Load data for .257 Ackley Improved + .257 | 90gr | Sierra HPBT GameKing

Recommended Powder(s): Alliant Reloder-17, Somchem S365

Load Specifications

(Use the Personalized Load Calculator below to adjust )

Bullet:	.257 \| 90gr \| Sierra HPBT GameKing
Manufacturer SKU:	1615
Bullet Weight:	90gr \| 5.8g
Bullet Diameter:	0.257" \| 6.53mm
Bullet Length:	<<locked>>
Caliber:	.257 Ackley Improved load data
Case Length (l3):	2.333" \| 59.3mm
Cartridge Length (C.O.L.):	<<locked>>
Seated Depth:	<<locked>>
Shank Seated Depth:	<<locked>>
Case Capacity:	63.0 Grains of Water \| 4.09 cm³
Primer Size:	Large Rifle (LR)
Max. allowed Pressure:	48200 psi \| 3323 bar
LID:	LID_B5791_C102
Last updated:	2026-06-09

Load data for 82 loads in caliber .257 Ackley Improved with .257 | 90gr | Sierra HPBT GameKing bullet and 41 powders such as Alliant Reloder-17, Somchem S365. The key underlying parameters are shown in the table above.

Important Notice: DO NOT go below Minimum Charge or above Maximum Charge unless there are reasons. Since xxlreloading.com has no control over the equipment and components used by the customer and the data used in connection with the website, any responsibility and liability for the results achieved is rejected. Also see our Terms of Service.

Questions regarding the load data: Please read the information in the next tab "Explanations".
A load must fulfill certain criteria to be listed in the default view below - see "powder criteria to fulfill to be listed".

Our load data might deviate from other sources - see the "most common reasons for deviations".

All loads are based on the bullet and case dimensions shown under "Load Specifications" - see "reloading suggestions" if you deviate.

You can set your specifications in the "Personalized Load Calculator".

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Our default view only displays powders/loads that fulfill certain criteria: Max pressure of a load <=90% of Max. Standardized Pressure. Fill Rate (Min FR): >80% and <100% for rife loads, >60% and <100% for pistol loads. Min. Propellant Combustion (Min z): >90% for rifle loads , >80% for pistol/revolver loads. Relax these criteria at your own risk to potentially get more powders shown in the load tables.
Case Length (Inch)
Case Length (mm)
CaseCapacity (GoW)
Min z (%)
Min FR (%)
Max FR*
Barrel Length (Inch)
Barrel Length (cm)
Safety Buffer (%)
.

Click on the desired row in the tables below to add a specific load / powder to your Diary and manage there.

Powder	Charge	FR	MaxP	%	V(0)	z
[Accurate 3100]*	<<locked>>	97%	38450	80%	**53	93%
Accurate 4350	<<locked>>	90%	42902	89%	**91	97%
Alliant Reloder-16	<<locked>>	91%	43236	90%	**20	97%
Alliant Reloder-17 👍	<<locked>>	87%	43337	90%	**50	99%
Alliant Reloder-23	<<locked>>	97%	36637	76%	**69	96%
Alliant Reloder-26	<<locked>>	97%	41249	86%	**50	96%
Bofors RP3	<<locked>>	83%	43236	90%	**54	99%
[Bofors RP7]*	<<locked>>	86%	42743	89%	**92	93%
[Hodgdon H414]*	<<locked>>	89%	43323	90%	**91	94%
[Hodgdon H4350]*	<<locked>>	86%	43033	89%	**35	92%
Hodgdon Hybrid 100V	<<locked>>	94%	43279	90%	**68	98%
[Hodgdon Superperformance]*	<<locked>>	89%	43279	90%	**04	93%
Hodgdon TrailBoss	<<locked>>	97%	33953	70%	**31	100%
[IMR 4350]*	<<locked>>	91%	43366	90%	**22	93%
[IMR 4451 Enduron]*	<<locked>>	85%	42859	89%	**95	93%
IMR 4831	<<locked>>	92%	42815	89%	**61	97%
Lovex S065	<<locked>>	88%	42844	89%	**09	95%
[Lovex S070]*	<<locked>>	89%	43062	89%	**25	94%
[Norma MRP]*	<<locked>>	97%	41060	85%	**04	92%
Norma URP	<<locked>>	90%	42786	89%	**87	97%
[Ramshot Hunter]*	<<locked>>	91%	43004	89%	**84	94%
ReloadSwiss RS 14	<<locked>>	96%	34374	71%	**80	100%
ReloadSwiss RS 60	<<locked>>	85%	42714	89%	**53	100%
ReloadSwiss RS 62	<<locked>>	90%	42728	89%	**97	96%
ReloadSwiss RS 70	<<locked>>	91%	43149	90%	**27	96%
Rottweil R 903	<<locked>>	85%	43178	90%	**51	99%
[Rottweil R 907]*	<<locked>>	86%	42743	89%	**92	93%
SNPE Vectan SP 11	<<locked>>	84%	42598	88%	**64	98%
SNPE Vectan Tubal 5000	<<locked>>	83%	43207	90%	**46	100%
[SNPE Vectan Tubal 7000]*	<<locked>>	88%	43352	90%	**63	94%
Shooters World Long Rifle	<<locked>>	88%	42844	89%	**09	95%
Somchem S355	<<locked>>	85%	43047	89%	**31	98%
Somchem S365 👍	<<locked>>	94%	43221	90%	**43	99%
[Somchem S385]*	<<locked>>	96%	43163	90%	**54	93%
Vihtavuori N150	<<locked>>	86%	42714	89%	**99	99%
Vihtavuori N160	<<locked>>	89%	42815	89%	**48	96%
Vihtavuori N550	<<locked>>	90%	42801	89%	**64	96%
Vihtavuori N555	<<locked>>	97%	40234	83%	**64	97%
Winchester 6.5 StaBALL	<<locked>>	89%	42844	89%	**25	99%
[Winchester 760]*	<<locked>>	89%	42989	89%	**84	93%
Winchester StaBALL HD	<<locked>>	97%	33112	69%	**40	95%

