Getting Started

1. What Is Ammunition Reloading?

Reloading (also called handloading) is the process of assembling firearm cartridges by hand — combining a case, primer, powder charge, and bullet into a finished round. Reloaders typically use a reloading press, dies, powder scale, and various other tools to produce ammunition at home or in a dedicated reloading room.

Why do people reload?

• Cost savings — Once equipment is paid off, the cost per round is typically 30–60 % lower than factory ammunition for centerfire calibers.
• Accuracy & consistency — Handloads can be tuned to a specific rifle's chamber and barrel twist, often producing tighter groups than off-the-shelf ammunition.
• Availability — During shortages, reloaders with an existing component inventory can continue training when store shelves are empty.
• Obsolete calibers — Some cartridges are no longer commercially loaded. Reloading is the only practical way to shoot older firearms chambered in them.
• Wildcat cartridges — Reloading allows shooters to experiment with non-standard cartridges that are never produced commercially.

The four components of a cartridge

• Case — Usually brass (sometimes steel or aluminum). Holds all the other components and expands on firing to seal the chamber.
• Primer — A small percussion-sensitive cup seated in the case head. When struck by the firing pin it ignites the powder charge.
• Powder — Propellant that generates gas to push the bullet down the barrel. Different powders burn at different rates (burn rate tables are a key resource).
• Bullet — The projectile. Bullets vary by weight (grains), construction (FMJ, HP, BTHP, etc.), and ballistic coefficient (BC).

2. Who Is OpenCartridge For?

OpenCartridge is built for a wide range of firearm enthusiasts:

• Beginners curious about reloading who want to research cartridges and see what loads other people are running before investing in equipment.
• Active reloaders who want to share their own proven loads, compare notes with the community, and discover new powder and bullet combinations.
• Competitive shooters (PRS, F-Class, IDPA, 3-Gun) hunting for the most accurate or softest-shooting load for their specific rifle.
• Long-range hunters interested in external ballistics — how a specific bullet will behave at 500, 700, or 1,000 yards.
• Collectors & historians who want dimensional specs and lineage data for vintage or obsolete cartridges.
• Gunsmiths and dealers who need quick reference data on cartridge dimensions and primer types.

3. Understanding Cartridge Specifications

Each cartridge page shows the full SAAMI-standard dimensional data. Here's what each field means:

Classification

• Platform — Rifle, Pistol, Shotgun, or Rimfire. Describes the firearm type the cartridge is designed for.
• Manufacture type — Commercial (produced by major ammo companies), Military (issued to armed forces), or Wildcat (non-standard, not produced commercially).
• Case type — Describes the case geometry: Rimless Bottlenecked, Belted Rimless, Rebated Rim, Straight, etc. This affects compatibility with certain actions and magazines.
• Cartridge family — Many cartridges are derived from a common parent case. For example, the 7mm-08, .243 Win, and .308 Win all share the same basic case.

Dimensions — all in inches

• Bullet diameter — The actual diameter of the bullet (and bore). This is what determines caliber. E.g., .308 Win uses a 0.308" bullet.
• Case length — Length of the cartridge case without the bullet seated. Critical for safe chambering.
• Total length (OAL) — Overall cartridge length with bullet seated. Must fit within the magazine box.
• Neck diameter — The diameter of the case mouth area that grips the bullet.
• Shoulder diameter — The widest part of the tapered section above the body. Affects headspace.
• Base diameter — Diameter at the base of the case body.
• Rim diameter — The flange at the case head used for extraction. Rimless cases have a rim slightly smaller than the base.

Other fields

• Primer — Small Rifle, Large Rifle, Small Pistol, Large Pistol, Magnum variants, Berdan, etc.
• Year introduced — When the cartridge was first commercially produced or standardized.
• Designer — The individual, company, or military branch credited with developing the cartridge.
• Parent case(s) — The cartridge(s) this design was derived from, typically through necking up/down or reforming.

