What is Bottom Metal?

Glad you asked! 

"Bottom metal" refers to the metal (or plastic) components on the underside of a rifle that contain or retain the magazine, trigger guard, and other related mechanisms. 

It’s worth mentioning that some rifles have a “blind” magazine. In this case, the only components you’ll see under the rifle are the action screw heads and a trigger guard. With a blind magazine, the internal magazine is only accessible through the open action. There is no bottom metal on a rifle with a blind magazine. 

Seen here is a Remington 700 with an AGC Composites stock featuring a “blind” magazine. 

In any scenario other than a rifle with a blind magazine, the action screws run through the bottom metal, through the stock, and terminate in the rifle receiver/action. 

Aside from a blind magazine, there are two common types of bottom metal found on modern bolt action rifles: 

Seen here is an AG Composites short action hinged floorplate bottom metal. 

1. Internal Magazine Bottom Metal/Hinged Floorplate: This design, which is often referred to as “BDL bottom metal” has a non-removable magazine that’s loaded from the top. The floorplate can be opened to rapidly unload the magazine. The spring and magazine “follower” (which is the piece that moves up the magazine ahead of the spring and is in direct contact with the cartridges) are very similar to those found in a blind magazine. Some gun owners, hunters especially, prefer internal magazines over detachable magazines because they are typically lighter and more streamline, which can make the rifle more pleasant to pack or carry.

   

   Seen here are AG Composites long action and short action detachable magazine bottom metal. 

2. Detachable Magazine Bottom Metal: This design allows for the use of removable magazines, making it easier and faster to reload. The bottom metal contains the spring and follower. The advantages of a detachable magazine include the ability to select magazines of various capacities and the ability to change magazines rapidly, facilitating faster reloads. When hunting from a vehicle, some firearm enthusiasts appreciate the ability to pull the loaded magazine out of the rifle quickly before getting into the vehicle, instead of dumping loose rounds into a pocket. 

AG Composites manufactures rifle stocks compatible with all three magazine types: Blind, Internal/Hinged Floorplate, and Detachable. We also manufacture high-quality, billet aluminum bottom metal. Our detachable magazine bottom metal is compatible with AICS-style magazines. 

Now, from here forward, it can get a bit confusing because not all hinged floorplates are shaped the same and not all Detachable Magazine bottom metal is shaped the same. In fact, they can be shaped very differently and require the stock manufacturer to inlet specifically for the type of bottom metal. 

With that said, there has been some attempt across the industry to standardize on bottom metal shapes, or “footprints.” The most common bottom metal footprints are Remington DBM, Remington BDL, and M5. At AG, what we did was make a BDL (hinged floorplate) and a DBM (detachable magazine) that both use the M5 footprint. 

Keep in mind that if you’re building a rifle on a receiver/action other than a Remington 700 or 700 clone, you will need to specify this when ordering a stock, just as you will need to specify the action/receiver inlet. For example, Remington or M5 bottom metal will not fit a Savage stock. 

Before ordering a custom stock, it’s critical to determine the brand and footprint of the bottom metal you wish to use. In recent years, M5 bottom metal has become quite prevalent. That’s because many bottom metal manufacturers offer hinged floorplate and detachable magazine options in the M5 footprint, just as we do. 

Even so, not all M5 bottom metal manufacturers machine their M5 options to the exact same specifications. Some are a little larger, a little smaller, or potentially deeper or shallower. Again, when ordering a stock, it’s important to make note of the bottom metal brand you intend to use if it’s from a manufacturer other than AG Composites. 

Some stocks "hold" the bottom metal better. Larger, high-volume stocks with more material typically allow bottom metal to sit flush better than ultralight, low-volume stocks. Bottom metal may sit proud on a smaller stock. Some people mind this, others don’t. Either way, a qualified gunsmith may be able to machine the bottom metal or stock to meet your demands if so desired. 

Feed issues can arise with any bolt action firearm, whether it’s a stock factory rifle, a factory rifle with a custom stock, or a full custom build. This is especially true of modern cartridges that have sharp shoulder angles. 

This issue can typically be resolved by a competent gunsmith. Sometimes it can be solved very easily at home. We've seen issues where the magazine spring has lost some of its tension, resulting in the last round not rising high enough to engage with the bolt on its forward stroke. If this occurs, try stretching the spring a little and re-installing it. This often fixes the issue. 

Another issue that can arise if the magazine is not seated quite deep enough into the stock. This, too, is usually a simple fix. Sand a little material out of the stock inlet to allow the bottom metal to sit deeper in the stock 

Another thing to note: all detachable magazines have some play/wiggle. Magazines must be smaller in all dimensions than the receiving bottom metal, otherwise they’d be extremely difficult to insert into the bottom metal. This “wiggle room” is unavoidable, and how much room is between the magazine and the bottom metal varies from manufacturer to manufacturer, not just of the bottom metal but also the magazine. 

If you’re building a hunting rifle and are extremely sensitive to this, we suggest using hinged floorplate/internal magazine bottom metal.