Published: 2026 | Last updated: April 2026
Alliant Reloder 25 is a slow-burning, double-base extruded powder designed for large-capacity magnum cartridges where the case volume demands a burn rate that standard belted magnum powders cannot serve efficiently. It occupies the slow-magnum burn rate position in the Alliant lineup – slower than Alliant Reloder 22 but faster than Alliant Reloder 33 – and was built around cartridges like 300 Weatherby Magnum, 7mm Remington Magnum with heavy bullets, and 6.5-284 Norma at maximum velocity.
Understanding where Reloder 25 fits requires acknowledging the context it was developed in. It predates the modern temperature-stabilized Alliant powders like Alliant Reloder 26 and the temperature-focused Reloder TS series. It carries no specific temperature-stabilization additive package, which means its approximately 1.5-2.0 fps per degree Fahrenheit sensitivity is measurably higher than what modern alternatives in the same burn rate position offer. That temperature sensitivity is the primary practical limitation every Reloder 25 user needs to understand and account for.
What Reloder 25 offers in return is a large-kernel perforated cylinder geometry that creates a genuinely progressive pressure curve in large-capacity cases, and a double-base energy density that pushes maximum velocities in cartridges where case volume is the principal constraint. For the specific application it was designed for – heavy bullets in high-capacity magnums – it remains a capable, documented powder. The question for modern reloaders is whether those specific capabilities justify the temperature management protocol its sensitivity requires, compared to newer alternatives that close the velocity gap with better seasonal stability.
Powder Description and Technical Profile
Alliant Reloder 25 is a double-base, large-kernel perforated cylinder extruded powder. The combination of these physical characteristics determines nearly every practical behavior of the powder at the bench and in the bore.
The double-base chemistry – nitrocellulose plus nitroglycerin – provides higher energy density than single-base alternatives at this burn rate position. The nitroglycerin content is what allows Reloder 25 to reach adequate chamber pressure in very large cases where a single-base powder of the same burn rate would either require impractically heavy charge weights or fail to reach operating pressure at all. The energy density also produces the temperature sensitivity that is this powder’s primary limitation.
The large perforated cylinder grain geometry directly influences the pressure curve behavior. Each grain is a cylindrical stick with perforations running through its length. As the outer diameter decreases during combustion, the inner perforated surfaces expose additional burning area, maintaining more consistent total burning surface through the burn cycle than a solid grain would produce. The result is a progressive pressure curve – pressure builds more gradually and sustains longer through the bore than a solid-grain powder at the same burn rate. In a 26-28 inch barrel with a heavy 175-grain 7mm bullet, this sustained pressure profile continues pushing the bullet further down the bore than an equivalent-burning solid-grain alternative could achieve, and that sustained push is the source of the velocity advantage in long-barreled magnum rifles.
Bulk density is 0.950-0.965 g/cc – high for an extruded magnum powder. This density enables adequate case fill at appropriate charge weights in large magnum cases without reaching compressed load territory at maximum pressure. For the 300 Weatherby Magnum specifically, which demands very high charge weights to reach its characteristic velocity, the density of Reloder 25 allows those charge weights to fit in the case efficiently.
The metering limitation from the large perforated cylinder geometry is significant and honest in the original article: charge-to-charge variance of 0.3-0.5 grains is the realistic expectation from volumetric measures with large-kernel perforated powders. This is not acceptable for precision magnum loading. It requires a digital auto-dispenser or hand-weighing every charge.