4. How to Read Load Data

Community load submissions on OpenCartridge contain the following fields. Understanding each one helps you evaluate whether a load is appropriate for your components and firearm.

• Bullet weight (gr) — Heavier bullets are generally slower but retain energy better at distance. Common choices for .308 Win: 150gr (general purpose), 168gr (match), 175gr (long-range).
• Bullet brand & type — Match-grade bullets (Sierra MatchKing, Berger Hybrid) vs. hunting bullets (Nosler Partition, Federal Trophy Bonded) differ significantly in design intent.
• Ballistic coefficient (BC) — A dimensionless number expressing how well a bullet resists drag. Higher = less wind drift and less drop at distance. G1 and G7 are the most common drag models.
• Powder name & brand — The propellant used. Burn rate matters — fast powders suit pistols and small rifle cases; slow-burning powders are used in large-capacity magnum cases.
• Powder charge (gr) — The weight of powder in the case. This is the most safety-critical field. Never exceed published maximum loads from a reloading manual.
• Muzzle velocity (fps) — Measured at the muzzle with a chronograph. Affected by barrel length, temperature, altitude, and seating depth.
• Barrel length (in) — Longer barrels extract more velocity from slow-burning powders.
• Cartridge OAL (in) — The overall length the cartridge was assembled to. Must fit the magazine and not jam into the rifling, unless intentionally "touching the lands."
• Primer type — The specific primer brand and type used. Primers affect ignition consistency; Federal 210M Gold Medal Match primers, for example, are popular for precision rifle.
• Pressure (PSI/CUP) — If measured, this tells you how close the load is to the SAAMI pressure limit. Treat max-pressure loads with caution.
• ⚠ Max Load badge — User-marked loads at or near maximum published powder charge. Always work up to max loads starting 10 % below and watching for pressure signs.

Pressure signs to watch for

• Flattened or cratered primers
• Case head expansion (measure with a micrometer)
• Difficult bolt lift
• Sticky extraction
• Ejector marks on the case head

If you see any of these signs, stop immediately and reduce the powder charge.

5. Features Overview

6. Quick-Start Guide

New here? Here's the fastest way to get value out of OpenCartridge in under 5 minutes:

1. Search for your caliber. Type your cartridge name (e.g., "6.5 Creedmoor", "9mm Luger", ".30-06") into the search bar on the home page.
2. Review the spec card. The left panel of the cartridge page shows all dimensional data — bullet diameter, case length, primer type, and family. Use this to verify compatibility with your dies and brass.
3. Browse the Load Data tab. See what powders and bullet weights the community is using. Use the filter panel to narrow down by bullet type or narrow a muzzle velocity window. Look for loads with multiple upvotes — those are community-verified.
4. Check community velocity stats. The stats bar above the load list shows the average, min, and max muzzle velocity submitted for this cartridge — an instant sanity check against the load you're considering.
5. Save loads you want to try. Click the bookmark icon on any load card to save it to your personal Saved Loads page.
6. Submit your own load. After running loads through a chronograph, submit the data back to the community. Click Submit Load on any cartridge page. Your data helps other reloaders.
7. (Pro) Run the ballistics calculator. Enter your bullet weight, BC, muzzle velocity, and zero distance to get a full trajectory table and wind drift chart. Open the calculator.

7. Tips for Getting the Most Out of OpenCartridge

When researching a new load

• Filter loads to your exact bullet weight to see what charges other reloaders are using for that specific component.
• Sort by most recent to find loads using newer powders and components that may not be in older reloading manuals.
• Check the cartridge discussion tab — often other users mention quirks like pressure issues with certain powders or case brands that work better.
• Use the powder hub page (linked from any load card) to see how a specific powder performs across all calibers — useful for sizing up a new-to-you powder.

