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Mossberg 100 ATR (Weaver)

The History of Mossberg

In 1919, Swedish immigrant Oscar Frederick Mossberg, aged 53, launched a journey into firearms manufacture. Alongside his sons Harold and Iver, the trio established what was originally named Mossberg & Sons, Inc., operating out of a rented loft on State Street in New Haven, Connecticut.

The company’s vision was relatively simple: to manufacture durable and reliable firearms for the working class. Their first creation was a modest 4-shot Brownie pistol in .22 caliber, paving the way for a legacy of accessible, dependable firearms.

Just a few years later, in 1922, the Mossbergs produced their first rifle, the Model K. This .22 hammerless pump repeater rifle was in fact initially designed by the famous Arthur Savage but was finalized and improved by the Mossberg team.

As the world descended into war during the 1940s, Mossberg & Sons pivoted its focus to support the war effort. Securing a government license, they began producing tolerance tooling gauges, various machine gun parts, and components of the British Lee-Enfield rifle. During this era, Mossberg also introduced the Model 42MB, a .22 training rifle for British troops. An impressive amount of 45,000 units of Mossberg Model 42MB were produced. This period not only propelled Mossberg onto the global stage but also sparked a period of significant growth for the company.

The post-war years saw Mossberg contributing to the sporadic popularity of bolt-action shotguns, as they produced an array of these firearms. However, today, the company is most renowned for its exceptional pump-action shotguns. Particularly famous is the legendary Mossberg Model 500 pump-action shotgun introduced in 1962. In 1979, the US government awarded Mossberg a contract to produce the Model 500 as a combat-duty-rated pump shotgun. This led to the Model 500 being adopted by every branch of the US Military. By 2010, 41 different variations of the Model 500 were available on the market.

The company’s influence extends beyond firearm manufacturing. Mossberg has introduced several components now commonplace in the industry. For instance, Alan Mossberg developed a safety cable lock in 1989 that now comes as standard with almost every firearm sold today.

Mossberg celebrated 100 years in 2019, and even today continues to be a family-owned and operated business.

Mossberg 100 ATR Rifle Review

All variants of the Mossberg 100 ATR rifle are drilled and tapped for scope mounts, but most of them will come with pre-installed Weaver bases or Picatinny rail.

This page is dedicated to Mossberg 100 ATR models with pre-installed Weaver bases. You can also see:

Mossberg 100 ATR in .270 Win. with factory-installed Weaver bases

Figure 1: Mossberg 100 ATR in .270 Win. with factory-installed Weaver bases (Source: Mossberg)

The Mossberg 100 ATR, a now-discontinued bolt-action rifle, offered excellent value during its production run. Known as the "All-Terrain Rifle", it was appreciated for its out-of-the-box readiness, often coming equipped with a pre-installed riflescope. The 100 ATR also had a reputation for impressive accuracy for a rifle in its price bracket.

While it's no longer in production, it sorts of lives on in the modern Mossberg Patriot rifle. A lot of Mossberg owners see the Patriot as the successor to the 100 ATR, and considering all the similarities between the two, rightly so.

Mossberg 100 ATR models feature a fluted and free-floated barrel that measures either 20 or 22 inches in length, depending on the model. The finish applied to the barrel was either Matte Blue or Marinecote.

To our knowledge, every 100 ATR came with Mossberg’s patented LBA trigger which stands for "Lightning Bolt Action Trigger". It shares some similarities with the AccuTrigger you might know from Savage rifles. One of the best things about this LBA trigger is that you can adjust it yourself. You can set the trigger pull weight anywhere between 0.9 to 3.2 kg (2 and 7 lbs) using just a screwdriver. It has a special safety feature built into it, known as a safety blade. There's a lightning bolt shape cut into this blade - hence the "Lightning Bolt Action" name. This blade needs to be fully depressed before the gun can fire. It's a simple feature that does a big job - it keeps the gun from accidental misfiring.

100 ATR’s stock is either synthetic or wooden, coming in several different finishes. The buttstock offers a comfortable rubber butt-pad to reduce recoil, especially when handling heavier calibers.

