15 vs 20 moa base

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CSully

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Hello All,

I'm new to precision rifle shooting and I'm at the point I want to upgrade my base.

I'm currently shooting a Savage 10TR 308 with a Bushnell Elite Tactical LRS 6x24x50 FFP scope.

My question is regarding the base. I have an opportunity next month to shoot at Borden at 1000 yards. I know my 0 MOA base won't get me there. The majority of my shooting will be between 100-300 yards, but on occasion I'll need to reach 1000. My concern is with a 20 MOA base I'll be bottoming out my scope at the shorter ranges....so I'm considering a 15 MOA rail, but will that be sufficient to get me to 1000 when needed? Am I putting myself at a happy medium? I don't know the math yet to figure out how to calculate the range of the glass based on the rail.

Any insight would be appreciated. Thanks in advance,

~Sully
 
Depending on your trajectory (velocity & ballistic efficiency of the bullet you're using), your .308 will need somewhere around 30 MOA to reach 1000. Others who more commonly shoot .308 can comment more accurately once you give up your ballistics details.

Assuming your scope has minimum 50 MOA range of elevation adjustment (don't know, really but starting here), from center of range, you'll have 25 MOA up travel. If 100 yard zero happens to land in the center of the adjustment range, you'd need another 5-ish MOA to get to 1000.

So, a 15 MOA rail should be fine in this case. If your scope has more internal adjustment capability, you may not even require a canted rail. It's been my experience that a 20 MOA rail will not often impede your ability to zero at 100 yards for most set ups.

Rooster
 
I run a 20 MOA rail on both my bolt .308s and have had no issue zeroing at 100 yards. On my current match gun with a 26" barrel pushing 175 RDFs @ 2760 fps at say 60F and a DA of 1500ft, I need 9.32 mil, which works out to 32.04 moa to get to 1000. For my backup gun with a factory 20" barrel pushing 178s @ 2541 fps in the same environmentals, I need 11.21 mil or 38.54 moa. For my M14S, with a 0 moa ARMS 18, pushing 168s @ 2620 fps, I needed to max out the elevation at 29 moa and hold over 0.6 mil for a total of 31 moa to make hits at 830 yards. All this to say that there really is no reason not to get a 20 moa rail, who knows, you might get the opportunity to push out a bit past 1000 one day.
 
Besides a rail, how about a set of rings that will let you shim your scope as needed?

Burris rings with inserts... there are a couple of options.

I use both base and rings and let's me fine tune my zero to suit whatever shooting I plan on doing. Also, let's me center my windage which really helps in improving both optics and tracking as you go through the full range of scope adjustment.

Another option.

Jerry
 
Keep in mind that the more you crank the turret down for your 100 yard zero, the more you compress the erector tube springs.

Over time, the springs can take a set and not have enough pressure when you crank up for a long shot and fire the rifle... Then you are into a warranty repair for the scope.

When you have a tilted base, you might choose to store the rifle with a 600 yard zero or some setting that leaves pressure off the erector tube springs.

So there is a certain trade off that you should keep in mind.
 
My question is regarding the base. I have an opportunity next month to shoot at Borden at 1000 yards.
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I do believe the 1000 yard range (Mons range) at CFB Borden is still closed. At least until next year. You may be referring to Amiens range, it's 500 yards. Your model (Bushnell Elite Tactical LRS 6x24x50 FFP) has approximately 68 moa (or 19 mils, as per Bushnell website) of total vertical adjustment. A 15 moa rail would work fine for 1000 yards. If you have a zero mounted rail on already, according to my arithmetic you won't need canted rail in Borden at Amiens range next month. If this is the precision-sniper event on the 15th, hope to see you there.
 
Mystic Precision said:
Besides a rail, how about a set of rings that will let you shim your scope as needed?

Burris rings with inserts... there are a couple of options.

I use both base and rings and let's me fine tune my zero to suit whatever shooting I plan on doing. Also, let's me center my windage which really helps in improving both optics and tracking as you go through the full range of scope adjustment.

Another option.

Jerry
Click to expand...