When submitting a load

• Include your barrel length — velocity is meaningless without it. A 24" barrel gives very different numbers than a 16" barrel with the same powder charge.
• Include your primer brand and type. Small details like Federal 210M vs. CCI 200 affect ignition pressure curves.
• Chronograph at least 5 shots and submit the average, not a single extreme reading.
• Mark a load as Max Load if it's at or near the published maximum. This warns other reloaders to work up carefully.
• Upload a photo of your target or case heads — visual evidence builds community trust in your data.

For long-range shooters (Pro)

• Input your actual altitude and temperature — density altitude significantly affects ballistics above 3,000 ft.
• Use the shot angle slider when hunting in mountainous terrain. The Rifleman's Rule adjustment can mean 1–2 MOA at steep angles.
• Generate a DOPE card for each environmentally-distinct hunt location — sea level coastal hunting vs. high-altitude mountain hunting requires different elevation holds.
• Cross-check your calculator output against real-world andchronograph data. No external ballistics calculator replaces a known-drops data set from your actual rifle and load.

Comparing cartridges

• Use the compare tool (checkboxes on each cartridge card) to put two or more cartridges side-by-side before committing to a new chambering.
• Browse the family hub for a cartridge to find parent and sibling cases — useful when sourcing brass or understanding what dies might work for forming.

8. Safety Disclaimer & Automated Charge Warnings

Reloading is inherently dangerous if not done correctly. Excessive pressure can cause catastrophic firearm failure resulting in serious injury or death. OpenCartridge is a community reference tool, not a professionally edited reloading manual.

• Always verify against a published manual — Hodgdon Annual, Lyman Reloading Handbook, Sierra, Hornady, Nosler, or Speer. These are tested in controlled conditions with calibrated equipment.
• Never exceed SAAMI maximum loads — just because someone on the internet is running a hot load doesn't mean your components, brass headstamp, or rifle can handle it.
• Work up incrementally — Start 10 % below maximum and add 0.5gr at a time while watching for pressure signs.
• Components affect pressure — Brass manufacturer, case capacity, primer brand, and seating depth all affect chamber pressure. A load developed with one brand of brass may be unsafe in another.
• Keep records — Log every load you develop including the date, lot numbers of components, and measured velocity. This lets you systematically troubleshoot problems.
• Wear eye protection — Always, at the range and at the loading bench.

How Automated Charge Warnings Work

When a new load is submitted, OpenCartridge automatically analyzes it against every other public load in the same cartridge and bullet weight group. If the powder charge is a statistical outlier compared to the rest of the community data, the load is tagged with an ⚠ UNUSUAL CHARGE warning badge. There are two possible warnings:

• High charge — the powder charge is significantly above the typical range for that cartridge and bullet weight. This may indicate a data-entry error, an unsafe load, or a specialized use case. Either way, it warrants careful scrutiny before use.
• Low charge — the powder charge is significantly below the typical range. Unusually light charges can cause squib loads — rounds where the bullet does not exit the barrel, which can cause catastrophic damage if followed by a second round.

How the calculation works

The algorithm requires at least 4 public loads in the same group before it will flag anything — sparse data is not enough to call something an outlier. Once there are 4 or more loads, it calculates the mean (average) and standard deviation of the powder charges in the group. Any load whose charge is more than 3 standard deviations from the mean — what statisticians call a z-score beyond ±3.0 — is flagged as an outlier. A 3σ threshold means roughly 99.7 % of normally-distributed data falls within the safe zone; only genuinely extreme values get flagged.

Flags are recalculated every time a new load is added to the group, so as more community data arrives the thresholds adjust automatically. A load that was previously flagged can have its warning removed if new submissions shift the typical range.

Our liability

OpenCartridge, its contributors, and its operators are not liable for any injury, damage, or loss resulting from the use of data found on this site, regardless of whether a safety warning was or was not displayed on a given load. The automated outlier detection is a best-effort community safety tool, not a substitute for professional guidance. User-submitted load data has not been independently verified or pressure-tested. You are solely responsible for every round you load and fire. Use this site at your own risk and always consult a current printed reloading manual.

9. Frequently Asked Questions