Published: 2026 | Last updated: May 2026
Accurate 1680 is a fast-burning, double-base spherical powder manufactured by PB Clermont in Belgium and distributed by Western Powders (Accurate) in North America. It was developed as a dedicated propellant for the 7.62x39mm Soviet cartridge and has since become the standard ball powder choice for 300 Blackout subsonic loading – a role it was not originally designed for but which its specific burn rate and density serve exceptionally well.
The powder occupies a burn rate position that is genuinely unusual: fast enough for 22 Hornet and similar small-bore rifle applications, yet slow enough for heavy magnum pistol cartridges like 500 S&W Magnum and 454 Casull. The bridge between these categories is the case-volume-to-bore-diameter relationship – small rifle cases and large-bore revolver cases with heavy bullets share a similar powder volume requirement despite their obvious differences. Accurate 1680 serves both because the physics of ignition and pressure development in both application types converges on the same burn rate need.
The powder has an established, field-verified record in 7.62x39mm carbine loading and 300 Blackout subsonic and supersonic applications. Its ball geometry meters with near-liquid consistency that no extruded powder in the same burn rate class can approach. Understanding both its capabilities and its genuine temperature sensitivity is the foundation for using it correctly.
This article is based on published manufacturer specifications, established load data, and documented field reports. Specifications and performance figures can vary between lots, rifles, and conditions. If you have loaded Accurate 1680 in practice – leave a comment below: real-world experience from the reloading bench is what separates verified data from manufacturer claims.
Powder Description and Technical Profile
Accurate 1680 is a double-base, spherical (ball) powder. The double-base chemistry – nitrocellulose plus nitroglycerin – provides the energy density that allows it to develop adequate chamber pressure in small-capacity cases like 7.62x39mm and 22 Hornet at appropriate charge weights. In large-bore revolver applications with heavy bullets, the same energy density develops working pressure in cases where the bullet fills most of the case volume and leaves limited powder space.
The spherical geometry produces the metering consistency that defines 1680’s practical reputation. Small, uniform spheres pack into a measure drum with liquid-like consistency regardless of cycling speed. On progressive press equipment, charge-to-charge variance of 0.04-0.07 grains is achievable – essentially the theoretical minimum for volumetric metering. For a reloader producing 500 300 Blackout subsonic rounds per session on a progressive press, this metering reliability eliminates the scale verification step that extruded powders require.
Bulk density is 0.950-0.965 g/cc – high for a powder in this burn rate range. In 7.62x39mm with 123-125 grain bullets, this density produces near-complete case fill at working charge weights – typically 92-97% – which supports consistent ignition and low velocity standard deviations. Good case fill eliminates the position sensitivity that fast powders at low case fill percentages can show in gas-operated firearms.
The pressure curve is fast and purposeful. It reaches peak pressure quickly relative to slower-burning powders, which serves two specific functions: in gas-operated semi-automatics, the pressure at the gas port during bullet passage is adequate for reliable cycling even in suppressed and short-barreled configurations; in 300 Blackout with heavy subsonic bullets, the powder generates enough working pressure to consistently ignite and cycle the action even at the very low velocities subsonic loads require.
Temperature sensitivity is the primary limitation. At approximately 1.0-1.5 fps per degree Fahrenheit, Accurate 1680 is notably more sensitive than single-base alternatives in the same burn rate class like Hodgdon H4198 or Alliant Reloder 7. For typical 300 Blackout and 7.62x39mm applications at moderate ranges, this sensitivity is manageable. For precision varmint applications at 400+ yards across wide seasonal temperature ranges, it requires acknowledgment and management.
