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A Tool & Die Machinist’s Review Of

The “Cold Shot LLC” “MilliRadian Adjustable Scope Base

(MRAB)

By: Kris Norman

Foreword:
I am a Prototyping Tool & Die Machinist with over 20 years of experience in machining and metrology. I’m
also a firearms enthusiast, a hunter, and an avid long range target shooter. At the request of Lawrence at Heritage
Arms, I conducted a professional analysis of the MRAB on an impartial basis – both upon my impressions as a
machinist and shooter, as well as its technical accuracy and precision based upon my expertise in metrology. I
conducted the technical analysis in a Q.C. Lab, on a CNC Coordinate Measuring Machine, which is traceable to NIST,
and has been certified accurate to within 0.00005” on all axes.
 
The Realization of MRAB
There are few times in life when a groundbreaking idea for an invention comes to mind. To find
that someone else has beaten you to the punch is usually a disappointment. However, about a year ago
when I came up with a concept for a sine-adjustable scope base, and later discovered that a gentleman
named Lawrence, and his team at Heritage Arms had already designed, patented and created the
concept; rather than being disappointed, I ultimately ended up being supremely impressed.
I have to admit that being a precision craftsman – and a perfectionist, I was skeptical at first that
the MRAB would be of as high of a degree of quality, rigidity and accuracy that would be required for
extreme long range shooting. So, I emailed Lawrence with a series of technical questions about the
MRAB in order to gain an understanding of just how precise his device actually was. When I found his
answers to exceed my expectations, I knew then that I HAD to get my hands on one!
 
72MIL’s Of Elevation Adjustment
If you’re proficient at converting MIL to MOA, then you know that’s over 247MOA. To put it in
simpler – albeit more amazing terms…This means that you can dial in a 1Mile+ shooting solution on a
standard .308WIN rifle, which is set at a 100yd zero!!! Nothing else needs to be said about the MRAB’s
range!
 
Good Looks And More
Once in hand, it didn’t take me long to see that the MRAB is craftsmanship at its very best.
From the beautiful machining, flawless fit and finish of the critical components, and almost unbelievable
rigidity, it transcends the realm of mere craftsmanship - to a precise, functional, mechanical work of art.
The jet black hardcoat anodizing, contrasted by the beautifully laser etched text and graphics, make the
MRAB aesthetically pleasing – not to mention MEAN, imposing, and authoritive when mounted upon a
rifle. For some people, the MRAB could be mis-categorized into the class of “Tacticool”, but unlike most
components of that category, it’s cool with a purpose, and tactical with actual precision. A better
comparison for the MRAB would be to a fine timepiece…ultimate accuracy and precision, encased within
a beautiful, functional, and stylish package that you’ll want to show off.
 
Unique, Groundbreaking And Ingenious Features
 
Anti-Backlash and Repeatability: Two reasons why high-end scopes are so expensive, and why
cheaper scopes aren’t as accurate. These are two areas, amongst many, where the MRAB performs
exceedingly well. (Backlash is the necessary clearance within thread engagements, which results in an
unavoidable error of difference between the actual position vs. the dialed position on a scale - dependent on the
direction you’re dialing. In simpler terms: it means that if you dial off 10MILS going up the scale, and then stop at
the same 10MIL mark coming back down the scale, your actual POI will be different because of backlash error
within the elevator screw – unless compensated for.) However, the MRAB has an anti-backlash bushing
integrated into the elevator screw, so you can be assured that whether you’re dialing up or down to
your desired DOPE, the MRAB will always be positioned exactly where it should be. This is a feature
found only on the elevator and windage turrets of optics costing thousands of dollars. So, for all the
naysayers out there who think that the MRAB won’t be as accurate at dialing in elevation as your $1,000
or $10,000 scope – you’re wrong. In fact, over time, the MRAB will be even MORE accurate than ANY
scope turret, simply because of being able to handle constant adjustment without the inception of wear
and tear on a device as fragile as an internal turret assembly. In addition, clicking off both small and
large sums of MILS on the MRAB is a quick and easy task with its large and clearly marked wheel that has
a positive indexing feel. I found repeatability specs to be +/-0.02MIL, and the linear graduated accuracy to
be from 0.00 to 0.22MIL over the entire 72MIL range.
 
A continuous, one-piece rail clamp: In a display of its extreme precision, the MRAB has no
segmentation in its rail clamping system. This means that there is no chance of mis-alignment when
mounting the MRAB to your rifle’s MIL-STD Picatinny Rail. In all my years of shooting and mounting
scopes, I’ve observed factory scope mounts on both entry level and high-end rifles alike to be out of
alignment to the bore on average around .002”, with the worst offenders being around .015”. An optic
being slightly off-center to the bore only causes a negligible effect…as long as the centerline error
remains parallel to the bore axis. But, an optic being out of parallelism to the bore axis is a critical
failure. This was a concern of mine with my initial questions about the MRAB. However, I was
extremely pleased and impressed to find that the MRAB’s two picatinny rail surfaces (one male and one
female) are on center to each other within .0005”, and parallel within .0002” throughout their entire
range. This supremely accurate alignment of the machined surfaces on the MRAB ensures that as long
as your bottom mounting surface is accurate to your rifle’s bore, the MRAB will be just as precise.
 
A moving apparatus with ultimate rigidity: Continuing the MRAB’s display of precision and
accuracy, I had to double-check my results when I measured the axial rigidity throughout the elevation
range. Over the entire 72MIL range, the position of the moving rail did not shift from side to side in an
amount greater than .0001”. In addition, it took 45lbs of direct pressure applied to the side of the
moving rail at its highest indexed point to deflect it. Furthermore, even with 100lbs pressing onto the
moving rail, it had zero deflection in its elevated position. So, all of you who may be concerned that
your big bore rifle will cause the MRAB to move under heavy recoil can rest easy knowing that it will be
as rigid as the mounting surface it is placed upon.
 
Summary: The MRAB - Precision Metrology For Your Optics
Make no mistake; The MRAB is the real-deal! With its enormous range, ease of use, accuracy
and rigidity, I foresee the MRAB making its way onto our brave military’s long-range arms VERY soon.
Without hesitation, I would recommend the MRAB as a MUST HAVE for any serious varmint hunter, or
long range/competition target shooter.