Strengths:
- Progressive pressure curve from perforated cylinder geometry sustains velocity development through long magnum barrels (24-28 inches) in ways that shorter-grain or solid-grain powders at the same burn rate cannot match
- High bulk density (0.950-0.965 g/cc) enables adequate case fill in large magnum cases at appropriate charge weights without excessive compression
- Double-base energy density allows reach maximum pressure in very large cases where single-base alternatives require impractical charge weights
- Documented maximum velocity in primary cartridges – 7mm Remington Magnum and 300 Weatherby Magnum load data shows Reloder 25 at or near the top for maximum listed velocity
- Decades of published data across its primary cartridges in North American manuals
Limitations:
- Temperature sensitivity of 1.5-2.0 fps per degree Fahrenheit – the primary practical limitation. A load developed at 60°F may show pressure signs at 100°F and produce 60-80 fps less velocity at 20°F. This must be managed through temperature-specific load development
- Large kernel geometry produces 0.3-0.5 grain volumetric variance – standard volumetric powder measures cannot be used for precision loading. Digital auto-dispensers or hand-weighing are required
- Older formulation without modern stability additives – Alliant Reloder 26 with its EI impregnation technology addresses most of what made Reloder 25 necessary while providing substantially better temperature stability (0.5 fps/°F vs 1.5-2.0 fps/°F)
- Magnum primers mandatory – standard large rifle primers deliver insufficient brisance for consistent ignition of large slow-powder charges
- Not suitable for standard or medium-capacity cartridges – the burn rate is too slow for efficient combustion in 308 Winchester or 270 Winchester at standard loads
Technical Characteristics
| Property | Specification |
|---|---|
| Manufacturer | Alliant Powder (Vista Outdoor) |
| Type | Double-Base Extruded (Large Perforated Cylinder) |
| Bulk Density (g/cc) | 0.950 – 0.965 |
| Grain Shape | Large Perforated Cylinder |
| Coating | Graphite Surface Treatment |
| Burn Rate Category | Slow Rifle (Magnum) |
| Temperature Stability | ~1.5-2.0 fps / °F |
The Reloder 25 vs. Reloder 26 Question
The most important context for a modern reloader considering Alliant Reloder 25 is how it compares to its successor in the Alliant lineup: Alliant Reloder 26.
Reloder 26 was developed with Nitrochemie’s EI (impregnation) technology, which integrates energy-controlling compounds deeper into the grain structure than surface coating. The result is temperature stability of approximately 0.5 fps per degree Fahrenheit – three to four times more stable than Reloder 25’s 1.5-2.0 fps figure. It also carries an integrated tin and bismuth decoppering additive that Reloder 25 lacks.
In most primary applications, Reloder 26 either matches or exceeds Reloder 25’s velocity while delivering substantially better seasonal consistency. The cases where Reloder 25 retains an advantage are primarily the very large overbore applications where Reloder 26’s burn rate is slightly too fast – 300 Weatherby Magnum at maximum velocity with 200+ grain bullets, 7mm STW, and similar extreme-capacity cases. For standard belted magnums like 7mm Remington Magnum and 300 Winchester Magnum, Reloder 26 is generally the more appropriate modern choice.
If you are starting load development for a magnum cartridge that falls within Reloder 26’s documented range, begin there rather than with Reloder 25. Reloder 25 remains relevant for the specific larger-capacity cases where it was originally optimized and where Reloder 26 runs slightly too fast.
Temperature Sensitivity – The Management Protocol
1.5-2.0 fps per degree Fahrenheit requires explicit practical translation. A typical western North American hunting scenario involves a 60°F temperature swing between a warm September sighting-in session and a cold December or January hunt.
At 1.8 fps per degree (the midpoint of the range), a 60°F swing produces approximately 108 fps of velocity variation. In a 300 Weatherby Magnum load at 3,000 fps, that 108 fps variation shifts bullet drop at 600 yards by roughly 4-6 inches depending on the specific trajectory – a meaningful deviation for precision long-range work. At defensive hunting distances of 200-300 yards, the same velocity variation produces 0.5-1.5 inches of vertical deviation – manageable for most hunting scenarios.
The practical management protocol:
Develop loads at maximum expected hunting or competition temperatures. If you hunt in September in temperatures that may reach 85°F and in November in conditions as cold as 20°F, develop your maximum charge at 85°F to ensure safety across the full range, then confirm your drop chart at both temperature extremes.
Build a temperature-corrected drop chart. Verify velocity with a chronograph at multiple temperatures across your expected shooting range. A 40°F morning and a 75°F afternoon produce real velocity differences with Reloder 25 that show up in group vertical at 500+ yards. Knowing the velocity at each condition lets you build a drop chart that accounts for it.
