Mossberg 100 ATR LA

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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

Mossberg 100 ATR in .270 Win.

Figure 1: Mossberg 100 ATR in .270 Win. (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 (LA) Calibers

Long-action Mossberg 100 ATR can be chambered for:

.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

Most variants came with a 2-piece Weaver base pre-installed, but the receiver is drilled and tapped so the owners can swap bases according to their liking.

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

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

Mossberg 100 ATR SA

These are the receiver dimensions of the long-action Mossberg 100 ATR:

A: 21.9 mm

B: 119.4 mm

C: 15.3 mm

BHU: 2.9 mm

Fi: 6-48

R1: R60

R2: R17

Scope Mounts Interchangeable with Mossberg 100 ATR (LA)

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

The necessary condition for rifles to have one-piece scope mounts interchangeable is that the mounting surfaces of these rifles match in every dimension.

These are the rifles that have one-piece scope mounts interchangeable with the long-action Mossberg 100 ATR:

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

For two-piece scope mounts to be interchangeable, the mounting surfaces of the rifles must match in every dimension except the action length which can vary. This is because the distance between the two pieces of the mount is not fixed.

Rifles that have two-piece scope mounts interchangeable with the long-action Mossberg 100 ATR are the following:

Best Scope Mounts for Mossberg 100 ATR (LA)

Fixed Scope Mounts for Mossberg 100 ATR (LA)

When looking for a fixed scope mount for any US-made rifle, we often first look towards DNZ. They make excellent products and are extremely reliable.

We would recommend this DNZ Game Reaper 30mm fixed scope mount for your long-action Mossberg 100 ATR:

Detachable Repeatable Mounts for Mossberg 100 ATR (LA)

In case you are looking to mount a detachable repeatable scope mount on your Mossberg 100 ATR, then we would recommend this 30 mm EAW pivot mount:

Picatinny Rails for Mossberg 100 ATR (LA)

When you’re looking for a Picatinny rail for your rifle, you need to pay special attention to the length between the rear and front holes on the receiver (distance B in the image above). We recommend this EGW Picatinny rail for your Mossberg 100 ATR (LA):

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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Mossberg 100 ATR LA

Sub Categories

The History of Mossberg

Mossberg 100 ATR Rifle Review

Mossberg 100 ATR (LA) Calibers

Mossberg 100 ATR Variants

Scope Mounts Interchangeable with Mossberg 100 ATR (LA)

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

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

Best Scope Mounts for Mossberg 100 ATR (LA)

Fixed Scope Mounts for Mossberg 100 ATR (LA)

Detachable Repeatable Mounts for Mossberg 100 ATR (LA)

Picatinny Rails for Mossberg 100 ATR (LA)

Help Us Build Our Riflescope Mounts Database

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