GunPartPicker: A PCPartPicker for Guns

Yes, It Exists. And It's Free.

If you've ever Googled "PCPartPicker but for guns," you already know the frustration. You want to build an AR15 from parts. You want to pick components slot by slot, compare prices across stores, check that everything fits, and get a parts list you can actually share. PC builders have had that for over a decade with PCPartPicker. Gun builders? Not so much.

Until now. GunPartPicker is a free AR build tool with 30,000+ products from 500+ brands across 50+ categories, with live pricing from 30 retailers. Pick your upper, lower, barrel, BCG, handguard, trigger, optic, and everything else. Get real prices, compatibility checks, and a shareable link. That's it. That's the tool.

What's Built In

Here's what GunPartPicker ships with out of the box:

✓ Slot-by-slot part selection across 50+ product categories ✓ Live pricing pulled from 30 firearms retailers ✓ 15,000+ products currently in stock and tracked ✓ Automatic compatibility checking for caliber, platform, gas system, and thread pitch ✓ Shareable build links you can post anywhere ✓ Real-time in-stock and out-of-stock tracking ✓ Running price total that recalculates as you swap parts ✓ Search and filter by brand, price, and specs across 500+ brands ✓ No account required to build, compare, or share ✓ Works on mobile and desktop ✓ Save builds to your account and access them from any device

How the Builder Works

If you've used PCPartPicker, this will feel familiar. If you haven't, it's pretty straightforward.

You get a set of component slots. Each slot represents one part of your AR build. Click a slot, browse or search products in that category, pick one, and it drops into your build. The price total updates, compatibility gets checked, and you move to the next slot.

The whole thing takes about five minutes for a full build. Here's the slot breakdown:

Receivers and Barrel

Lower Receiver is where you start. This is the serialized part, legally the firearm. It also locks in your platform: AR15, AR10, or AR9. Every compatibility check after this point references the lower.

Upper Receiver has to match your lower's platform. An AR15 upper on an AR15 lower. Simple.

Barrel sets your caliber, accuracy ceiling, and gas system length. GunPartPicker currently tracks 1,861+ handguards and 3,268+ upper receivers in the catalog, so you've got options.

Bolt Carrier Group needs to match your barrel's caliber. 5.56 BCG for a 5.56 barrel, .308 for .308, 9mm for 9mm.

Internals

Trigger can be single-stage, two-stage, or a drop-in cassette. Biggest single upgrade you can make to any AR.

Charging Handle comes in standard or ambidextrous. Most builders go ambi.

Gas Block is either low-profile or adjustable. Adjustable lets you tune for running suppressed vs. unsuppressed.

Furniture and Muzzle

Handguard needs to clear your gas block and barrel nut. M-LOK has basically won the rail wars at this point.

Stock is fixed, collapsible, or adjustable. Make sure your buffer tube spec matches (mil-spec vs. commercial).

Pistol Grip is personal preference. A2, K2, vertical, whatever feels right.

Muzzle Device thread pitch has to match your barrel. 1/2x28 for 5.56, 5/8x24 for .308.

Accessories

Optic, light, sling, backup sights, magazines. The builder has slots for all of these. The optic category alone has 1,586+ rifle scopes and 3,153+ mounts in the catalog.

Price Comparison from 30 Retailers

This is probably the feature that saves you the most money. The same BCM BCG can be $189 at one store and $169 at another. Multiply that across 10-15 parts in a full build and you're looking at real money left on the table.

GunPartPicker pulls pricing from 30 retailers and shows them side by side for every product. You see the price, whether it's in stock, and where to buy it. One page, no tab juggling.

The build page keeps a running total. Swap a barrel, the total recalculates. Try a different trigger, instant update. Makes it easy to play with different builds and see exactly what each choice costs.

Compatibility Checking

PCPartPicker won't let you put an AMD CPU on an Intel motherboard. GunPartPicker does the same thing for AR components.

Critical checks catch things that will actually cause a malfunction:

• Caliber mismatch (a .308 bolt in a 5.56 upper won't chamber)
• Platform mismatch (an AR10 upper physically won't fit an AR15 lower)

Warning checks flag things that might cause problems:

• Gas system length vs. barrel length (carbine gas on an 18" barrel runs over-gassed)
• Thread pitch mismatch (1/2x28 muzzle device on a 5/8x24 barrel won't thread on)
• Mounting interface conflicts (some handguards need specific barrel nuts)

The system warns you but doesn't block you. Sometimes you know what you're doing. Running a .300 BLK upper on a 5.56 lower? Totally fine, the lower is caliber-agnostic. The warnings catch genuine mistakes without gatekeeping experienced builders.

Shareable Build Links

Your build state lives in the URL. Every component, every slot, encoded right in the link. Copy it, text it to a buddy, post it on Reddit, save it in your notes. Whoever clicks it sees your exact build with current pricing.

No more typing out parts lists in forum posts. No more "here's what I'm thinking" walls of text. Just drop the link and people can see exactly what you've got. They can even fork it and make their own version.

Builds save to your browser automatically. Log in and they sync across devices. Close the tab, come back next week, your build is still there.

Sample Builds

Here are three starting points. Each one uses parts from the GunPartPicker catalog so you can jump in and start swapping.

Budget Build ($600-800)

PSA or Aero lower, Aero upper, mid-length 16" barrel, standard BCG and charging handle. Throw a Sig Romeo 5 on top and a sling. Runs reliably, gives you room to upgrade later.

Mid-Range ($1,200-1,500)

BCM or Aero upper with a quality barrel, Geissele or LaRue trigger, Radian charging handle, Holosun or Sig optic. The "buy once cry once" tier. This setup will run 20,000+ rounds without thinking about it.

Full Send ($2,000+)

KAC, LMT, or Daniel Defense upper. Geissele trigger. Aimpoint or EOTech. SureFire light. Every part chosen on purpose. Not a flex build. Just "this is my one rifle and I want it done right."

The Catalog by the Numbers

This isn't a small database. Here's what GunPartPicker currently tracks:

The top categories by volume: upper receivers (3,200+), optic mounts (3,100+), handguards (1,800+), rifle scopes (1,500+), and lower receivers (1,300+). The catalog covers everything from gas tubes to cleaning kits.

Why This Took So Long to Build

PC parts have standardized sockets, form factors, and a handful of big retailers. Firearms are different.

Parts are sold across dozens of small, specialized retailers. Aggregating prices means tracking inventory from 30+ stores, each with their own product feeds and stock systems.

Compatibility rules have exceptions. Caliber families, gas system lengths, thread pitches, rail interfaces, platform generations. The rules aren't as clean as "this CPU socket fits this motherboard." A .300 BLK runs on a 5.56 bolt but not a 5.56 barrel. An AR10 lower from one manufacturer might not mate with an AR10 upper from another due to DPMS vs. SR-25 pattern differences.

The product space is massive. 500+ brands. 50+ categories. Hundreds of barrel manufacturers alone, each with dozens of SKUs across different lengths, profiles, gas systems, and calibers. Getting that data structured, categorized, and searchable is a real engineering problem.

GunPartPicker solved all of this so you don't have to think about it.

Start Building

The tool is free, works on your phone, and you don't need an account. We're adding products and retailers constantly. 30,000+ parts and counting.

If you've been waiting for a PCPartPicker for guns, stop waiting.