Load data for .256 Mag. Gibbs + .257 | 90gr | Sierra HPBT GameKing

Recommended Powder(s): ReloadSwiss RS 52, ReloadSwiss RS 60, 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:	0.890" \| 22.6mm
Caliber:	.256 Mag. Gibbs load data
Case Length (l3):	2.173" \| 55.2mm
Cartridge Length (C.O.L.):	2.801" \| 71.1mm
Seated Depth:	0.262" \| 6.7mm
Shank Seated Depth:	0.122" \| 3.1mm
Case Capacity:	56.0 Grains of Water \| 3.64 cm³
Primer Size:	Large Rifle (LR)
Max. allowed Pressure:	49313 psi \| 3400 bar
LID:	LID_B5791_C231
Last updated:	2025-01-01
Recommended Twist Rate:	1:13 - 1:11

Load data for 114 loads in caliber .256 Mag. Gibbs with .257 | 90gr | Sierra HPBT GameKing bullet and 57 powders such as ReloadSwiss RS 52, ReloadSwiss RS 60, 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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Min z (%)
Min FR (%)
Max FR*
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Barrel Length (cm)
Safety Buffer (%)
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Use the Personalized Load Calculator to customize loads to your own specific requirements. Find more details in the help section.

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.

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
ADI AR 2208	<<locked>>	86%	43511	88%	**09	97%
[Accurate 2700]*	<<locked>>	88%	44324	90%	**43	92%
Accurate 4064	<<locked>>	86%	44208	90%	**48	100%
Accurate 4350	<<locked>>	94%	43410	88%	**84	96%
Alliant Reloder- TS 15.5	<<locked>>	87%	43990	89%	**45	98%
Alliant Reloder-15	<<locked>>	84%	43540	88%	**48	97%
Alliant Reloder-16	<<locked>>	95%	44222	90%	**23	96%
Alliant Reloder-17	<<locked>>	91%	43555	88%	**27	98%
[Alliant Reloder-23]*	<<locked>>	96%	32808	67%	**35	93%
Hodgdon CFE223	<<locked>>	86%	44179	90%	**87	96%
Hodgdon H380	<<locked>>	86%	43569	88%	**25	95%
[Hodgdon H414]*	<<locked>>	90%	44280	90%	**94	93%
[Hodgdon H4350]*	<<locked>>	96%	43700	89%	**05	92%
Hodgdon Hybrid 100V	<<locked>>	97%	42351	86%	**35	98%
Hodgdon LVR	<<locked>>	92%	43656	89%	**71	95%
Hodgdon VARGET	<<locked>>	87%	44019	89%	**18	97%
Hodgdon TrailBoss	<<locked>>	96%	33402	68%	**88	100%
IMR 3031	<<locked>>	84%	44092	89%	**64	100%
IMR 4064	<<locked>>	87%	43845	89%	**05	97%
[IMR 4166 Enduron]*	<<locked>>	88%	44382	90%	**72	93%
[IMR 4350]*	<<locked>>	94%	43976	89%	**09	92%
[IMR 4451 Enduron]*	<<locked>>	89%	43816	89%	**89	92%
IMR 4831	<<locked>>	97%	40190	82%	**86	95%
IMR 4895	<<locked>>	84%	43584	88%	**58	97%
Lovex S062	<<locked>>	85%	43859	89%	**18	99%
[Lovex S065]*	<<locked>>	91%	43685	89%	**92	94%
[Lovex S070]*	<<locked>>	93%	43990	89%	**15	93%
Norma 203B	<<locked>>	85%	43700	89%	**51	97%
Norma URP	<<locked>>	94%	43584	88%	**77	96%
Ramshot Big Game	<<locked>>	85%	44179	90%	**74	97%
[Ramshot Hunter]*	<<locked>>	96%	44382	90%	**97	94%
ReloadSwiss RS 14	<<locked>>	96%	33388	68%	**28	100%
[ReloadSwiss RS 50]*	<<locked>>	86%	44019	89%	**09	94%
ReloadSwiss RS 52 👍	<<locked>>	86%	44034	89%	**94	99%
ReloadSwiss RS 60 👍	<<locked>>	92%	43903	89%	**56	99%
ReloadSwiss RS 62	<<locked>>	95%	43903	89%	**14	96%
ReloadSwiss RS 70	<<locked>>	95%	44367	90%	**30	95%
Rottweil R 902	<<locked>>	84%	44324	90%	**02	99%
Rottweil R 903	<<locked>>	89%	43540	88%	**35	98%
[Rottweil R 907]*	<<locked>>	90%	43743	89%	**86	92%
SNPE Vectan SP 11	<<locked>>	88%	43642	89%	**64	97%
SNPE Vectan Tubal 5000	<<locked>>	87%	44164	90%	**43	100%
[SNPE Vectan Tubal 7000]*	<<locked>>	92%	43743	89%	**43	93%
[Shooters World Long Rifle]*	<<locked>>	91%	43685	89%	**92	94%
Shooters World Precision	<<locked>>	85%	43859	89%	**18	99%
Somchem S355	<<locked>>	88%	43468	88%	**28	98%
Somchem S365 👍	<<locked>>	97%	41916	85%	**87	99%
Vihtavuori N133	<<locked>>	83%	44121	89%	**43	100%
Vihtavuori N135	<<locked>>	89%	43714	89%	**99	100%
Vihtavuori N140	<<locked>>	84%	43598	88%	**89	100%
Vihtavuori N150	<<locked>>	94%	44106	89%	**15	99%
Vihtavuori N160	<<locked>>	92%	44266	90%	**51	96%
Vihtavuori N540	<<locked>>	84%	44077	89%	**18	100%
Vihtavuori N550	<<locked>>	91%	43613	88%	**71	96%
[Vihtavuori N555]*	<<locked>>	97%	35085	71%	**27	94%
Winchester 6.5 StaBALL	<<locked>>	93%	43613	88%	**05	98%
[Winchester 760]*	<<locked>>	90%	44280	90%	**94	93%

