Rifle Scopes Scope mounting - plum, level, square and offset.

[Jack Master]

So after reading 400(ish) posts about scope mounting and leveling I had to do the math.

Every time a scope mounting or leveling thread is posted it usually leads to conversations about weather the rifle needs to be level when the scope is mounted level. And sometimes is goes into weather the scope needs to be mounted directly over the bore and not offset from the bore. Well, math 'never' lies. So... attached is a sheet I put together for the down range effects of...1) mounting your scope with an offset from the bore, 2) mounting the scope level with the rifle not level, and 3) effects of a canted reticle dues to not being mounted correctly or canting the entire system.

I was very surprised to find the offsets due to mounting or rifle cant (with level scope) are very minimal. especially when compared to the canting of the scope. I could understand needing to worry much more about the offsets when shooting over... maybe 3000 yards, but even then its a strech then compaired to wind calls or actual scope cant.

Conclusions:
We need to have a level reticle or level tracking (not always the same) but don't fret over the mounting offsets (case 1) or canting the rifle with a level scope (case 2). Do worry about canting the scope.

 

[EastCOYotes]

Good work putting this together man. As an engineer I can appreciate when someone actually quantifies stuff like this.

 

[LastShot300]

Great work thanks for sharing!!

 

[Nik H]

It is good that you did this to convince yourself. I did the same exercise a while ago when @lowlight posted a thread about it.

Math don't lie...

Problem is try to convince people....LMAO.

 

[Lowlight]

People don't understand this and it goes beyond the math to the science of the brain

We cant subconsciously, 99% of the shooters out there have no clue they are doing it. Yet they are, even if they do own or attempt to use a level. Because they don't understand the medical side, they just look at the setup side of things.

Of course, the math does not lie, but at the same time, there is a WHY to all this and it's the brain.

Setting a rifle up that goes against the brain is worse than setting it up with a slight cant from the start.

 

[smoothy8500]

Just out of curiosity, why aren't 3 or 4-way adjustable buttplates more popular? Cant, offset and height are adjusted to fit the anatomical features of the shooter without putting any cant on the rifle itself? I know it's apples and oranges, but a Palma rifle is fully adjusted to eliminate the awkward position that prone with a sling introduces to the rifle.

 

[Eric32]

I believe the issue is shooting both left and right handed.

 

[Lowlight]

the left \ right issue is a cop out,

The number of support side shots taken is minor,

AI have the adjustable butt plates, its a lack of understanding and simply doing things as they always have.

Incest in the industry is the real reason if more people had a traditional background like Palma you'd see more of it.

 

[Eric32]

Frank,

I shot Palma for a while back in the day at Blakley,GA but that was short lived after the EPA shut it down then it re-opened. So I understand the need for a 4-way plate.

I would think even tho competition are limited in weak side shooting. Your only limited by your personal training regimen.

I remember the podcast you did a while back. The frist 3 or 4 rounds are mine and the rest you can do what you want. I follow that, so thanks.

I dont shoot in the PRS events. But I am a big fan of the bucket list matches such as the Guardian.

Off topic, thanks for your podcast. I hope to attend one of your classes at treadproof.

 

[bkincaid]

Can't believe you posted this in May and I'm just now seeing it.....

Thank you for taking the time to do the math, helps my understanding a whole bunch!

 

[_Windrider_]

I’m not gonna say shit. Every time canting comes up it turns into a shit show. But once again, very nice work. I’ll be over here with my badger dead level and a plumb bob.

 

[barronian]

nice, neat, concise - thanks

 

[Long Range 338]

thanks for the visual aids, they help the mental impaired like me

 

[prwillard2]

Bump for sticky

 

[theLBC]

thanks for the work!

 

[ZY100]

Ok, I think I just had a significant revelation....at the risk of doing math in public.

Please check my thought process....make sure I am connecting the dots right (ha ha).

- "Effects of canting the scope and rifle together" i.e: Scope not mounted plumb or natural hold not plumb
- Lets assume 3 degree cant for either of the above reasons
- Lets assume ~ 850 yd target, about 6 Mil for a 6.5/140gn
- Your vertical (aka elevation) induced error woudl be 0.31 Mil
- Your horizontal (aka windage) induced error would be 0.31 Mil

I THINK most people (including me ) would underestimate the minor cant impact on elevation...but the math doesn't lie. Being off on windage a few tenths at distance...chalk it up to wind. But...how many times do you think people tweak their ballistic solver to get the elevation to match, when they really might actually be canted a degree or two? Yes, I know this is why a level is important...but just saying.

Thx Jack Master....

ZY

 

[prwillard2]

Ok, I think I just had a significant revelation....at the risk of doing math in public.

Please check my thought process....make sure I am connecting the dots right (ha ha).

- "Effects of canting the scope and rifle together" i.e: Scope not mounted plumb or natural hold not plumb
- Lets assume 3 degree cant for either of the above reasons
- Lets assume ~ 850 yd target, about 6 Mil for a 6.5/140gn
- Your vertical (aka elevation) induced error woudl be 0.31 Mil
- Your horizontal (aka windage) induced error would be 0.31 Mil

I THINK most people (including me ) would underestimate the minor cant impact on elevation...but the math doesn't lie. Being off on windage a few tenths at distance...chalk it up to wind. But...how many times do you think people tweak their ballistic solver to get the elevation to match, when they really might actually be canted a degree or two? Yes, I know this is why a level is important...but just saying.

Thx Jack Master....

ZY

I am a huge fan of this document. However, am I the only one who gets twitchy when we use yards, degrees, and mils all in the same formulas? The amount of cant can be determined in mils as well, distance in meters. Maybe it's just me.

Great work by the author, the mathematical formulas are too much for me to determine, just wanting to keep the units the same.

 

[Dthomas3523]

I am a huge fan of this document. However, am I the only one who gets twitchy when we use yards, degrees, and mils all in the same formulas? The amount of cant can be determined in mils as well, distance in meters. Maybe it's just me.

Great work by the author, the mathematical formulas are too much for me to determine, just wanting to keep the units the same.

It’s just you. The distance units don’t matter at all since we are discussing angular measurements.

 

[Dthomas3523]

The only things I’d recommend people to keep in mind is if possible, learn to shoulder most rifles without canting and then needing to have the optic level with rifle canted for a few reasons:

1: easier to set up all rifles level/level

2: easier to shoot other rifles that may be set up level/level (good example is shared work/duty rifles, or school house rifles).

3: if shooter is a beginner, they may improve their fundamentals, start shouldering the rifle more level, thus throwing off the reticle level now. So, new shooters with canted rifle/level reticle setups need to be conscious of their position changing over time.

I’d say, whenever possible, have a level rifle/level reticle and only use canted rifle/level reticle when it’s been absolutely determined this is the best setup for the shooter.