Rifle Ammunition — Calibers, Bullet Types & Choosing the Right Load
Rifle ammunition selection comes down to three variables: caliber, bullet construction, and intended use. Get all three right and your ammunition works for its purpose. Miss any one and you are either overpaying, underperforming, or running ammunition that creates problems at the range.
Caliber selection is determined primarily by what rifle you own and what you're doing with it. 5.56 NATO and .223 Remington are the dominant AR-15 calibers — the widest availability, lowest cost per round, and the most thoroughly tested terminal performance data of any rifle cartridge category. .308 Winchester is the standard for bolt-action hunting and precision shooting at distances beyond 300 yards. 6.5 Creedmoor has largely displaced .308 for precision competition due to its superior ballistic coefficient, flatter trajectory, and lower recoil at comparable distances. 7.62x39mm is the AK platform standard — effective at close to medium range from short barrels. For a detailed 5.56 breakdown by load type, see our best 5.56 ammo guide.
Bullet construction determines terminal performance. Full metal jacket (FMJ) bullets do not expand and are the standard for range training — inexpensive, feed reliably in semi-automatics, and legal at all ranges that allow rifle calibers. Hollow point and soft point bullets expand on impact, increasing wound channel diameter and reducing over-penetration — appropriate for hunting and some defensive applications depending on caliber. Open Tip Match (OTM) bullets are precision projectiles that happen to have an open tip for manufacturing reasons — they are not hollow points in the defensive sense but do exhibit terminal performance similar to soft points on impact. For hunting, use bullets designed for controlled expansion appropriate to the game species and distance.
Steel vs brass case is a common question. Brass-cased ammunition is reloadable, produces slightly better accuracy, and is accepted at all ranges. Steel-cased ammunition (Wolf, Tula) costs less per round but many indoor ranges ban it due to fire risk from bimetal jackets, and it cannot be reloaded. Most modern AR-15s run steel-cased ammo reliably, though extraction is slightly rougher and accuracy is typically 1-2 MOA less than brass equivalents.
For state-specific ammunition restrictions, see our ammo and magazine laws guide. For 5.56 vs .223 chamber compatibility, see our .223 vs 5.56 comparison.
Rifle Ammunition Frequently Asked Questions
What is the difference between M193 and M855 5.56 ammunition?
M193 is a 55-grain full metal jacket bullet traveling approximately 3,165 fps from a 20-inch barrel. At velocities above 2,700 fps — which a 16-inch barrel achieves at typical defensive distances — M193 fragments dramatically on impact, making it more effective than most buyers expect as a defensive round. M855 is a 62-grain bullet with a 7-grain steel penetrator, traveling approximately 3,020 fps. The steel penetrator improves barrier penetration and wind resistance at extended range but tends to yaw through soft tissue without fragmenting as reliably as M193 at close range. Many indoor ranges ban M855 because the steel penetrator damages backstops. For range training, M193 is the better choice. For barrier penetration and extended range, M855 is more effective. For home defense, dedicated defensive loads outperform both. See our complete 5.56 ammo guide for full details.
Is 6.5 Creedmoor better than .308 Winchester?
For precision shooting past 300 yards and competition, yes. The 6.5 Creedmoor's higher ballistic coefficient means it retains velocity and energy better at distance while drifting less in crosswinds. At ranges under 300 yards on deer-sized game, the terminal performance difference is negligible. The primary argument for .308 is ammunition availability — .308 is the most widely stocked rifle cartridge in the country and available everywhere. 6.5 Creedmoor has excellent distribution but cannot match .308's universal availability. For hunters who shoot beyond 300 yards or compete in precision rifle matches, 6.5 Creedmoor is the better tool. For hunters who primarily shoot under 300 yards in areas where resupply availability matters, .308 is the more practical choice.
Is steel-cased ammo safe to use in my AR-15?
Yes, with caveats. Steel-cased ammunition (Wolf, Tula, Bear) runs reliably in most AR-15s, though extraction is slightly rougher than brass-cased ammo and accuracy is typically 1-2 MOA less. The main practical limitations: many indoor ranges ban steel-cased ammo due to fire risk from bimetal (steel/copper) jackets hitting steel backstops; the cases cannot be reloaded; and some rifles — particularly tightly chambered match-grade barrels — may have extraction issues. For high-volume training where cost per round is the primary concern and you shoot at an outdoor range, steel-cased is a legitimate choice. For precision shooting, defense, or indoor ranges, use brass-cased.
What rifle ammunition is best for home defense?
For AR-15 platform home defense in 5.56, use a purpose-built defensive load rather than military ball ammunition. Hornady V-MAX 55gr, Speer Gold Dot 75gr, and Federal Tactical Bonded 55gr are the three most widely validated 5.56 defensive loads. These expand or fragment reliably across a wider velocity range than standard FMJ, are designed to minimize over-penetration compared to non-expanding ammunition, and perform consistently through intermediate barriers. Function-test at least 50 rounds through your specific rifle before trusting any defensive load. For .308 defensive use in a bolt-action, Federal Fusion and Hornady American Whitetail soft points expand reliably and are appropriate for home defense in rural settings.