws as tight as I could possibly get them. Almost had to drill them out.

The onepiece is the way to go or the Burris set on a two piece.
__________________
Brent Moffitt
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Shimming rear base
Thread Thread Starter Forum Replies Last Post
Leupold 2-Piece Standard Scope Base Savage 10/110 Round Rear TORCHRIDER Optics For Sale 1 04-11-2011 01:58 PM
Shimming the rear mount. Nodak7mm Long Range Scopes and Other Optics 3 01-13-2007 10:06 PM
Scope shimming? Casey Napier General Discussion 7 12-01-2006 01:18 PM
base shimming? CIG The Basics, Starting Out 9 05-23-2005 11:06 AM
WTB: Kuharskey rear base ewallace Guns For Sale 0 05-29-2002 07:11 AM


All times are GMT -5. The time now is 05:22 AM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC