Reliable .357 Magnum reloading data can be found in established publisher manuals from Lyman, Hornady, Speer, and the Hodgdon Reloading Data Center. Published data normally includes the specific bullet design, starting powder charge, maximum published powder charge, expected velocity, and cartridge overall length. Common bullet weights covered by published .357 Magnum load data range from 110-grain lightweight defense hollow points up to 180-grain heavy hunting projectiles. Results naturally vary between sources due to differences in the exact bullet profile, powder lot, brass, primer type, vented test barrel length, and atmospheric test conditions.
.357 Magnum Reloading Data
| Bullet | Bullet Weight | Powder | Published Starting Load | Published Maximum Load | Published Velocity | Pressure (Max) | Primer & Case | Cartridge Overall Length (COL) | Barrel Length / Firearm | Source |
| Hornady XTP | 125 grain | Hodgdon H110 | 21.0 gr | 22.0 gr | 1,966 fps | 41,400 CUP | Small Pistol Mag / Win | 1.590″ | 10.00″ / Universal | Hodgdon |
| Hornady XTP | 125 grain | Winchester 296 | 21.0 gr | 22.0 gr | 1,966 fps | 41,400 CUP | Small Pistol Mag / Win | 1.590″ | 10.00″ / Universal | Hodgdon |
| Speer GDHP | 135 grain | Accurate No. 9 | 12.8 gr | 14.3 gr | 1,418 fps | 34,212 PSI | Small Pistol / Starline | 1.575″ | 6.00″ / Revolver | Western Powders |
| Hornady XTP | 140 grain | Alliant 2400 | 13.0 gr | 14.8 gr | 1,372 fps | 34,100 PSI | Small Pistol / Speer | 1.575″ | 6.00″ / Universal | Alliant / Speer |
| Hornady XTP | 158 grain | Hodgdon H110 | 15.0 gr | 16.7 gr | 1,591 fps | 40,700 CUP | Small Pistol Mag / Win | 1.580″ | 10.00″ / Universal | Hodgdon |
| Cast LSWC | 158 grain | Winchester 231 | 3.4 gr | 5.0 gr | 1,109 fps | 23,900 CUP | Small Pistol Mag / Win | 1.610″ | 10.00″ / Universal | Hodgdon |
| Speer LSWC | 158 grain | Alliant Unique | 5.5 gr | 6.0 gr | 1,034 fps | Not Listed | Small Pistol / Speer | 1.580″ | 6.00″ / Universal | Alliant |
| Hornady XTP | 158 grain | Hodgdon Lil’ Gun | 16.0 gr | 18.0 gr | 1,577 fps | 25,800 CUP | Small Pistol Mag / Win | 1.580″ | 10.00″ / Universal | Hodgdon |
| Nosler Partition | 180 grain | Hodgdon Lil’ Gun | 13.0 gr | 15.0 gr | 1,422 fps | 40,000 CUP | Small Pistol Mag / Win | 1.575″ | 10.00″ / Universal | Hodgdon |
| Cast LFP | 180 grain | Accurate No. 9 | 10.8 gr | 12.0 gr | 1,326 fps | 34,600 PSI | Small Pistol / Starline | 1.580″ | 6.00″ / Revolver | Western Powders |
Understanding The .357 Magnum Reloading Data
To safely develop a .357 Magnum load recipe, reloaders must understand the specific variables documented in published load data charts:
- Starting load: The minimum safe powder charge. With slow-burning magnum powders (like H110 and W296), dropping below the starting load can cause dangerous squibs where the bullet becomes lodged in the barrel.
- Maximum published load: The maximum safe powder limit tested by the laboratory. Exceeding this risks catastrophic cylinder failure.
- Velocity: The bullet speed in feet per second (fps) measured at the muzzle during laboratory testing.
- Pressure: The SAAMI maximum average pressure limit for the .357 Magnum is currently 35,000 PSI (historically measured as roughly 45,000 CUP).