Strengths:
- Best-in-class metering (0.04-0.07 grain variance) from spherical geometry – ideal for high-volume progressive press production
- High bulk density (0.950-0.965 g/cc) produces near-complete case fill in primary applications, eliminating position sensitivity concerns
- Reliable cycling in semi-automatic platforms – the pressure curve was specifically tuned for gas-operated 7.62x39mm and 300 Blackout AR platforms
- Subsonic 300 Blackout reliability – one of the few powders that produces consistent ignition and adequate cycling pressure at subsonic velocities with 200-220 grain bullets
- Broad application range – serves small-bore rifle, large-bore revolver, and large pistol cartridges from a single powder supply
- PB Clermont manufacturing consistency – European precision manufacturing with documented lot-to-lot uniformity
Limitations:
- Temperature sensitivity of 1.0-1.5 fps per degree Fahrenheit – loads developed at warm temperatures may produce elevated pressure in extreme heat and reduced velocity in sub-zero conditions
- Double-base flame temperature produces more carbon residue in gas systems and suppressors than single-base alternatives – standard maintenance discipline required
- Fast burn rate limits to small-capacity cases – 308 Winchester, 30-06 Springfield, and similar produce dangerous pressure spikes with 1680
- Not for standard pressure 300 Blackout supersonic with 110-125 grain bullets – the burn rate is slightly too fast for optimal efficiency at standard supersonic pressures; Vihtavuori N110 or Hodgdon CFE BLK are better matched for supersonic 300 Blackout
Technical Characteristics
| Property | Specification |
|---|---|
| Manufacturer | PB Clermont (Belgium) / Western Powders (NA Distribution) |
| Type | Double-Base Spherical (Ball) |
| Bulk Density (g/cc) | 0.950 – 0.965 |
| Grain Shape | Spherical |
| Coating | Graphite Surface |
| Burn Rate Category | Fast Rifle / Slow Magnum Handgun |
| Burn Rate Position | Hodgdon Relative Chart #72 |
| Temperature Sensitivity | ~1.0-1.5 fps / °F |
The 300 Blackout Subsonic Application – Why 1680 Works
The 300 Blackout subsonic application is where Accurate 1680 has built its modern reputation – and it is worth explaining precisely why its properties align with the subsonic requirement rather than treating this as accidental.
Subsonic 300 Blackout uses 200-220 grain bullets at velocities below 1,050 fps – the threshold for supersonic to subsonic transition with a silenced report. Two challenges define this application:
Challenge 1 – Adequate cycling pressure: A heavy, slow bullet in a gas-operated AR-15 must still generate enough gas port pressure for reliable bolt carrier group cycling. With very fast powders, all combustion is complete before the bullet reaches the gas port – producing insufficient port pressure. With very slow powders, pressure is still building at the port – inconsistent cycling. 1680’s specific burn rate produces peak pressure early enough for bullet stabilization but sustains adequate gas port pressure long enough for reliable cycling with heavy subsonic projectiles.
Challenge 2 – Consistent ignition at low pressure: At subsonic velocities, operating pressure is significantly lower than standard loads. Some powders ignite inconsistently at these low pressures, producing hangfires or squibs. 1680’s double-base chemistry and high surface area spherical geometry produce reliable ignition even at the reduced pressure of subsonic loads, consistent across a wide temperature range.
The result: Accurate 1680 in 300 Blackout subsonic cycling tests with suppressed AR-15 platforms shows more reliable function than either faster or slower alternatives. It is the documented standard in this application.
However – for 300 Blackout supersonic loads with 110-125 grain bullets, 1680’s burn rate is slightly too fast for optimal efficiency. Vihtavuori N110, Hodgdon CFE BLK, or Hodgdon H4198 are better matched to standard supersonic 300 Blackout loads. Use 1680 specifically for the subsonic application where it excels.
