Build planner and price comparison for gun parts and ammo
About GunPartPicker
Why GunPartPicker exists
Planning a build used to mean a spreadsheet, twenty browser tabs and a guess at whether the parts would fit together. GunPartPicker replaces that with one page: pick parts by slot, see every retailer's price for each one, and get a warning the moment two parts do not match.
The idea comes from PCPartPicker. It launched in 2020 as an AR-15 builder and has grown into the whole AR platform (AR-15, AR-10 and AR-9), a Glock builder, and live ammo prices per round across 55 calibers. Prices and stock refresh from nearly 30 retailer feeds.
Whether it is your first AR-15, a clone build, a lightweight rig, a competition Glock or a case of 9mm, the goal is the same: clarity on what fits, and the best price on every line.
What you can build
AR-15, AR-10 and AR-9
Barrels, receivers, BCGs, handguards, triggers, optics and 40+ more categories. Caliber and platform are checked as you add parts.
Open the AR BuilderGlock
Slides, barrels, frames, triggers, sights, optic plates, magazines and completion kits for a slot by slot pistol build.
Open the Glock BuilderAmmo
Live price per round across 55 calibers, one hub per caliber, plus the Ammo Finder to compare by grain, brand and price.
See ammo pricesHow it works
- 1
Pick a builder
AR Builder for AR-15, AR-10 and AR-9. Glock Builder for pistols.
- 2
Add parts
Search or browse by category and brand. One product per slot, swap any time.
- 3
Watch the compatibility checks
Caliber, platform, gas length, thread pitch and mounting interface are checked as you go. Warnings never block you.
- 4
Compare prices
Each part shows every retailer that carries it, sorted by price, with stock status. The build total updates live.
- 5
Buy where it is cheapest
Every Buy button opens the retailer's own product page. Save the build first and share it with one link.
Compatibility checks
Every part you add is checked against the build so far. The checks are ranked, and none of them stop you from adding a part.
- Critical: caliber against the upper receiver, and AR-15 versus AR-10 platform against the lower receiver.
- Warning: gas system length between barrel and gas tube, and thread pitch between barrel and muzzle device.
- Fit: mounting interface (M-LOK, Picatinny, KeyMod) and optic tube size against the mount.
Builds, guides and tools
Completed builds is the community feed: real parts lists with today's prices, filterable by part, brand, caliber and budget. Post yours, or borrow one as a starting point.
Guides cover buyer's guides by category, film and military clone builds, Glock upgrades and gun laws by state, with product cards priced from the live catalog.
Gun Tools answer one question each from live data: the AR build cost calculator, gun travel checker, muzzle thread checker, FRT and binary trigger picker, Glock red dot fit, twist rate, buffer weight and barrel length.
What GunPartPicker is not
The site earns a commission from some retailers when you buy through a link. That never changes your price, and it never changes which retailer is listed first: the cheapest in stock price wins. Read the affiliate disclosure.
Industry data
Gun Industry Insights is our quarterly report on what builders are choosing and paying: the most popular parts by slot, brand build share, the AR-15 Build Cost Index and an Ammo Price Index across 55 calibers, free to cite with attribution. Brands and retailers can advertise with us. Questions go to contact.
FAQ
Frequently asked questions
Is GunPartPicker a store?
- No. GunPartPicker is a build planner and price comparison. We do not sell, stock or ship anything. Every Buy button goes to a third party retailer, and the purchase happens there. Some of those links are affiliate links, which is how the site stays free.
Does the AR Builder support AR-10 and AR-9 builds?
- Yes. The AR Builder covers AR-15, AR-10 and AR-9 builds. Platform is anchored on the lower receiver and caliber on the upper, so AR-15 and AR-10 parts are checked separately and cannot be mixed by accident.
Can I plan a Glock build?
- Yes. The Glock Builder plans a pistol slot by slot: slide, barrel, frame, trigger, sights, optic plate, magazine and more, with the same live prices, saved builds and share links as the AR Builder.
How do the ammo prices work?
- Every caliber has its own hub with live price per round, in stock status and the retailer count, refreshed from retailer feeds. The Ammo Finder compares ammo by caliber, grain, brand and price per round and lets you save a list.
Do I need an account?
- No. Builds save on your device as you go. A free account keeps them across your phone and desktop and gives each build a page you can share with one link.
Is GunPartPicker free?
- Yes. Building, comparing, saving and sharing are free. The site earns a commission from some retailers when you buy through a link, which never changes the price you pay.
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