Do not load to maximum in cool conditions and shoot in hot conditions. This is where temperature sensitivity becomes a safety concern rather than just an accuracy concern. A load validated at 55°F near maximum may produce excessive pressure at 95°F. Always validate maximum charge at the highest temperature you will encounter.
| Powder | Temp Sensitivity | 60°F Swing Effect | Protocol Required |
|---|---|---|---|
| Alliant Reloder 25 | 1.5-2.0 fps/°F | 90-120 fps | Full temperature development |
| Alliant Reloder 26 | ~0.5 fps/°F | 30 fps | Moderate temperature awareness |
| Hodgdon H1000 | 0.21 fps/°F | 13 fps | Minimal |
| Hodgdon Retumbo | ~0.3 fps/°F | 18 fps | Minimal |
| Norma MRP | Moderate | ~50-60 fps | Seasonal development |
Burn Rate Comparison and Competing Powders
| Powder | Type | Density (g/cc) | Key Character |
|---|---|---|---|
| Alliant Reloder 22 | Double-Base Extruded | 0.860 | Faster – standard belted magnums |
| Hodgdon H1000 | Single-Base Extruded | 0.880 | Similar-Faster – Extreme stability |
| Alliant Reloder 26 | Double-Base Extruded | 0.989 | Similar – EI technology, stable |
| Alliant Reloder 25 | Double-Base Extruded | 0.950-0.965 | Reference |
| IMR 7828 | Single-Base Extruded | 0.890 | Similar – traditional, broad data |
| IMR 7828 SSC | Single-Base Extruded | 0.930 | Similar – better metering than 7828 |
| Hodgdon Retumbo | Single-Base Extruded | 0.870 | Slightly Slower – Extreme, overbore |
| Alliant Reloder 33 | Double-Base Extruded | 0.985 | Slower – 338 Lapua, ultra-large cases |
| Norma MRP | Single-Base Extruded | 0.910 | Similar – single-base, European |
| Accurate MagPro | Double-Base Spherical | 0.950 | Similar – ball powder, better metering |
vs. Hodgdon H1000: The most important comparison. H1000 is the Hodgdon Extreme series powder at this burn rate position with 0.21 fps per degree Fahrenheit stability – seven to ten times more stable than Reloder 25. It produces somewhat less velocity than Reloder 25 in most primary applications (single-base energy deficit). For the hunter or competitor who shoots year-round across temperature extremes and wants load consistency without the temperature management protocol, H1000 is the substantially more practical choice. For the reloader who specifically needs the velocity ceiling of a double-base powder in these applications and will implement the full temperature development protocol, Reloder 25 offers more fps at comparable pressures.
vs. Alliant Reloder 26: Reloder 26 is the modern replacement for most of what Reloder 25 was used for. Better temperature stability, integrated decoppering, EI impregnation for more consistent energy release. In 7mm Remington Magnum and 300 Winchester Magnum, Reloder 26 is the current Alliant recommendation and the more appropriate powder for most reloaders. Reloder 25 retains relevance specifically in very large capacity cases – 300 Weatherby Magnum maximum velocity, 7mm STW, and similar – where Reloder 26’s burn rate is slightly too fast.
vs. IMR 7828 SSC: IMR 7828 SSC is a single-base short-cut extruded powder at a comparable burn rate with significantly better metering than Reloder 25 and lower throat erosion from single-base chemistry. Its temperature sensitivity is approximately 1.8-2.4 fps per degree Fahrenheit – comparable to Reloder 25. The tradeoffs: IMR 7828 SSC produces less peak velocity (single-base) but meters better and is available in more consistent supply. For reloaders who specifically need large magnum velocity and can tolerate the metering requirement, Reloder 25 has the velocity edge. For those who want broad magnum coverage with better metering and single-base barrel life, IMR 7828 SSC is a legitimate alternative.
vs. Hodgdon Retumbo: Retumbo burns slightly slower than Reloder 25 and belongs to the Hodgdon Extreme series with low temperature sensitivity (~0.3 fps/°F). It is specifically optimized for overbore cartridges and large magnums where the sustained pressure of a very slow Extreme series powder is the priority. For 300 RUM and 338 RUM applications, Retumbo combines Extreme stability with appropriate burn rate. Reloder 25 offers higher velocity ceiling from double-base chemistry in exchange for temperature sensitivity.
vs. Accurate MagPro: Accurate MagPro is a double-base spherical powder at a comparable burn rate. Its ball geometry meters dramatically better than Reloder 25 – essentially the defining advantage. For reloaders who load magnum ammunition at volume and need consistent progressive press charges, MagPro is the practical choice. Both share comparable temperature sensitivity from double-base chemistry.
