.40 Smith & Wesson Ammo Recommendations

.40 S&W AMMO RECOMMENDATIONS

9mm PCCs on the AR platform behave very differently depending on barrel length, magazine type, and how the gun is tuned, so ammo choice and setup matter for reliability and terminal performance.

This guide separates rifle‑length and pistol‑length PCCs and gives the practical starting loads and tuning checks you should run in your exact lower, mag, and barrel.

Rifle‑length PCCs (16″+ barrels)

• Training / Range: 165–180 gr FMJ — cheap, feeds reliably, great for high‑volume practice and function checks.

• Duty / Self‑Defense: 165 gr bonded/JHP or 180 gr JHP — common defensive choices (look at bonded Gold Dot / HST / Hornady options).

• Competition / Performance: 165 gr plated or match‑grade loads for reduced recoil and consistent splits; tune blowback/gas or buffer for consistency.

• Suppressed Use: 180 gr subsonic options perform best suppressed; chrono to verify subsonic speed in your barrel.

• Build notes: Carbine barrels usually push .40 S&W faster than pistols — expect altered terminal behavior vs handgun loads. Use Glock‑pattern (.40) magazines or AR‑specific .40 mag options and tune buffer/spring or gas to the load.

Pistol‑length PCCs (Less than 16” AR‑pistol barrels)

• Training / Function: 165–180 gr FMJ for feeding/cycling validation — short barrels can be picky, start here.

• Carry / Home‑Defense: 165 gr JHPs proven to expand from short barrels; prefer bonded versions for barrier performance.

• Suppressed Pistol PCCs: 180 gr subsonic bonded/monolithic or purpose‑built subsonic JHPs — heavy bullets retain energy and stay quiet suppressed.

• Reliability tips: Short barrels and lower gas impulse often require buffer/spring tuning or an adjustable gas/delayed‑blowback setup. Run extended function tests (50–200 rounds) after changes.

• Feeding & mags: Magazine choice and follower type are critical — test the exact magazines you’ll use for carry or competition.

Tips for Best Results

• Chronograph & function‑test everything in the exact AR lower, magazine, and barrel length you’ll use.

• Start with one FMJ and one defensive JHP and validate feeding, extraction, and accuracy.

• Tune buffer/spring or gas system for short‑barrel and light‑load reliability — don’t assume a generic kit will run everything.

• Suppressed builds: prefer 147 gr subsonic or purpose‑built suppressed loads and test suppressed and unsuppressed cycling.

• Mags matter: use the magazine type your build is designed for and test +/- different followers if you see issues. ABC PCC lowers use Glock style magazines.