As for safety, the 100 ATR was equipped with a side lever two-position safety mechanism, which was simple and intuitive to use. Pushing the lever forward signaled the rifle was ready to fire while pulling it back set it to safe. When in firing mode, a red dot was visible as a clear visual indicator.

All models feature a top-loading integral magazine with a capacity of 4+1. It is nothing fancy, really, just a rather straightforward and simple-to-use design suitable for a budget-friendly rifle.

The 100 ATR came in two action configurations - short-action and long-action. This is just like the Patriot model, and to our knowledge, both models share the same receiver dimensions. Most 100 ATRs had a 2-piece Weaver base factory-installed, but some came with a Picatinny rail instead. You could swap these scope bases out if you wanted to, as the receiver is drilled and tapped.

As mentioned above, 100 ATR often came pre-equipped with a riflescope when purchased. This was usually a simple 3-9x40 scope without any fancy stuff, just a simple plain cross. The idea was simplicity and functionality without any unnecessary extras.

Mossberg 100 ATR Calibers

Mossberg 100 ATR can be chambered for:

.243 Win.
7mm-08 Rem.
.308 Win.
.270 Win.
.30-06 Spring.

Mossberg 100 ATR Variants

Mossberg 100 ATR was sold in several different variants. Below you will find the ones we were able to track down. If we missed any, please let us know at info@optics-trade.eu:

Mossberg 100 ATR Scoped
Mossberg 100 ATR Synthetic Black
Mossberg 100 ATR Mossy Oak Break-Up Infinity
Mossberg 100 ATR Mossy Oak Brush
Mossberg 100 ATR Real Tree Xtra
Mossberg 100 ATR Walnut
Mossberg 100 ATR Tree AP
Mossberg 100 ATR Youth
Mossberg 100 ATR Super Bantam Muddy Girl
Mossberg 100 ATR Super Bantam
Mossberg 100 ATR Super Bantam Scope Combo
Mossberg 100 ATR Bantam
Mossberg 100 ATR Mossy Oak Deer THUG
Mossberg 100 ATR Night Train
Mossberg 100 ATR Trophy Hunter

The drilled and tapped receiver of the long-action Mossberg 100 ATR with pre-installed Weaver bases

Figure 2: The drilled and tapped receiver of the long-action Mossberg 100 ATR with pre-installed Weaver bases (Source: https://www.icollector.com/Mossberg-100-ATR-270-Win-SN-BA158339_i33327249)

Scope Mounts Interchangeable with Mossberg 100 ATR (Weaver)

Rifles That Have One-Piece Scope Mounts Interchangeable with Mossberg 100 ATR (Weaver)

The necessary condition for rifles to have one-piece scope mounts interchangeable is that the mounting surfaces of these rifles match in every dimension. This means that any rifle with Weaver bases will have one-piece scope mounts interchangeable with Mossberg 100 ATR which has the same scope mounting solution.

Rifles That Have Two-Piece Scope Mounts Interchangeable with Mossberg 100 ATR (Weaver)

The situation with two-piece scope mounts is the same as with the one-piece scope mounts when it comes to rifles that are equipped with Weaver bases.

Any rifle with Weaver bases will have two-piece scope mounts interchangeable with the Mossberg 100 ATR which has the same mounting solution.

Best Scope Mounts for Mossberg 100 ATR (Weaver)

Fixed Scope Mounts for Mossberg 100 ATR (Weaver)

Henneberger is a German company known for the quality and reliability of its products. If you are looking for a fixed scope mount to mount on a weaver base on your Mossberg 100 ATR (Weaver), then we recommend these Henneberger’s 30 mm Weaver rings. They are made of aluminum and come with a 30-year warranty.

Detachable Repeatable Scope Mounts for Mossberg 100 ATR (Weaver)

When it comes to flexibility, detachable repeatable scope mounts are the way to go. Being able to easily attach and detach an optic without any tools and retaining zero at the same time can be a great advantage.

