Stock the ammo that matches how you shoot. Supersonic for unsuppressed range work, subsonic if you run a suppressor. Test subsonic cycling in your exact setup before buying deep, and keep 300 BLK physically separate from 5.56.
300 Blackout lets an AR-15 fire a .30-caliber bullet using the same bolt and magazines. It was designed to work well from short barrels and to run quietly with heavy subsonic loads through a suppressor. That flexibility is why stocking it is a little more complicated than stocking 5.56: most owners need two kinds of ammo.
Supersonic vs. subsonic
| Type | Typical bullets | Best for |
|---|---|---|
| Supersonic | Lighter, commonly about 110 to 125 grains | Unsuppressed range work, general use |
| Subsonic | Heavy, commonly about 200 to 220 grains | Suppressed shooting |
Subsonic loads stay below the speed of sound, so there's no supersonic crack, and through a suppressor they're very quiet. They also have much less energy and a steep trajectory. Our subsonic vs supersonic guide explains the physics.
How to split your budget
- No suppressor: mostly supersonic. Subsonic has few advantages without a can.
- Suppressor owner: mostly subsonic, with some supersonic for longer-range work.
- Still deciding: small quantities of both until you know how you shoot.
Test subsonic cycling first
Before buying subsonic by the case, confirm it cycles your rifle. Heavy subsonic loads generate less gas, and some rifles only run them reliably with a suppressor attached. Buy a box or two, test with your actual configuration, and only then buy in bulk.
Magtech .300 Blackout 200gr Subsonic FMJ
A heavy subsonic range load. A good test box before committing to a case.
Subsonic ammo category
Every subsonic load in stock, including other 300 BLK options.
Rifle ammo category
Browse supersonic 300 Blackout loads and other rifle calibers.
How much to stock
300 Blackout costs more per round than 5.56 and is usually shot at a slower pace, especially suppressed. A few hundred rounds of your main type covers many owners for months. If you shoot suppressed every week, a case of subsonic is a sensible unit once you've confirmed it runs. Our 1,000-round baseline helps size your number.
Zero for your main load
Buying for a suppressor host
If your 300 Blackout is mainly a suppressor host, prioritize consistency over the lowest price. Suppressed shooters often notice differences between loads: some are quieter, some produce more gas back toward the shooter, and some cycle more reliably. Try two or three subsonic loads in small quantities, note how each behaves with your can attached, and pick one to buy in quantity.
Keep a small supply of supersonic ammo too, even if you mostly shoot suppressed. It's useful for longer shots, for testing that the rifle runs without a suppressor, and for times you shoot with the can off. Our guide to buying ammo online covers shipping rules and FFL-free delivery basics for ammunition.
Finally, remember that 300 Blackout supply tends to be less steady than 5.56. When you find a load that runs well, buying a bit deeper than usual can save you from switching loads and re-zeroing during a dry spell.
Keep receipts or order records with the lot numbers, too. If a batch ever gives you trouble, you'll know exactly which rounds to set aside and which lot to avoid on your next order. That small habit makes troubleshooting much faster.
Supersonic and subsonic loads hit in very different places, especially past short range. Zero your optic for the load you shoot most, then confirm and note where the other one lands. Many owners write the holdover on a card in the case so there's no guessing on the next trip.
Key takeaways
- Most 300 BLK owners need both supersonic and subsonic ammo.
- Buy mostly subsonic only if you shoot suppressed.
- Test subsonic cycling before buying a case.
- Keep 300 BLK physically separate from 5.56 at all times.
Product links go to Ammunition Depot through affiliate links; we may earn a commission. Stock and pricing change often, so check the live listing.
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FAQ
Is 300 Blackout cheaper than 5.56?
No. It generally costs more per round.
Will subsonic ammo cycle my AR?
Not always. Some rifles need a suppressor attached. Test with your setup before buying in bulk.
Do 300 BLK and 5.56 use the same magazines?
Generally yes, which is why labeling magazines matters.
Should I buy supersonic or subsonic?
Supersonic without a suppressor, subsonic with one, and small amounts of both while you decide.