Recommended Cartridges and Applications
Alliant Reloder 25 functions properly only in large-capacity rifle cases where the slow burn rate has room to develop appropriate pressure. Standard and medium-capacity cartridges produce incomplete combustion, excess residue, and poor standard deviations with this powder.
| Cartridge | Bullet Weight Range | Notes |
|---|---|---|
| 7mm Remington Magnum | 160-195 gr | Heavy bullet maximum velocity |
| 300 Weatherby Magnum | 180-220 gr | Flagship large-capacity application |
| 300 Winchester Magnum | 200-220 gr | Heavy bullet loads – Reloder 26 may be better for standard weights |
| 300 RUM | 190-220 gr | Ultra-mag heavy bullets |
| 338 Lapua Magnum | 250-285 gr | ELR standard weights – Reloder 33 for 285-300 gr |
| 6.5-284 Norma | 130-150 gr | Long-range overbore loads |
| 270 Winchester | 150-160 gr | Heavy bullet specialized – Reloder 26 typically better |
| 25-06 Remington | 110-120 gr | Heavy bullet overbore applications |
| 243 Winchester | 105-115 gr | Heavy 6mm – very specific application |
Important note on 270 Winchester and 300 Win Mag standard weights: For 270 Winchester with 130-150 grain bullets and 300 Winchester Magnum with 180-200 grain bullets, Alliant Reloder 26 is now the more appropriate Alliant double-base choice with better temperature stability and comparable velocity. Reloder 25 retains specific advantage in 270 Winchester only with the heaviest 150-160 grain bullets at maximum velocity, and in 300 Win Mag only with 200-220 grain heavy bullets where the slower burn rate is better matched.
The 300 Weatherby Magnum remains Reloder 25’s strongest current application. The Weatherby’s large, overbore case with its distinctive double-radius shoulder design creates a case geometry where the burn rate of Reloder 26 is sometimes slightly too fast for optimal efficiency. Reloder 25 in 300 Weatherby Magnum with 200-220 grain bullets in a 26-28 inch barrel delivers velocities that establish the cartridge’s performance ceiling.
The 243 Winchester application is strictly limited to 105-115 grain ultra-heavy bullets that are at the far end of what the 6mm bore typically shoots. With lighter 55-95 grain bullets that represent the majority of 243 Winchester use, Reloder 25 is far too slow. The application in published data reflects the case-volume-to-bore-diameter principle: heavy bullets reduce available powder space, shifting the optimal burn rate toward slower powders.
Bullets
Alliant Reloder 25 produces its best results with heavy-for-caliber, high-BC projectiles in large magnum cartridges. Light bullets in these cases cannot generate adequate start pressure for consistent ignition of a slow powder column, and they exit the bore before the progressive pressure profile has time to provide its acceleration advantage.
| Brand | Model | Weight | Cartridge | Application |
|---|---|---|---|---|
| Berger | LRHT | 175-195 gr | 7mm Rem Mag | Extreme Long Range |
| Berger | Hybrid Target | 168-190 gr | 7mm Rem Mag / 300 Win Mag | Competition |
| Hornady | ELD-X | 162-212 gr | 7mm Rem Mag / 300 Win Mag | Long-Range Hunting |
| Hornady | ELD-M | 195-212 gr | 300 Win Mag / 300 Wby | Long-Range Match |
| Sierra | MatchKing | 175-220 gr | 7mm Rem Mag / 300 Win Mag | Competition |
| Nosler | AccuBond | 175-200 gr | 7mm Rem Mag / 300 Win Mag | Bonded Hunting |
| Nosler | Partition | 175-200 gr | 7mm Rem Mag / 300 Win Mag | Classic Big Game |
| Lapua | Scenar-L | 250-285 gr | 338 Lapua | ELR Competition |
| Barnes | LRX | 168-200 gr | 7mm Rem Mag / 300 Wby | Lead-Free Long Range |
| Federal | Trophy Bonded | 165-200 gr | 300 Win Mag / 300 Wby | Premium Hunting |
Primers
Magnum large rifle primers are required for Alliant Reloder 25. The combination of large charge weights (70-95+ grains) and a slow-burning powder column creates ignition conditions where standard primers cannot deliver adequate brisance for complete, consistent ignition. Hangfires, incomplete burns showing as black-necked cases and elevated extreme spread, and inconsistent accuracy across a string are all indicators of insufficient primer energy with slow magnum powders.
