Should I buy or build an AR15-Style MSR Rifle?

April 20, 2023

Should I buy or build an AR15-Style MSR Rifle?

This topic comes up a lot on gun forums someone will ask, "I have been thinking about getting an AR-15. What should I get?" and someone will answer “build one yourself.” Even though that is a great idea, it may not be the best advice to give someone not knowing the persons skill level and familiarity with AR15s or if they even have space to build one.

Parts and Tools for building an AR15 style rifle

Why Should I buy an AR15 MSR rather than build one?

For those without the workspace tools, and time, finding the best built MSR to suit your purpose might be a better option. MSRs come in a variety of configurations. They are built by factory trained workers. and some are even factory-test-fired. They often come with warranties and carry the brand's reputation. Some brands will hold a better resale value than selling a "parts gun." One can always customize after the purchase to suit their purposes as they go which maybe a better option for many.

Stag-15 AR15 with Warne Scope Mount

Why Build an AR15 MSR when I can just buy one?

There are many great reasons to build one besides the satisfaction of building one yourself. The AR15 is easy to assemble, that is, if one knows how it goes together, operates, has the right tools, and workspace to build it. It maybe best to have a built AR15 to refer to. Many will buy their first one complete and then upgrade the parts learning how everything goes together and operates and then build one. Building your own MSRs can become an addictive hobby.

Except for installing the barrel, an AR-15 style rifle can be built on a kitchen table, provided you use something to protect the table because a hammer is involved. A workbench of some sort with a vice would be a far better choice.

There are tools needed to build an MSR. A vice, torque wrench, barrel nut wrench, small hammer, roll pin punches, an action block or a reaction rod, and eye protection. There are some special tools that are not needed but will make it a lot easier, like a take-down pin installation tool, slave pins for the hammer and trigger, a gas tube alignment tool, and a gas block dimple tool. 

Basic Tools for building an AR15

Building a purpose-built MSR

One may not find the exact rifle with all the features they want prebuilt, so they end up paying for parts they didn't want. A purpose-built rifle means that the builder has a specific purpose for the rifle. They may want something short-range for tactical purposes and build it to shoot 9mm instead of 5.56. They may prefer M-LOK over a Picatinny rail to attach a light. There are several stock options from fixed to collapsible with different features, forward controls and to choose from depending on the end purpose as well as many cartridge options to suit different purposes.

Or a shooter might be building one as a long-range tack driver using a longer premium barrel and fixed stock. Shooters participating in speed competitions will want parts that will increase speed because most competitors are timed. Also, there are color options other than black to personalize an MSR.

Custom Built AR15 with Warne AR15 Mount

Barrels will come in different qualities and different thickness and materials and can cost a lot of money for a really accurate one or a long lasting one and there are plenty out there that are affordable that a good enough for general purpose.

MSR barrels come in different lengths for different kinds of sport shooting but keep this in mind there are strict laws with severe penalties regarding minimum barrel length on a rifle so before you start buying parts research your state laws and federal laws regarding minimum barrel length as well as certain features that may not be legal for the build you are doing.

Building an AR-15 Style MSR can save you money

Many upgrades are available for MSRs. A shooter may wish to install a specific trigger such as a 2-stage or drop-in competition trigger. They may wish to install a Picatinny rail, a M-LOK, a Keymod, or a retro plastic handguard.

Building your own allows one to go cheap on parts that may not be as important as others. One might be able to save money on the upper and lower receivers and spend that money on a better trigger or quality scope mount for their AR-15. Also, building it oneself is like a layaway program; one can buy parts as they can afford them and assemble the MSR over several months. There is gun forum classifieds that a gun hobbyist can save money by buying good used parts.  

However, if a first-time builder gets a box of parts and has no idea how it all goes together to function correctly, they may skip something important, like proper torque on the barrel nut.

Intalling a barrel on an AR15 style rifle MSR

Common mistakes beginners make while building their first AR15-style rifle.

  • A gas tube installed backward – causing the rifle to be a single shot.
  • A hammer spring was installed backward - the gun sometimes fires, mostly light primer strikes.
  • The gas tube installed crooked - causing the bolt carrier group to jam, feed issues, and gas issues. A lot of issues can be caused if the gas tube is not installed correctly.
  • Upside-down disconnector spring causing trigger reset issue.
  • loose barrel nut - accuracy issues and depending on how loose, could be dangerous to shoot.
  • The buffer retainer spring is not installed correctly - causing the buffer to stick out, making it difficult to close the upper to the lower.
  • Misaligned gas block to gas port - causing failure to cycle or failure to feed.
  • The gas block was too loose, not dimpled, or no read locker used works its way out of port alignment – won’t cycle.
  • Forgetting to lube new parts, causing malfunctions and sluggish operation.
  • Install incorrect parts – for example using a carbine length buffer in a rifle length tube all kinds of problems.

Another thing a first-time builder should pay close attention to while installing springs and detents is to wear eye protection. There are a couple different tools made for installing the detent in the front takedown pin, which makes the task easier. There are ways to install them without the special tool, but best have a couple of spare detents because if they shoot out while installing, they can hit you in the eye or get lost. 

Installing front take down pin on an AR15

After the rifle is built, it's time to choose what kind of sight or optic you are going to use, be it iron sights or an optic, depending on your budget and the shooting you plan on doing. Check out Warne's Red Dot Risers if you decide on a red dot reflex optic. Suppose you plan or use an LPVO, or other magnified scope check out Warne's MSR Mounts

Warne 3-Gun set up.

Choosing the correct optic or sight for your MSR is a whole other topic as there are so many options out there. Some may just want to go with open sights and there are many options of open sights from the detachable carry handle to flip back up iron’s sights or side mounted sights. A lot shooters who build MSRs are looking for precision or speed. When looking for precision a Shooter will usually go with a magnified optic and when looking for speed a red dot optic or if they are going for both they may get a magnified optic and with a red dot mounted on a 45-degree mount like the photo above or an LPVO which is combines both with some limitations read more about LPVO vs Red Dot and read more about what MSR Mounts Warne offers to keep you target. Read about the best scope mounts for AR15 style rifles.