Trying to understand the ramifications of my 35 MOA base....

[libertyman777]

When I first bought my TRG, I picked up a 35 MOA Badger base. I was thinking FFP for Tactical matches, 110 or more MOA of adjustment, etc. But since then, I've realized that some F/TR may be more my speed.

So I'm all hot to buy the Golden Eagle and get started. I call up the guys at Vortex and asking a few questions about the scope. So while I'm on the phone, I asked if he can help me with some rings. I tell him about the Badger 35 MOA base on the TRG. So now I think I have a problem. Or maybe not, I"m not sure.

Anyway, the base exceeds 1/2 the adjustment in the scope by 7.5 moa. It has 55 internally (give or take a few clicks I'm sure) but using those numbers 1/2 of the internal adjustment is 27.5 MOA.

I'm having trouble wrapping my mind around this.

Does this mean that I'll be roughly 7.5 MOA high at 100 yards, which is a 400 yard zero, give or take.

Is this correct?

Or does this mean that I have an almost 925 yard zero with this base?

I realize I'm speaking in broad terms here. I"m using Vortex's LRBC, with a Federal Ammo 175 grain at 2600 fps, 1.75" scope height, 600 ft ASL, local weather,

FWIW, I will be doing most of my F/TR shooting at Talladega, AL which is limited to 600 yards I think. But I would like to be able to make 1000 if needed.

I"m very confused.

 

[dkhunt14]

You will be high. Really hard to tell how much because guns and scopes are different from one to another. A simple solution would be to get another base or use Burris rings with inserts to adjust the MOA. Matt

 

[Depart123]

You can't determine anything until you mount it and try to zero it. You have no way of knowing where your 100 yd zero would fall within the scopes adjustment range, so you have no starting point to go from.

 

[XTR]

Get an EGW 20MOA base for small $$ and you will be fine, put the 35MOA base in the drawer that you will keep all the other stuff that you will collect that you aren't using right now.

 

[Turbulent Turtle]

When I first bought my TRG, I picked up a 35 MOA Badger base. I was thinking FFP for Tactical matches, 110 or more MOA of adjustment, etc. But since then, I've realized that some F/TR may be more my speed.

So I'm all hot to buy the Golden Eagle and get started. I call up the guys at Vortex and asking a few questions about the scope. So while I'm on the phone, I asked if he can help me with some rings. I tell him about the Badger 35 MOA base on the TRG. So now I think I have a problem. Or maybe not, I"m not sure.

Anyway, the base exceeds 1/2 the adjustment in the scope by 7.5 moa. It has 55 internally (give or take a few clicks I'm sure) but using those numbers 1/2 of the internal adjustment is 27.5 MOA.

I'm having trouble wrapping my mind around this.

Does this mean that I'll be roughly 7.5 MOA high at 100 yards, which is a 400 yard zero, give or take.

Is this correct?

Or does this mean that I have an almost 925 yard zero with this base?

I realize I'm speaking in broad terms here. I"m using Vortex's LRBC, with a Federal Ammo 175 grain at 2600 fps, 1.75" scope height, 600 ft ASL, local weather,

FWIW, I will be doing most of my F/TR shooting at Talladega, AL which is limited to 600 yards I think. But I would like to be able to make 1000 if needed.

I"m very confused.

Essentially what your 35MOA mount will do is transform you riflescope setup so the adjustment range will be from 8 to 63 MOA above mechanical 0. Or something like that.

Now, IF (and that's a commercial size if) your setup is perfectly aligned once installed on the rifle, your estimate is pretty close. In reality, the setup could be even worse or not as bad depending on how everything lines up. But even at 600 yards, your scope will be wound down quite a bit, near the end of travel.

So, unless you intend to mostly shoot at 1000 yards, where your scope will be set mostly in the middle of the lens, the very best place to be, I totally agree with the concept of getting a 20MOA base instead.

 

[johnnyi]

So, unless you intend to mostly shoot at 1000 yards, where your scope will be set mostly in the middle of the lens, the very best place to be, I totally agree with the concept of getting a 20MOA base instead.

Our most challenging distance we are shooting the scope the farthest from optical center. Perhaps this will be the ticket?

 

[libertyman777]

Ok, well at least I now understand what’s going on. The base is staying. I’ll just work with it via the Burris inserts if I go with the Golden Eagle.