| Primer | Type | Application |
|---|---|---|
| CCI 250 | Large Rifle Magnum | General magnum applications |
| Federal 215 | Large Rifle Magnum | Maximum ignition for large cases |
| Winchester WLRM | Large Rifle Magnum | Consistent hunting and match loads |
| Remington 9-1/2M | Large Rifle Magnum | Standard magnum choice |
| Federal GM215M | Large Rifle Magnum Match | Precision competition – lowest SD |
| CCI BR-2 | Large Rifle Benchrest | Competition precision where sufficient |
| RWS 5337 | Large Rifle Magnum | Premium European option |
| Fiocchi Large Rifle Magnum | Large Rifle Magnum | Consistent alternative |
Black-necked cases after firing – the indicator the original article correctly identifies – are the visible sign that ignition is incomplete and operating pressure is too low for efficient combustion. If this occurs, the first response is primer upgrade (to a hotter magnum primer if not already using one), then charge weight increase toward minimum working pressure, not maximum. Operating a slow powder below its minimum working pressure produces poor accuracy, elevated carbon residue, and potentially dangerous hangfire conditions.
Primer seating depth consistency matters more with slow magnum powders than with fast pistol powders. A primer seated 0.003 inches shallower than another delivers measurably less brisance into the powder column. Use a quality bench priming tool like the Forster Co-Ax Bench Priming Tool or K-M Primer Deluxe Hand Priming Tool to seat primers to a uniform depth.
Metering – Why Auto-Dispensers Are Required
The large perforated cylinder grain geometry of Alliant Reloder 25 creates charge-to-charge variance of 0.3-0.5 grains in volumetric powder measures. That range represents a problem: at charge weights of 75-90 grains typical of magnum applications, 0.5 grain variance is 0.5-0.7% of the charge – a percentage that directly translates to velocity and pressure variation.
The solution is straightforward: use a precision digital auto-dispenser that dispenses by weight rather than volume. The RCBS ChargeMaster Link, RCBS ChargeMaster Supreme, Hornady Auto-Charge Pro, and Frankford Arsenal Intellidropper 2.0 all dispense individual kernels to a weighed target rather than estimating by volume. The large kernels still cause some variation in the final few kernels of each charge, but the auto-dispenser’s weight-based approach limits this to ±0.1 grains rather than ±0.3-0.5 grains.
For hand-weighing, a Frankford Arsenal Powder Trickler with a high-resolution scale like the RCBS RangeMaster 2000 or Lyman Gen 6 Compact allows precise individual kernel trickling to exact weight. At charge weights of 75-90 grains, individual Reloder 25 kernels weigh approximately 0.10-0.15 grains – reasonable resolution for manual trickling to ±0.02 grains.
The 90% minimum case fill target is valid: below 90% fill with a large slow-burning charge, the powder column has room to shift away from the primer pocket when the rifle is tilted, causing position-sensitive ignition variation. Above 90% fill, the powder is consistently against the primer at firing.
Reloading Safety Notes
Temperature-induced pressure variation is the primary safety concern with Alliant Reloder 25. Loads must be developed at the highest temperature the rifle will be shot at – not in a cool loading room in autumn for a summer hunt. At 1.5-2.0 fps per degree Fahrenheit, a 40°F temperature increase produces 60-80 fps additional velocity and a corresponding pressure increase.
All charge weights must come from current published Alliant load data for Reloder 25 specifically. Do not substitute H1000, Retumbo, or Reloder 26 charge weights without independent verification. The energy density and pressure curve differences between these powders are large enough that charge weights are not interchangeable.
