Two boxes of the same cartridge, same bullet weight, same manufacturer, can shoot to different points of impact and behave completely differently on game. The number on the box is the smallest part of what you are buying.
This guide covers what actually distinguishes rifle ammunition — bullet construction, weight and twist rate, ballistic coefficient — and how to pick the right load for hunting, competition, or practice.
Reading a box
A typical label gives you four things:
- Cartridge — must match your chamber exactly. “.308 Winchester” and “7.62×51” are close relatives but not identical; “.223 Remington” and “5.56 NATO” differ in pressure and chamber spec, and the direction you substitute matters.
- Bullet weight in grains. Heavier is not automatically better — see twist rate below.
- Bullet type — the abbreviation that tells you how it is built and what it will do on impact.
- Velocity, usually a test-barrel figure. Your rifle will differ, often by a lot, depending on barrel length.
Never fire a cartridge your barrel is not marked for. If the stamp and the box do not agree, stop and check.
Bullet construction is the real variable
This determines what happens after the bullet arrives, which is the entire point on game.
Cup and core
A lead core inside a copper jacket — the traditional, affordable construction. Expands readily and kills well at moderate impact velocities. At very high velocity or on heavy bone it can come apart and under-penetrate.
Bonded
The core is chemically bonded to the jacket so the bullet holds together while expanding. Retains far more weight, penetrates deeper, and performs across a wider velocity range. The sensible default for larger game or where shots may be close and fast.
Monolithic (all copper)
Solid copper or gilding metal, no lead. Very high weight retention and deep, straight penetration. Also the answer where lead-free ammunition is required — some states and public lands mandate it. They are longer than a lead bullet of the same weight, which makes twist rate more important.
Match and open-tip
Built for accuracy and consistency, not terminal performance. The hollow tip on an OTM is a manufacturing artifact of the jacket-forming process, not an expansion feature. Superb on paper and steel; expansion on game is inconsistent and unpredictable, which is why they are not a hunting bullet.
Polymer tip
A plastic tip that resists deformation in the magazine, improves the ballistic coefficient, and drives back on impact to initiate expansion. Common on both hunting and match bullets, over various core designs.
FMJ
Full metal jacket. Cheap practice ammunition. It does not reliably expand, which makes it a poor and in many places illegal choice for hunting big game.
Bullet weight and twist rate
This is the specification most buyers ignore and the one that decides whether a load will shoot.
Your barrel’s twist rate — expressed as one turn in so many inches, like 1:8 — determines how fast the bullet spins, and therefore how long a bullet it can stabilize. Longer, heavier bullets need faster twist. A slow-twist barrel fed heavy bullets will produce erratic groups or visibly oval holes in paper, and no amount of load development fixes it.
Check your barrel’s twist before buying a case of heavy match ammunition. It is usually marked, in the manual, or on the maker’s site. Remember that monolithic copper bullets are longer than lead bullets of the same weight, so they demand more twist than the grain figure suggests.
Ballistic coefficient
BC is a measure of how well a bullet resists drag. Higher BC means less drop, less wind drift, and more retained energy downrange.
It matters enormously past about 400 yards and very little inside 200. A high-BC match bullet is wasted on a 100-yard whitetail rifle, and chasing BC at the expense of a bullet that actually performs on game is a common mistake.
Wind is where BC earns its keep — it is the variable you can read least accurately, so reducing its effect helps more than a flatter trajectory. For more, see our comparison of the best long range rifle calibers.
Match the load to the job
| Use | What to buy |
|---|---|
| Deer and similar game | Bonded or quality cup-and-core, mid-weight for the cartridge |
| Elk and large game | Bonded or monolithic, heavier for caliber, weight retention over BC |
| Long-range hunting | High-BC bonded or tipped hunting bullet — not a match bullet |
| Varmints | Light, rapidly expanding bullets |
| Target and competition | Match or OTM, highest BC your twist will stabilize |
| Practice and plinking | FMJ or budget soft point in the same weight as your hunting load |
| Lead-free areas | Monolithic copper — verify your twist rate |
A useful trick: practice with the cheapest ammunition in the same bullet weight as your hunting load. It will not group identically, but recoil and point of impact stay close enough that your practice transfers.
Brass, steel, and case material
Brass is the standard, seals the chamber well, and is reusable if you reload. Steel case is cheaper and works fine in rifles designed for it, but it is not reloadable, can be harder on extractors over high round counts, and some ranges ban it because it will not separate magnetically from brass scrap.
If you have any intention of handloading, buy brass-cased ammunition and keep the brass. It is the most expensive component and the only reusable one.
Your rifle has an opinion
Rifles are individual. Two identical rifles off the same line can prefer different loads, and the only way to know is to test.
Buy one box each of three or four candidate loads, shoot them from a rest at the same session, and compare group size and point of impact. Then buy the winner in quantity — from the same lot if you can, because lot-to-lot variation is real, and a load you spent a season developing can shift when you buy new stock.
Record the lot number with your dope. When you buy new ammunition, re-confirm zero before you hunt with it.
Storage, and why heat matters
Ammunition stored cool and dry lasts decades. What degrades it is heat and temperature cycling — and a garage, a shed, or a parked vehicle through any hot summer is exactly that environment. That is true across the Southwest and most of the South; here in Arizona it is simply unavoidable for five months a year.
Heat also raises chamber pressure. A load worked up in cool weather can behave differently on a very hot day, which is worth knowing if you develop handloads in winter and hunt in September. Store ammunition inside the conditioned part of the house, and do not leave a hunting supply in the truck all season.
Common questions
Can I shoot 5.56 in a .223 rifle?
Not safely as a rule. 5.56 is loaded to higher pressure with a different chamber spec. A .223-marked chamber should get .223; a 5.56 or hybrid chamber will generally handle both. Check your barrel marking, and if in doubt ask us or the manufacturer.
Is match ammunition better for hunting?
No. It is built for consistency, not terminal performance, and its expansion on game is unpredictable. Use a hunting bullet for hunting.
Does heavier hit harder?
Heavier bullets retain energy better and penetrate deeper, but only if your twist rate stabilizes them. An unstable heavy bullet is worse than a stable lighter one in every respect.
Does ammunition ship to my door?
Yes, where local law allows — ammunition is not a serialized firearm. Some states and cities restrict shipments, so check the rules where you live.
Where to start
Check your twist rate, choose a bullet built for what you are actually shooting, test three or four loads in your rifle, then buy the winner in quantity and record the lot.
Browse rifle ammunition and the wider ammunition selection. Still choosing a cartridge? See .308 vs 6.5 Creedmoor or, for AR platforms, our 6mm ARC comparison. Want ammunition tuned to your rifle specifically? Start with reloading.