Over the last decade, there has been a stark increase in the number of recreational shooters in the United States. Customizing a new AR-15 can be one of the more enjoyable hobbies to undertake, as there are countless options available on the market to choose from. The AR-15 is a versatile weapon, and with the inclusion of modern rail systems like MLOK, the ways an end-user can adjust subtle details to impact the overall functionality of the firearm are endless. One of the first options most users will need to determine is the caliber of ammunition the rifle will utilize. There are a number of options to choose from in this area, and each offers its own unique advantages.

The First Round For The AR-15 - 5.56x45

5.56x45 - The most common round for the AR-15 platform, the 5.56x45 has been the standard for over 60 years. It was developed in the 1960s as the U.S. Military was looking for a more reliable, accurate, and lighter general issue weapon and cartridge. Before this, NATO was looking for a single rifle cartridge that could be adopted for use by all of the allies so that if war happened again, these rounds would be easy to distribute and produce by everyone. At the time the AR-10 was developed into the M16 and then the AR-15 was developed. The U.S. Military adopted the 5.56 as its round of choice, so ARs began to be made with these as well. 

.300 Blackout - Accuracy Above All

.300 Blackout - The .300 Blackout is also commonly known as the .300 BLK or as the 7.62x35mm. This Ar 15 caliber was designed to be usable on existing AR-15s that were chambered for the 5.56, but could be a heavier, more intermediate cartridge. The goal was to be similar to 7.62x39mm but still be usable in existing AR-15 magazines. This caliber is very accurate and loses very little velocity when fired. However, it can be very expensive and hard to find. Plus, it's not the best for long-range shooting.

6.5 Grendel

6.5 Grendel - Also known as the 6.5x39mm, the 6.5 Grendel is very similar to the .300 Blackout. It was designed to be highly accurate and have low recoil. This round is shorter than others with a larger diameter case so that it can fit into the 5.56 AR-15 magazines. This caliber is better than the 5.56 with better terminal energy and range. However, it is not always reliable in a 5.56 magazine and won't feed the best. Plus, you may want to switch out your upper receiver for this caliber, but it will still be compatible with a 5.56 lower.

What Is The Goal For Your Rifle Build?

When it comes to caliber, RailScales recommends considering power, availability of your chosen cartridge, and the cost. Will you be hunting, shooting in competitions, or investing in self-defense? There are many factors to consider when building a custom AR-15, taking into account that the more popular calibers like 5.56x45 offer a more diverse array of accessory options. RailScales continues to show that finding functional solutions to common problems for shooters can drive product innovation. When looking for new AR 15 accessories, RailScales can be counted on for creating excellent new products and/or rifle accessories that are aesthetically pleasing to look at and give a clean and low-profile product that enhances many aspects of shooting. Regardless of the choice in caliber, RailScales offers the best rail covers to make your shooting time comfortable and easy.