- Bullet weight: The mass of the 0.357-inch projectile in grains.
- Powder: The specific propellant. Fast-burning pistol powders are used for light target loads, while slow-burning magnum powders are required for full-power hunting loads.
- Barrel length: The laboratory test barrel length. Standard manuals frequently utilize 10-inch unvented barrels or 6-inch vented barrels that mimic a revolver’s cylinder gap.
- Firearm used for testing: Universal receiver test barrels or production revolvers.
- Test conditions: Altitude, humidity, and temperature variables during pressure testing.
- Cartridge overall length (COL): The total length of the loaded round. Revolver cylinder lengths strictly dictate COL; loading a bullet past the cylinder face will bind the firearm.
Different published sources produce varying results because they use brass with different internal volumes, differing primer brands, varying powder lots, and unvented versus vented test barrels.
.357 Magnum Bullet Weight Reloading Data
The .357 Magnum is incredibly versatile, supporting a massive spectrum of bullet weights for varying applications.
- 110 grain to 125 grain: The traditional self-defense and varmint weights. The 125-grain jacketed hollow point (JHP) is widely considered the gold standard for stopping power. These lightweight bullets are driven to blistering velocities, often exceeding 1,500 to 1,900 fps in test barrels, though they produce significant muzzle flash and blast.
- 140 grain: An excellent mid-weight compromise, offering slightly deeper penetration than the 125-grain while shooting flatter than the 158-grain.
- 158 grain: The original, quintessential standard weight for the cartridge. Copious data exists for 158-grain Lead Semi-Wadcutters (LSWC) and JHPs. These offer exceptional penetration, accuracy, and sight regulation in fixed-sight revolvers.
- 180 grain: Heavy hunting and metallic silhouette projectiles. Bullets like the 180-grain Nosler Partition or hard-cast wide flat nose (WFN) designs are utilized for deep penetration on deer and feral hogs.
Do not assume a 158-grain cast lead bullet utilizes the exact same powder charge as a 158-grain jacketed bullet. Lead bullets create less bore friction, which alters the pressure curve and frequently requires specific cast-bullet data.
.357 Magnum Powder Reloading Data
The .357 Magnum powder selection ranges from fast-burning target propellants to slow-burning magnum powders designed for heavy hunting loads.
| Powder | Bullet | Bullet Weight | Published Starting Load | Published Maximum Load | Published Velocity | Source |
| Hodgdon H110 | Hornady XTP | 125 grain | 21.0 gr | 22.0 gr | 1,966 fps | Hodgdon |
| Winchester 231 | Cast LSWC | 158 grain | 3.4 gr | 5.0 gr | 1,109 fps | Hodgdon |
| Alliant 2400 | Hornady XTP | 140 grain | 13.0 gr | 14.8 gr | 1,372 fps | Alliant |
| Accurate No. 9 | Speer GDHP | 135 grain | 12.8 gr | 14.3 gr | 1,418 fps | Western Powders |
| Hodgdon Lil’ Gun | Nosler Partition | 180 grain | 13.0 gr | 15.0 gr | 1,422 fps | Hodgdon |
Never reduce Hodgdon H110 or Winchester 296 powder charges by more than 3% below the published maximum. Undervaluing these specific ball powders causes erratic ignition, dangerous hang-fires, and severe pressure spikes.
.357 Magnum Bullet And Powder Combinations
The safety and consistency of .357 Magnum reloading data depend on precise component combinations.
- Primer choice: When utilizing dense, slow-burning spherical powders (like H110, W296, or Lil’ Gun), Small Pistol Magnum primers are strictly required to ensure complete, consistent powder ignition. If utilizing faster-burning extruded or flake powders (like Alliant 2400 or Unique), standard Small Pistol primers are sufficient.
- Bullet construction and bearing surface: A jacketed bullet requires a slightly heavier powder charge to overcome bore friction compared to a lubricated cast lead bullet of the exact same weight.