I used a set of the Burris XTR Signature rings on my Savage 10TR to mount my Sightron glass and used the 0 MOA base that came with the rifle and then used the inserts to get 25 MOA cant slope on the scope. It works great. I have shot out to 800 meters with the rig and still have some adjustment left.
 
Terry Perkins said:
I do believe the 1000 yard range (Mons range) at CFB Borden is still closed. At least until next year. You may be referring to Amiens range, it's 500 yards. Your model (Bushnell Elite Tactical LRS 6x24x50 FFP) has approximately 68 moa (or 19 mils, as per Bushnell website) of total vertical adjustment. A 15 moa rail would work fine for 1000 yards. If you have a zero mounted rail on already, according to my arithmetic you won't need canted rail in Borden at Amiens range next month. If this is the precision-sniper event on the 15th, hope to see you there.
Click to expand...

No I'm going as a guest at the end of the month. You should see me at those events next year though, I'm doing my intro day shoot on the 14th at the Winona Range.

Cheers,

~Sully
 
BadAsMo said:
Keep in mind that the more you crank the turret down for your 100 yard zero, the more you compress the erector tube springs.

Over time, the springs can take a set and not have enough pressure when you crank up for a long shot and fire the rifle... Then you are into a warranty repair for the scope.

When you have a tilted base, you might choose to store the rifle with a 600 yard zero or some setting that leaves pressure off the erector tube springs.

So there is a certain trade off that you should keep in mind.
Click to expand...

Or you can just use a quality scope and not worry about this.
 
kc34 said:
I used a set of the Burris XTR Signature rings on my Savage 10TR to mount my Sightron glass and used the 0 MOA base that came with the rifle and then used the inserts to get 25 MOA cant slope on the scope. It works great. I have shot out to 800 meters with the rig and still have some adjustment left.
Click to expand...

Glad the rings worked well for you. They offer so many options in scope set up

Jerry
 
kthomas said:
Or you can just use a quality scope and not worry about this.
Click to expand...

Like what Leupold Mark 4, Schmitt Bender, March or Nightforce?

Check with any of the guys who were at the World F-class championship in Ottawa a couple weeks ago and you will learn that each of these premium scope brands failed during the match.

There are certain models that employ a coil spring instead of a leaf spring for the erector tube. That seems to be the key feature to address the point, but you need to watch for it when selecting a scope. IOR has it and I think US Optics and others like this premium Vortex, but it's no guarantee it cannot fail.

Spring life is a byproduct of the compression ratio and time. The less you hold a spring in a compressed state the longer it will last. Its also relative to what percentage of the spring free length it is being compressed to. Since the space between the erector tube and outer tube is finite, the brand has no influence over the reality of this space constraint.

A larger tube diameter (Like Burris XTR II 34 mm) and or coil spring are the logical solutions because it provides the spring with more space for compression and is therefore compressed a lower percentage of its free length and the spring lives longer. (Engineering 101 stuff.)

See the little bump at a 45 degree angle below the parallax turret... that's a coil spring tube but this is their top of the line scope and it is unaffordable for most.

vtx_rfl_rzr-amg_6-24x50_mrad_bl_1__1.jpg
 
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You will be good to go with the 20 moa rail and that scope. You will still have adjustment left over in both directions (-l00 to +1000).

I have a Bushnell Elite Tactical 3-15x40 mounted on a 20 moa rail. This scope only gives me 42 moa total elevation adjustment. I can hit my 100 yard zero 4.5 moa from bottoming out which leaves me with 37.5 moa of up adjustment before I bottom out again. I'm pushing the limits with this scope but it still gets me from 100 to 1000. When the rifle is stored I just back the turret off 1 full turn from my 100 yard zero. Don't know if it's necessary or not but it makes me feel better anyways.

Your 6-24x50 with a 30mm tube has (if I recall correctly) somewhere in the high 60's for elevation adjustment. The 0moa rail will not quite get you to 1000 but the 20 moa rail will let you stretch farther than you will ever need with adjustment still left over at both ends.

A 30 moa rail should even work with your scope but you will be close to bottoming out at 100 just like I am with my set up.

The 20moa rail should be just what you need.

EDIT: Of course this is still subjective to your particular bullet weight/velocity combination but the numbers should still be in the ballpark.
 