Start 10% below the listed maximum and work up in 0.3-grain increments. Monitor for pressure signs at every step: flattened or cratered primers, stiff bolt lift, ejector marks on case heads. In large magnum cartridges, the top 5% of the charge range can see steep pressure increases – do not skip increments near maximum.
See the overpressure in reloading guide for systematic pressure sign identification.
FAQ
Should I use Reloder 25 or Reloder 26 for 300 Winchester Magnum with 180-grain bullets?
Alliant Reloder 26 is the more appropriate current choice for 300 Winchester Magnum with 180-200 grain bullets. It provides better temperature stability (0.5 vs 1.5-2.0 fps/°F), integrated decoppering, and EI impregnation for consistent energy release – without giving up meaningful velocity. Reloder 25 retains an advantage only in 300 Winchester Magnum with 200-220 grain heavy bullets where the slightly slower burn rate is better matched.
What is the minimum barrel length for Reloder 25?
Reloder 25 benefits from at least 24-inch barrels for efficient combustion in its primary magnum applications and produces its best velocity results in 26-28 inch tubes. In 22-inch barrels, the powder may not complete combustion before the bullet exits, producing muzzle blast from unburned powder, poor standard deviations, and lower-than-expected velocity. This is the same barrel length requirement principle that applies to other slow magnum powders.
Why are my cases coming out with black-necked brass?
Black powder residue on case necks indicates the charge is below the minimum working pressure for efficient combustion of this slow powder. The response is to verify primer selection (use a magnum primer if not already), increase charge weight toward the documented minimum, and confirm case fill is at least 90%. Do not fire below-minimum charges repeatedly; inconsistent burning at low pressure is a hangfire risk.
Can Reloder 25 be used in 338 Lapua Magnum?
Yes, for 250-285 grain bullets in 338 Lapua Magnum. For the heaviest 285-300 grain projectiles in 338 Lapua where maximum ELR velocity is the goal, Alliant Reloder 33 is the more specifically optimized Alliant choice. Reloder 25 covers the middle of the 338 Lapua weight range; Reloder 33 covers the extreme-heavy end.
Conclusion
Alliant Reloder 25 is a capable, documented magnum powder from an era before temperature-stabilized double-base powders were available. It produces genuine velocity advantages in very large overbore cases – 300 Weatherby Magnum, 7mm Remington Magnum at maximum velocity with heavy bullets – through a progressive pressure curve that sustains acceleration through long barrels better than faster powders in the same application.
The limitations are equally genuine: 1.5-2.0 fps per degree of temperature sensitivity requires disciplined development protocol, large kernel geometry demands digital dispensing equipment, and the absence of modern decoppering or stability additives puts it behind current alternatives in those specific properties.
For reloaders working with 300 Weatherby Magnum, 7mm STW, or other specific large-capacity overbore cases where Reloder 26 runs slightly fast, Reloder 25 fills a defined role. For those loading 7mm Remington Magnum or 300 Winchester Magnum with standard-to-heavy bullet weights, Alliant Reloder 26 is the more modern and seasonally stable choice for most applications.
Choose Alliant Reloder 25 if you load 300 Weatherby Magnum or other very large overbore cases at maximum velocity with 200+ grain bullets, can implement the full temperature development protocol, and require the magnum dispensing equipment this powder demands. Choose Alliant Reloder 26 if you load 7mm Rem Mag or 300 Win Mag at standard-to-heavy bullet weights and want substantially better temperature stability with comparable velocity. Choose Hodgdon H1000 if temperature stability across all seasons is the absolute priority and you accept the single-base velocity trade-off.
Editorial note: Originally published 2026, revised April 2026. The revision added the dedicated Reloder 25 vs. Reloder 26 section directing modern reloaders to the more appropriate current powder for most applications, expanded the temperature sensitivity section with specific fps numbers across a realistic hunting temperature swing and the correct management protocol, corrected the 243 Winchester and 270 Winchester applications with appropriate bullet weight restrictions and Reloder 26 guidance, corrected the 338 Lapua application to note Reloder 33 for heaviest bullets, extended the bullet and primer tables with full internal links, added the black-necked case diagnostic with the correct management sequence, and added a reloading safety section with the temperature-first development protocol.