- Crimp: The .357 Magnum generates sharp recoil. A heavy, firm roll crimp into the bullet’s cannelure or crimp groove is absolutely mandatory. Without a heavy crimp, recoil will back unfired bullets out of their cases until they jam against the forcing cone. A heavy crimp also aids in building the necessary initial pressure to cleanly burn slow magnum powders.
- Forcing cone wear: Shooting copious amounts of lightweight (110-grain to 125-grain) bullets with maximum charges of slow-burning powders can cause accelerated “flame cutting” on the top strap and forcing cone of K-frame sized revolvers.
.357 Magnum Velocity From Published Data
Published .357 Magnum velocity figures vary dramatically based on the test equipment utilized by the laboratory.
| Bullet | Bullet Weight | Powder | Published Load | Muzzle Velocity | Barrel Length | Firearm | Source |
| Hornady XTP | 125 grain | H110 | 22.0 gr (Max) | 1,966 fps | 10.00″ | Universal Receiver | Hodgdon |
| Speer GDHP | 135 grain | Acc. No. 9 | 14.3 gr (Max) | 1,418 fps | 6.00″ | Vented Revolver | Western Powders |
| Hornady XTP | 158 grain | H110 | 16.7 gr (Max) | 1,591 fps | 10.00″ | Universal Receiver | Hodgdon |
It is crucial to distinguish between 10-inch unvented universal receiver barrels (which yield artificially high velocities) and vented test barrels (which mimic the cylinder gap of a real revolver). Do not present a 10-inch unvented laboratory velocity as achievable from an off-the-shelf 4-inch carry revolver.
.357 Magnum Reloading Data By Barrel Length
Barrel length heavily dictates the velocity a reloader will achieve in the .357 Magnum. While major publishers utilize 10-inch or 6-inch test barrels for handgun data, the cartridge is incredibly popular in lever-action rifles.
When firing a 158-grain maximum load of H110 from a 4-inch service revolver, shooters will typically record velocities around 1,250 to 1,300 fps. When that exact same load is fired from an 18-inch or 20-inch lever-action rifle (like a Marlin 1894), the lack of a cylinder gap and the extended barrel burn time pushes the velocity past 1,750 fps. Conversely, firing that load from a 2-inch snub-nose revolver will typically drop the velocity down into the 1,100 fps range. Reloaders must clearly identify their test firearm and barrel length when setting ballistic expectations.
.357 Magnum Energy And Ballistics
The .357 Magnum relies on high velocity to deliver devastating kinetic energy and deep penetration. Using verified manufacturer handgun data equivalents:
- 125-grain JHP (at 1,500 fps):
- Muzzle energy: ~624 ft-lbs
- 158-grain JHP (at 1,250 fps):
- Muzzle energy: ~548 ft-lbs
Fired from an 18-inch lever-action carbine, a 158-grain bullet traveling at 1,750 fps generates over 1,070 ft-lbs of muzzle energy, transforming the .357 Magnum into a highly effective 100-yard deer rifle cartridge.
Manufacturer Data vs Independent Testing
When researching a .357 Magnum load data chart, handloaders will encounter:
- Manufacturer-published reloading data: Officially pressure-tested in a laboratory to guarantee loads stay safely under the 35,000 PSI limit.
- Independent chronograph testing: Velocities recorded by handloaders using commercial chronographs over real revolvers or lever-action rifles. This verifies speed but cannot measure internal chamber pressure.
- User-submitted load reports: Internet forum recipes that often push past published maximums, referencing older, hotter manuals from the 1970s.
Independently measured results frequently differ from published data because consumer revolvers feature varying cylinder gap tolerances. Priority must always remain with modern, officially pressure-tested manufacturer limits.
.357 Magnum Pressure And Safety
Safety is paramount when using .357 Magnum reloading data. The standard SAAMI maximum average pressure is 35,000 PSI.