If this is what you’re looking for, you might want to consider this INNOmount Two-Piece Mount for Weaver/Picatinny of German quality for your Mossberg 100 ATR with Weaver bases.

Help Us Build Our Riflescope Mounts Database

If you happen to own this or any other rifle, we would appreciate it if you could help us expand our database by sending us some photos of the rifle receiver (the bare mounting surface of the rifle without the mounts installed). For your help, our company offers a fair return in terms of practical rewards.

Please send us an email for more information. You can contact us here: info@optics-trade.eu

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VIDEO

Introduction

In recent years we can observe that a trend of Picatinny rail has become widespread and global. It is driven by the NATO standardized rails, more commonly known as the Picatinny rail standard. Picatinny rail being the New Jersey Arsenal that developed it in 1995.

These mounting options are revolutionary. The biggest and best advantage being that the Picatinny rail can be used its entire length and not bordered to a few pre-designed slots like for example the Weaver rail standard was before.

The other main advantage is the ease of use and interchangeability. If a product is meant for a Picatinny rail design it will fit all Picatinny-rails, no matter the manufacturer or date of production.

Picatinny/Weaver Rail

Picatinny Rail and Weaver rail profile

Design

The Picatinny rail is almost exclusively crafted from a single piece of metal (in some cases aluminum). In this manner, the axis of the Picatinny rail is perfectly straight and aligned with the axis of the firearm. Therefore the rifle scope which is mounted onto this kind of configuration is certainly aligned with the rifle / gun and the trajectory of the ammunition.

Weaver rail design on the other hand is usually manufactured in two separate pieces, greatly increasing the possibilities for the axis to be crooked, overlapping, and out of line.

It is always harder to align two separate pieces to a third line than it is to align one piece to another. In this way, the lapping of two mounting rings on a single-piece Picatinny rail is no longer required.

The single-piece rail will assure that both rings are perfectly aligned to each other and that no unwished stress is transferred to the riflescope.

Picatinny compare to Weaver Rail

The Picatinny rail itself is an evolutionary step forward from the older Weaver rail. The main difference between Picatinny rail and Weaver rail is the spacing of the slots. Picatinny rail design has them evenly placed exactly 5.23 mm from one slot to the other, 3 mm deep. For this reason, the mounting options are repeatable and the same as other firearms using the Picatinny rail standard.

Interchangeability was a major driving force in the development of the new standard as different NATO armies need to be compatible with each other.

Weaver rail has 3.8mm wide slots and these slots can be placed anywhere on the Weaver rail and in any number that the producer wished.

Advantages of Picatinny design

A big advantage for using the Picatinny rail design is the ever-present recoil stop. Furthermore, the manufacturing of the rail is not very technically demanding and can be done without the use of state-of-the-art machines which greatly reduces the cost of the finished product, making it very affordable.

The Picatinny rail is easy to mount and usually, this type of configuration does not transfer negative stresses and forces from the fired weapon to the rifle scope.

In addition, the Picatinny rail with its very long useable surface works well for mounting longer rifle scopes or to achieve optimum eye relief.

The durability and toughness are other big pluses for this solution.

Manufacturers of Popular Models

A majority of the Picatinny rings are fixed, but a number of best rated European manufacturers (EAW, MAK,..) have, in recent years, put a lot of effort into the development of detachable ring with100% repeatability, with which it becomes easy to remove the scope from the weapon without the use of tools.

No re-zeroing is needed with such mount options, but these models tend to be expensive.

Weaver and Picatinny Rings

Picatinny rail and weaver rail share one more thing. It is possible to use the Weaver ring and the Picatinny ring on the Picatinny-rails, but it is usually impossible to use the Picatinny ring on the Weaver base. The reason being the above-mentioned positioning and spacing of the slots.

Picatinny mounts have a 5mm recoil stop that goes into the rail slot and since
Weaver rail only has 3.8mm wide slots such rings do not fit on Weaver rails.

Due to this reason, the Picatinny-rails are popular and prevailing on the market in recent years and eventually, these options will completely oust the Weaver rail from the market.

Mossberg 100 ATR (Weaver)

The History of Mossberg