Max Load - Barrel Length: 23.60''

Powder	Charge	FR	MaxP	%	V(0)	z
[Accurate 3100]*	<<locked>>	92%	32619	68%	**95	90%
[Accurate 4350]*	<<locked>>	81%	30647	64%	**66	91%
[Alliant Reloder-16]*	<<locked>>	81%	31198	65%	**82	91%
Alliant Reloder-17	<<locked>>	81%	35027	73%	**33	96%
[Alliant Reloder-23]*	<<locked>>	86%	26672	55%	**51	90%
[Alliant Reloder-26]*	<<locked>>	89%	31517	65%	**58	90%
Bofors RP3	<<locked>>	81%	39958	83%	**89	98%
[Bofors RP7]*	<<locked>>	82%	37449	78%	**61	90%
[Hodgdon H414]*	<<locked>>	83%	35810	74%	**04	90%
[Hodgdon H4350]*	<<locked>>	83%	39189	81%	**43	90%
[Hodgdon Hybrid 100V]*	<<locked>>	81%	28514	59%	**77	93%
[Hodgdon Superperformance]*	<<locked>>	85%	37956	79%	**69	90%
Hodgdon TrailBoss	<<locked>>	81%	26847	56%	**60	100%
[IMR 4350]*	<<locked>>	85%	36651	76%	**64	90%
[IMR 4451 Enduron]*	<<locked>>	81%	37637	78%	**71	91%
[IMR 4831]*	<<locked>>	81%	29805	62%	**20	91%
[Lovex S065]*	<<locked>>	81%	34838	72%	**05	92%
[Lovex S070]*	<<locked>>	82%	34258	71%	**05	90%
[Norma MRP]*	<<locked>>	94%	37376	78%	**95	90%
[Norma URP]*	<<locked>>	81%	31111	65%	**72	92%
[Ramshot Hunter]*	<<locked>>	84%	33518	70%	**38	90%
ReloadSwiss RS 14	<<locked>>	81%	27282	57%	**06	100%
ReloadSwiss RS 60	<<locked>>	81%	37260	77%	**15	99%
[ReloadSwiss RS 62]*	<<locked>>	81%	30560	63%	**76	91%
[ReloadSwiss RS 70]*	<<locked>>	83%	32576	68%	**31	90%
Rottweil R 903	<<locked>>	81%	37652	78%	**23	97%
[Rottweil R 907]*	<<locked>>	82%	37449	78%	**61	90%
SNPE Vectan SP 11	<<locked>>	81%	38740	80%	**72	97%
SNPE Vectan Tubal 5000	<<locked>>	81%	39856	83%	**71	100%
[SNPE Vectan Tubal 7000]*	<<locked>>	82%	34940	72%	**56	90%
[Shooters World Long Rifle]*	<<locked>>	81%	34838	72%	**05	92%
Somchem S355	<<locked>>	81%	38305	79%	**30	97%
[Somchem S365]*	<<locked>>	81%	27992	58%	**17	94%
[Somchem S385]*	<<locked>>	92%	37710	78%	**17	90%
Vihtavuori N150	<<locked>>	81%	36564	76%	**54	98%
[Vihtavuori N160]*	<<locked>>	81%	32561	68%	**79	92%
[Vihtavuori N550]*	<<locked>>	81%	32039	66%	**76	92%
[Vihtavuori N555]*	<<locked>>	85%	27470	57%	**97	90%
Winchester 6.5 StaBALL	<<locked>>	81%	32430	67%	**59	95%
[Winchester 760]*	<<locked>>	83%	35375	73%	**90	90%
[Winchester StaBALL HD]*	<<locked>>	92%	28036	58%	**43	91%

Start Load - Barrel Length: 23.60''

Any powder missing? Then click here.

FR ... fill rate of the cartridge in percent

MaxP ... max. pressure of load in psi or bar

% ... max. pressure of load in percent of the maximum allowed pressure for this caliber

V(0) ... muzzle velocity in feet per second (fps) or meters per second (m/s)

z ... powder burnt in percent

[...] *... not dangerous but load has suboptimal powder burnt with possible characteristics such as extensive muzzle flash or inaccurate loads.

[...] ²... fill rate low - you might want to consider using a filler to ensure proper ignition.

[...] ᴾ... possible press load - work up slowly to this load while watching for signs of excessive pressure.

👍 ... recommended powder/load for this caliber and bullet combination based on its ballistic performance.

<<locked>>... you need to buy an access license to unlock the data