Thanks for the help!

 

[Turbulent Turtle]

Our most challenging distance we are shooting the scope the farthest from optical center. Perhaps this will be the ticket?

Yeah, essentially it would be better to be as close as possible to the middle (sweet spot) of the lens. It also is better for the springs holding the inner tube to not be compressed so much all the time.

That said, at 35MOA, you kiss the 100 yard zero goodbye and the 300 yard is near the full compression but the other way.

In my March-X scope, I have 60MOA of elevation and I start with a 20MOA ramp. So that gives me 10 down and 50 up. I need about 30 from a 100 yards to get to 1000. That leaves about 17 up or not full compression on the springs.

Now, understanding that the ONLY lens on which the inner tube will move from optical 0 is the objective lens, 13 (33-20) MOA on that lens is about .02 inch from center. I'm using 5.6 inches as the distance from the objective to the inner tube. If we change to millimeters, the focal length used is 144mm and the displacement at 13MOA is about .6mm.

Boy, I sure hope I have the calculations correct, trigonometry can be a bear.

 

[Turbulent Turtle]

Ok, well at least I now understand what’s going on. The base is staying. I’ll just work with it via the Burris inserts if I go with the Golden Eagle.

Thanks for the help!

What will be critical with the Burris Signature rings, which I love BTW, is the distance between the middle of the rings, front and back. That will dictate the cant that you get using the inserts. Burris has a nice grid that lists is all out for you.

 

[libertyman777]

What will be critical with the Burris Signature rings, which I love BTW, is the distance between the middle of the rings, front and back. That will dictate the cant that you get using the inserts. Burris has a nice grid that lists is all out for you.

Ah, I didn’t know that. If I can take out somewhere between 5 an 10 MOA out of the cant I should be able to get somewhere near 12 MOA of adjustment up to 1000 and down to 600.

Yeah, essentially it would be better to be as close as possible to the middle (sweet spot) of the lens. It also is better for the springs holding the inner tube to not be compressed so much all the time.

That said, at 35MOA, you kiss the 100 yard zero goodbye and the 300 yard is near the full compression but the other way.

In my March-X scope, I have 60MOA of elevation and I start with a 20MOA ramp. So that gives me 10 down and 50 up. I need about 30 from a 100 yards to get to 1000. That leaves about 17 up or not full compression on the springs.

Now, understanding that the ONLY lens on which the inner tube will move from optical 0 is the objective lens, 13 (33-20) MOA on that lens is about .02 inch from center. I'm using 5.6 inches as the distance from the objective to the inner tube. If we change to millimeters, the focal length used is 144mm and the displacement at 13MOA is about .6mm.

Boy, I sure hope I have the calculations correct, trigonometry can be a bear.

Math and calculator wise it looks like adding 7.5 back into the cant will put me at 12 minutes either way. How does that sound?

 

[Turbulent Turtle]

Download this document from Burris:
https://www.burrisoptics.com/sites/...ew/downloads/xtrsignatureringsinstruction.pdf

You will see the chart to which I alluded earlier. The distance 4.75" seems to be the easiest one to work with. You can easily take 10MOA off the 35MOA ramp and make it a 25MOA rail.

This would make the adjustment range from -2.5 to 52.5MOA or some such.

This means that a 100yard zero would be pretty much at the bottom of the travel, but achievable. A 600 yard zero will be about 1/3 away from mechanical 0 and a 1000 yard zero will be about 1/3 up from the mechanical 0. So yeah, about 10MA down for 600 and 10MOA up for 1000. Close enough.

 

[libertyman777]

Download this document from Burris:
https://www.burrisoptics.com/sites/...ew/downloads/xtrsignatureringsinstruction.pdf

You will see the chart to which I alluded earlier. The distance 4.75" seems to be the easiest one to work with. You can easily take 10MOA off the 35MOA ramp and make it a 25MOA rail.

This would make the adjustment range from -2.5 to 52.5MOA or some such.

This means that a 100yard zero would be pretty much at the bottom of the travel, but achievable. A 600 yard zero will be about 1/3 away from mechanical 0 and a 1000 yard zero will be about 1/3 up from the mechanical 0. So yeah, about 10MA down for 600 and 10MOA up for 1000. Close enough.

Very cool. Thanks much!!

 

[Turbulent Turtle]

You're welcome. Make sure to recheck all the math.