BadAsMo said:
Like what Leupold Mark 4, Schmitt Bender, March or Nightforce?

Check with any of the guys who were at the World F-class championship in Ottawa a couple weeks ago and you will learn that each of these premium scope brands failed during the match.

There are certain models that employ a coil spring instead of a leaf spring for the erector tube. That seems to be the key feature to address the point, but you need to watch for it when selecting a scope. IOR has it and I think US Optics and others like this premium Vortex, but it's no guarantee it cannot fail.

Spring life is a byproduct of the compression ratio and time. The less you hold a spring in a compressed state the longer it will last. Its also relative to what percentage of the spring free length it is being compressed to. Since the space between the erector tube and outer tube is finite, the brand has no influence over the reality of this space constraint.

A larger tube diameter (Like Burris XTR II 34 mm) and or coil spring are the logical solutions because it provides the spring with more space for compression and is therefore compressed a lower percentage of its free length and the spring lives longer. (Engineering 101 stuff.)

See the little bump at a 45 degree angle below the parallax turret... that's a coil spring tube but this is their top of the line scope and it is unaffordable for most.

vtx_rfl_rzr-amg_6-24x50_mrad_bl_1__1.jpg
Click to expand...

Myself and thousands of others have never had these issues. The evidence provided of the f-class world's is purely anecdotal, and a very small sample size as to be considered statistically irrelevant.

Failures happen in any brand of scopes, for a number of different reasons. Rarely do they happen on high end scopes (IOR is not by any means a high end scope brand btw), and if they do, the companies will take care of you.

Keeping a 600 yard zero on a scope for fear of a statistically improbable issue is just silly. Have fun sailing targets on your first rounds at a comp or on range day.
 
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kthomas said:
Myself and thousands of others have never had these issues. The evidence provided of the f-class world's is purely anecdotal, and a very small sample size as to be considered statistically irrelevant.
Failures happen in any brand of scopes, for a number of different reasons. Rarely do they happen on high end scopes (IOR is not by any means a high end scope brand btw), and if they do, the companies will take care of you.
Keeping a 600 yard zero on a scope for fear of a statistically improbable issue is just silly. Have fun sailing targets on your first rounds at a comp or on range day.
Click to expand...

Wow...

Anecdotal... irrelevant...

?????

Yourself and thousands of others have never had these issues.... hmmm... I suppose its the same thousands of others who buy gear but rarely shoot at long range.

I was at a match last September that had one stage that took out 4 such scopes out of only 15 shooters in one squad alone. That is not irrelevant.

IOR is not a premium brand??? at north of $3000 each what the heck is premium?

The World F Class Championship is a select group of the best shooters in the world who shoot thousands of rounds per year at long range and use the very premium scopes you have in mind as superior where several failed at this one match.

There are few better test bases anyone could dream up, yet you call it irrelevant...

Sure some scopes are better than others but you have yet to mention one specific model that is bullet proof reliable....

Lay it on us dude... enlighten us kthomas. What scope is so reliable that a warranty is simply not required?
 
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BadAsMo said:
Wow...

Anecdotal... irrelevant...

?????

Yourself and thousands of others have never had these issues.... hmmm... I suppose its the same thousands of others who buy gear but rarely shoot at long range.

I was at a match last September that had one stage that took out 4 such scopes out of 15 shooters in one squad alone. That is not irrelevant.

IOR is not a premium brand??? at north of $3000 each what the heck is premium?

The World F Class Championship a select group of the best shooters in the world who shoot thousands of rounds per year at long range and use the very premium scopes you have in mind as superior that several failed at this one match.

There are few better test bases anyone could dream up, yet you call it irrelevant...

Sure some scopes are better than others but you have yet to mention one specific model that is bullet proof reliable....

Lay it on us dude... enlighten us kthomas. What scope is so reliable that a warranty is simply not required?
Click to expand...

Posts like this remind me why I left CGN. Too many keyboard commandos on here to readily deliver bad advice. The more I train, shoot and compete, the more that I've come to realize that most people on the internet (and especially CGN) are full of ####.

No wonder CGN is turning into a graveyard in the precision rifle world.

Best of luck.
 
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