Burn Rate Comparison and Competing Powders
| Powder | Type | Density (g/cc) | Key Character |
|---|---|---|---|
| Hodgdon H110 | Double-Base Spherical | 0.940 | Slightly Faster – magnum revolver |
| Winchester 296 | Double-Base Spherical | 0.940 | Slightly Faster – = H110 |
| Vihtavuori N110 | Single-Base Extruded | 0.800 | Similar – single-base, temperature stable |
| Accurate 1680 | Double-Base Spherical | 0.960 | Reference |
| Hodgdon CFE BLK | Double-Base Spherical | 0.940 | Slightly Slower – 300 BLK specialist |
| Hodgdon H4198 | Single-Base Extruded | 0.850 | Slower – Extreme stability |
| Alliant Reloder 7 | Single-Base Extruded | 0.880 | Slower – single-base, 45-70 coverage |
| Accurate 2200 | Double-Base Spherical | 0.960 | Slower – 6.8 SPC, 7.62x39mm alternate |
vs. Hodgdon CFE BLK: CFE BLK is Hodgdon’s dedicated 300 Blackout ball powder, engineered around both supersonic and subsonic applications with a Copper Fouling Eraser additive. Its burn rate is slightly slower than 1680, making it better matched to supersonic 300 Blackout with 110-125 grain bullets. For the subsonic 300 Blackout application with 200-220 grain bullets, Accurate 1680 and CFE BLK both have published data – load development in your specific rifle determines which cycles more reliably. CFE BLK adds the copper fouling reduction benefit; 1680 is the original subsonic standard.
vs. Vihtavuori N110: N110 is a single-base extruded powder at a comparable burn rate with substantially better temperature stability (0.4-0.6 fps/°F vs 1680’s 1.0-1.5 fps/°F). Single-base chemistry produces less carbon residue in suppressors. 1680 meters better from its spherical geometry and has deeper documented data in 7.62x39mm and 300 Blackout subsonic. For suppressed shooting where bore cleanliness and temperature consistency are priorities, N110 is a legitimate alternative. For high-volume production on progressive equipment, 1680’s ball metering is the more practical advantage.
vs. Hodgdon H4198: H4198 burns slightly slower and belongs to the Hodgdon Extreme series with excellent temperature stability. It is the established choice for 22 Hornet and similar small-bore varmint applications where year-round velocity consistency matters. In 7.62x39mm, 1680’s slightly faster burn and higher density are sometimes a better fit. For 22 Hornet varmint hunting where seasonal temperature shifts affect point of impact, H4198’s Extreme stability is the more appropriate choice. For 7.62x39mm production loading, 1680’s ball metering is more efficient.
vs. Hodgdon H110 / Winchester 296: H110 and Winchester 296 are identical powders burning slightly faster than 1680, optimized for 357 Magnum and 44 Magnum at full pressure and for 300 Blackout supersonic. In 7.62x39mm, they may work in specific loads. H110 has a well-documented limitation: it must be loaded at or near maximum pressure for clean combustion – reduced loads produce dirty burning. Accurate 1680 does not carry this same minimum pressure requirement and burns more cleanly across the 300 Blackout subsonic pressure range.
Recommended Cartridges and Applications
Accurate 1680 operates at its best in applications where small case volume, high bullet weight, or intermediate-bore geometry calls for a fast-burning, high-energy powder.
| Cartridge | Bullet Weight | Application |
|---|---|---|
| 7.62x39mm | 123-125 gr | Primary historical application |
| 300 Blackout | 200-220 gr | Subsonic suppressed primary |
| 300 Blackout | 110-125 gr | Supersonic – CFE BLK may be better |
| 22 Hornet | 35-55 gr | Maximum velocity varmint |
| 6.5 Grendel | 90-100 gr | Light-bullet gas-gun |
| 450 Bushmaster | 250-300 gr | Large-bore rifle/pistol |
| 500 S&W Magnum | 350-500 gr | Maximum heavy revolver |
| 454 Casull | 300-360 gr | Full-power hunting revolver |
The 7.62x39mm is where Accurate 1680 originated. The original design brief was consistency in AK-pattern and SKS-pattern semi-automatics with 123-grain FMJ and FMJ-BT bullets. The powder’s burn rate was tuned to generate adequate gas port pressure for reliable cycling across military-specification gas system geometries. For a reloader loading 7.62x39mm at volume for carbine use, 1680’s ball metering and reliable cycling performance are its primary value.
