Building with a Parts Kit for an AR-15? Upgrade These Parts

Building with a Parts Kit for an AR-15? Upgrade These Parts

May 9th 2024

The great thing about building with a gun parts kit is that a lot of them have everything you need - literally - minus the frame or receiver.

This makes them sort of foolproof. There’s no way to forget to get an essential part. Everything’s right there in the kit. Granted, you have to know how to assemble it, but that’s a different story.

Now, we have to publish a caveat here. Just because a gun parts kit for, say, an AR15 platform has everything you need minus the lower, that doesn’t mean the parts are great.

Meaning you’ll be able to build a functioning rifle, but will it be the best it could be? Not necessarily. Mil-spec certainly doesn’t mean “best.” A lot of people don’t get that. With that said, here are some of the parts you should consider replacing, even if they come with the kit.

Bolt Carrier Group

Arguably one of the most impactful parts to replace in any AR15 kit. Sure, the kit will come with one, but most come with a mil-spec, phosphate-coated BCG.

Nothing against the phosphate coating. It is durable and wear-resistant, and with proper care, will last a long, long time.

The thing is, phosphate coatings have a bit of tooth, and therefore they need a little extra liquid lubrication to stay limber. That extra liquid lube traps dirt, dust, and fouling, which counterproductively accelerates wear.

The modern market abounds with better alternatives, with modern, advanced coatings that offer superior permanent dry lubricity, like black nitride, nickel boron, titanium nitride, and diamond-like carbon, or DLC.

All of these (and others) require less liquid lubrication and are easier to maintain and clean than phosphate, minimizing wear and improving cycling performance.

                        Muzzle Device

Muzzle Device

There is a good chance your AR15 kit comes with a muzzle device and that moreover it is some sort of birdcage-style flash hider.

Flash hiders are great. They keep the muzzle flash from blinding you so you don’t get your sight picture clouded.

But are they the best muzzle devices? In our estimation, hardly. There are way better ones, and our vote goes for muzzle brakes.

The reason for this is that muzzle brakes do (mostly) what flash hiders do and then some. The real draw of a muzzle brake is that it will vastly reduce felt recoil, by 50% or more. When shooting an AR chambered in 5.56, you will barely feel it.

Plus, if your barrel is already threaded, making this swap is a cinch.


This is not a huge deal but if your AR15 gun parts kit comes with a fixed stock, it’s probably worth replacing it with a folding or adjustable replacement, specifically one that is lightweight, even skeletonized.

This simple upgrade will improve handling and adjustability, making it easy for you to make quick changes to LOP and possibly even comb height that are necessary when you’re wearing different clothing throughout the year.


Mil-spec triggers, like mil-spec bolt carrier groups, are just average. They work, but mil-spec triggers just aren’t precision triggers. In some instances, they can feel downright gritty.

There are far, far better triggers on the market nowadays than mil-spec standard trigger groups, even frictionless triggers that offer zero-creep and which are as crisp as a cool fall morning.

TriggerTech Triggers, which use FRT, or “Frictionless Release Technology” come to mind. But that’s just one drop in the bucket. Other great triggers include CMC, Timney, ALG, Rise Armament, and Geissele triggers.

Charging Handle

This one’s a bit iffy - there’s nothing wrong with mil-spec charging handles - not necessarily, at least.

At the same time, mil-spec charging handles favor right handed shooters, which can be problematic for southpaws (although, the forward assist is also right-biased, so if you’re left handed you might have bigger problems than the charging handle).

At the same time, there are ambidextrous charging handles that are oversized (making it easier to work them intuitively in the dark, or in the cold when wearing gloves), and some even port gasses away from your face - another benefit.

Maybe: Handguard

Here’s the thing. If your AR15 kit has mil-spec parts, it’s going to come with a Picatinny rail. If the platform is modeled after the M16, it will probably come with a plastic handguard known as a triangular or tropical handguard.

Some shooters take issue with both of these choices. In the case of the tropical handguard, it doesn’t offer any attachment points. It is fairly comfortable to shoot, though.

As for the Pic rail, it offers excellent expandability and versatility, as well as a great grip with gloves. The tradeoff is that Picatinny rails are really heavy and not particularly comfortable to shoot without gloves.

That leaves two big alternatives: KeyMod and M-LOK handguards and rail systems. Both are lighter than Picatinny rails, although there are fewer accessories that are compatible with them.

If the weight of a Picatinny rail is not appealing to you, consider replacing that part with either an M-LOK or a KeyMod rail system. Just be aware you will need to get compatible shooting accessories if you swap the system.

Other Parts You Might Also Want to Replace in Your AR15 Kit

While these are some of the more important parts you might want to replace in a parts kit if the stock parts won’t work for you, there are others you might want to replace, too. Consider replacing these as well:

  • Trigger guards (oversized are a good replacement)
  • Magazine releases, bolt releases and safety selectors (ambidextrous-friendly)
  • Grips, if you don’t like the standard grip that comes with the kit.
  • Backup sights (offset sights are a good mod, though not a replacement)
  • Gas blocks (some shooters prefer adjustability)

Start with a AR-15 Gun Parts Kit from SARCO

Getting ready to build an AR15 from a parts kit? If you’re planning on making customizations along the way, get the parts and shooting accessories you need here at SARCO, Inc. We carry  a massive inventory of gun parts and kits, including AR15 kits that contain everything you need minus the lower - so get started building today and if you have questions before you buy, contact us at 610-250-3960.