Because the .357 Magnum cartridge is identical to the .38 Special (save for being 0.135 inches longer), it is physically impossible to chamber a .357 Magnum cartridge in a .38 Special revolver. However, reloaders utilizing fast-burning powders (like Titegroup or Bullseye) for mid-range target loads must exercise extreme caution. These dense powders occupy very little space inside the long case. It is incredibly easy to accidentally double-charge a case without the powder overflowing. Reloaders must use strict visual checks inside every single case before seating a bullet to prevent a catastrophic, firearm-destroying explosion.
Best Sources For .357 Magnum Reloading Data
The strongest and most authoritative sources for safe .357 Magnum load development include:
- Hodgdon Reloading Data Center: Provides the most extensive, free online data specifically highlighting the exceptional performance of Hodgdon H110, Winchester 296, and Lil’ Gun for full-power magnum loads.
- Hornady Handbook of Cartridge Reloading: The definitive source for loading Hornady’s 0.357-inch XTP projectiles, offering distinct sections for handgun and rifle data.
- Lyman Cast Bullet Handbook: The absolute best resource for reloaders utilizing hard-cast lead semi-wadcutters, which are incredibly popular in this caliber for economical target practice and hunting.
- Alliant Powder Reloader’s Guide: The benchmark source for traditional recipes using Alliant 2400 and Unique.
Common .357 Magnum Reloading Data Questions
Where can I find .357 Magnum reloading data?
Authoritative data is published in the Hornady Reloading Handbook, the Lyman Reloading Handbook, and free online via the Hodgdon Reloading Data Center.
What powders are used in published .357 Magnum data?
Common powders for maximum velocity include Hodgdon H110, Winchester 296, Alliant 2400, Accurate No. 9, and Hodgdon Lil’ Gun. Mid-range loads frequently utilize Alliant Unique, Winchester 231, or Hodgdon Titegroup.
What bullet weights have .357 Magnum reloading data?
Published data covers 110-grain lightweight jacketed hollow points up to heavy 180-grain hard-cast lead and jacketed hunting bullets.
What is the best source for .357 Magnum reloading data Hodgdon?
The official Hodgdon Reloading Data Center provides the most up-to-date and rigorously pressure-tested data for all Hodgdon, IMR, and Winchester brand powders.
Why does .357 Magnum reloading data vary between sources?
Variations occur due to differences in bullet profile, unvented universal receiver barrels versus vented revolver test barrels, and differing laboratory chamber tolerances.
Does barrel length affect .357 Magnum velocity?
Yes. An 18-inch lever-action rifle barrel will consistently yield velocities 300 to 400 fps higher than a standard 4-inch revolver barrel using the exact same load.
Can the same powder charge be used with a different bullet?
No. Different bullet profiles, materials (cast lead vs copper jacketed), and bearing surfaces alter internal case capacity and friction, which dramatically changes chamber pressures.
What is the difference between starting and maximum published load data?
The starting load is the safe baseline for working up a new recipe. The maximum load is the highest pressure limit established safely by a ballistic laboratory.
Where can I find pressure-tested .357 Magnum data?
Pressure-tested data is available directly from major bullet and powder manufacturers, including Hornady, Hodgdon, Speer, and Lyman.
Does Hodgdon publish .357 Magnum reloading data?
Yes. Hodgdon provides extensive data for their incredibly popular H110, W296, and Lil’ Gun powders on their official online Data Center.
Does Hornady publish .357 Magnum reloading data?
Yes. Hornady publishes incredibly comprehensive load recipes tailored specifically for their .357-inch XTP projectiles, separated by handgun and rifle applications.
Does Nosler publish .357 Magnum reloading data?
Yes, Nosler provides detailed load data for their jacketed handgun bullets, covering popular defense and hunting weights like their 158-grain JHP.
Does Speer publish .357 Magnum reloading data?
Yes. The Speer Reloading Manual offers extensive pressure-tested data for their renowned Gold Dot hollow points and deeply seating lead semi-wadcutters.