The 22 Hornet application is the small-bore varmint use case where 1680 competes directly with single-base alternatives. The Hornet holds approximately 13 grains of water – a very small case where powder density directly affects achievable charge weights. 1680’s 0.960 g/cc density allows it to pack more charge mass into the Hornet case than lower-density alternatives, translating to slightly higher velocities with 35-45 grain bullets. The temperature sensitivity (1.0-1.5 fps/°F) is more relevant here than in 300 Blackout applications because varmint hunting extends across seasons and ranges where the velocity shift matters for point of impact.
The large-bore revolver applications – 500 S&W Magnum, 454 Casull, 450 Bushmaster – represent the case-volume-to-bore-diameter principle at the other end of the spectrum. These large cases with very heavy bullets leave relatively little powder volume after the bullet is seated, creating a case volume situation similar to the small-bore cartridges. 1680 finds its appropriate pressure range in these applications. Verify against current published Accurate data for each specific application.
Primers
Accurate 1680 in small-rifle cases responds well to standard small rifle primers for most applications. Magnum small rifle primers are appropriate for cold conditions below 15°F, 22 Hornet maximum loads, and AR semi-automatic 300 Blackout and 7.62x39mm applications.
| Primer | Type | Application |
|---|---|---|
| CCI No. 41 | Small Rifle Magnum (Mil-Spec) | Required for AR-15 semi-auto |
| CCI 450 | Small Rifle Magnum | Cold weather, dense subsonic charges |
| CCI 400 | Small Rifle Standard | General bolt-action development |
| Federal 205 | Small Rifle Standard | Consistent ignition general use |
| Winchester WSR | Small Rifle Standard | 7.62x39mm, 22 Hornet general |
| CCI BR-4 | Small Rifle Benchrest | Precision bolt-gun minimum SD |
| Remington 7-1/2 | Small Rifle Bench Rest | Hot ignition 22 Hornet |
| RWS 4033 | Small Rifle | Premium European option |
| Fiocchi Small Rifle | Small Rifle Standard | Volume production alternative |
| CCI 350 | Large Pistol Magnum | 500 S&W, 454 Casull |
| Federal 215 | Large Rifle Magnum | 450 Bushmaster, 500 S&W maximum |
For AR-15 semi-automatic platforms loading 300 Blackout and 7.62x39mm, the CCI No. 41 mil-spec primer cup is mandatory to prevent slam-fire from a free-floating firing pin. This is a safety requirement with any dense ball powder charge in semi-automatic platforms, not a preference.
For 300 Blackout subsonic with 200-220 grain bullets and dense charges, the CCI 450 small rifle magnum provides more reliable ignition than standard primers at the dense charge-to-case-volume ratio these loads present.
Metering and Equipment Compatibility
Accurate 1680’s spherical geometry is the defining loading bench advantage. On quality progressive press equipment, charge-to-charge variance of 0.04-0.07 grains is consistently achievable – the practical minimum for volumetric metering with any powder. At progressive cycling speeds of 300-500 rounds per hour, this consistency holds without degradation.
For high-volume 300 Blackout and 7.62x39mm production on a Dillon XL 750, Dillon RL 1100, or Hornady Lock-N-Load AP, 1680 flows with near-liquid consistency. The Dillon Precision Case Activated Powder Measure Assembly handles small spherical grains at high cycling rates without variance degradation.
For single-stage precision 22 Hornet loading, auto-dispensers including the RCBS MatchMaster and Frankford Arsenal Intellidropper 2.0 handle 1680 efficiently at the small 8-14 grain charge weights involved.
Static electricity management: fine spherical grains accumulate static charge in plastic hoppers under low humidity conditions. Ground the measure’s drop tube or treat the hopper interior with an anti-static dryer sheet. Static causes grains to cling to hopper walls, producing inconsistent throws that defeat ball powder’s inherent metering advantage.
Have you loaded Accurate 1680? Your practical data on charge weights, subsonic cycling reliability, 7.62x39mm accuracy, or temperature behavior helps other reloaders more than any spec sheet. Leave a comment below.
Reloading Safety Notes
All charge weights must come from current published Western Powders load data for Accurate 1680 specifically. Hodgdon’s online data tool covers Western Powders products. Do not substitute Hodgdon H4198, Vihtavuori N110, or Hodgdon CFE BLK charge weights for 1680 without independent verification.
Temperature protocol: loads developed near maximum at warm temperatures may produce elevated pressure in extreme heat. For maximum-charge subsonic or supersonic loads, validate at the highest temperature you will fire the load.
300 Blackout subsonic loads are case-fill critical. At 200-220 grain bullets and modest powder charges, case fill percentage needs to be verified against published data – too little powder produces inconsistent ignition; too much approaches compression territory. Use the 70% Rule as a cross-check only; published data for 1680 in 300 Blackout subsonic is the primary reference.
Fast powders in small cases build pressure rapidly. Start 10% below the listed maximum and work up in 0.2-grain increments for small cases like 22 Hornet where the total charge range is narrow.
See the overpressure in reloading guide for systematic pressure sign identification.
FAQ
Is Accurate 1680 the best powder for 300 Blackout subsonic?
It is the most widely tested and documented ball powder for 300 Blackout subsonic cycling reliability in suppressed AR-15 platforms. Hodgdon CFE BLK is the primary modern competitor with dedicated 300 Blackout development. Both have published subsonic data; load development in your specific platform determines which cycles more reliably. 1680 has the longer documented track record in this role.
Can 1680 be used for 300 Blackout supersonic with 110-125 grain bullets?
Published data exists for 1680 in 300 Blackout supersonic, but the burn rate is slightly fast for optimal efficiency with these lighter bullets. Hodgdon CFE BLK, Vihtavuori N110, and Hodgdon H4198 are generally better matched to the supersonic application. Use 1680 specifically for subsonic where its properties are most aligned.
Why does 1680 work in both 22 Hornet and 300 Blackout subsonic – such different applications?
Both applications share a common requirement: adequate pressure development in a situation where case volume and powder volume are both small. In 22 Hornet, the case itself is tiny – 13 grains water capacity. In 300 Blackout subsonic, a 200-220 grain bullet seated deep into the case leaves a small powder volume despite the larger nominal case. Both situations require a fast-burning, high-energy-density powder to develop adequate working pressure from a small charge mass. The burn rate of 1680 is calibrated for both.
Conclusion
Accurate 1680 earns its position as the standard 7.62x39mm ball powder and the default 300 Blackout subsonic choice through documented performance in both applications. The ball geometry’s metering consistency is the best available in its burn rate class. The cycling reliability in suppressed and short-barreled AR-15 platforms is field-proven across years of suppressed shooting growth.
The temperature sensitivity (1.0-1.5 fps/°F) is the honest limitation – manageable in close-range tactical and varmint applications, worth temperature-aware load development for precision applications. The double-base carbon production in suppressors is standard behavior that regular maintenance addresses.
Choose Accurate 1680 if you load 7.62x39mm at volume on a progressive press, load 300 Blackout subsonic for suppressed AR-15 platforms, or load 22 Hornet for maximum velocity varmint work where ball metering is the priority. Choose Hodgdon CFE BLK if 300 Blackout supersonic and subsonic in the same powder with copper fouling reduction is the goal. Choose Vihtavuori N110 if 300 Blackout or 7.62x39mm precision bolt-gun loading with better temperature stability and suppressor cleanliness are the priority. Choose Hodgdon H4198 if 22 Hornet year-round varmint hunting with Extreme series seasonal consistency is the primary application.
Editor’s note: Published load data and manufacturer specifications are the starting point – not the final word. Field experience from reloaders who have actually worked with this powder is the most reliable guide to what it does in practice. If you have used Accurate 1680, share your results in the comments.
Editorial note: Originally published 2026, revised May 2026.