Max Load - Barrel Length: 23.60''

Powder	Charge	FR	MaxP	%	V(0)	z
[ADI AR 2208]*	<<locked>>	81%	36854	75%	**44	94%
[Accurate 2700]*	<<locked>>	85%	40828	83%	**67	90%
Accurate 4064	<<locked>>	81%	37304	76%	**90	99%
[Accurate 4350]*	<<locked>>	84%	30298	61%	**43	90%
Alliant Reloder- TS 15.5	<<locked>>	81%	36579	74%	**81	96%
Alliant Reloder-15	<<locked>>	81%	39204	79%	**46	95%
[Alliant Reloder-16]*	<<locked>>	85%	32068	65%	**82	90%
[Alliant Reloder-17]*	<<locked>>	81%	31357	64%	**95	93%
[Alliant Reloder-23]*	<<locked>>	92%	28500	58%	**84	90%
[Hodgdon CFE223]*	<<locked>>	81%	37550	76%	**30	94%
[Hodgdon H380]*	<<locked>>	81%	36724	74%	**64	93%
[Hodgdon H414]*	<<locked>>	86%	38348	78%	**46	90%
[Hodgdon H4350]*	<<locked>>	93%	40277	82%	**23	90%
[Hodgdon Hybrid 100V]*	<<locked>>	83%	27340	55%	**12	90%
[Hodgdon LVR]*	<<locked>>	83%	32619	66%	**85	90%
[Hodgdon VARGET]*	<<locked>>	81%	36521	74%	**38	94%
Hodgdon TrailBoss	<<locked>>	81%	26687	54%	**31	100%
IMR 3031	<<locked>>	81%	39436	80%	**66	100%
[IMR 4064]*	<<locked>>	81%	36318	74%	**25	94%
[IMR 4166 Enduron]*	<<locked>>	82%	37840	77%	**25	90%
[IMR 4350]*	<<locked>>	92%	40553	82%	**36	90%
[IMR 4451 Enduron]*	<<locked>>	84%	38174	77%	**54	90%
[IMR 4831]*	<<locked>>	88%	29878	61%	**13	90%
IMR 4895	<<locked>>	81%	40219	82%	**79	96%
Lovex S062	<<locked>>	81%	38696	78%	**97	97%
[Lovex S065]*	<<locked>>	83%	33576	68%	**49	90%
[Lovex S070]*	<<locked>>	88%	37376	76%	**67	90%
Norma 203B	<<locked>>	81%	38725	79%	**36	96%
[Norma URP]*	<<locked>>	84%	31198	63%	**53	90%
Ramshot Big Game	<<locked>>	81%	38247	78%	**36	95%
[Ramshot Hunter]*	<<locked>>	90%	36361	74%	**00	90%
ReloadSwiss RS 14	<<locked>>	81%	26716	54%	**67	100%
[ReloadSwiss RS 50]*	<<locked>>	81%	37536	76%	**51	91%
ReloadSwiss RS 52	<<locked>>	81%	37144	75%	**36	97%
[ReloadSwiss RS 60]*	<<locked>>	81%	30676	62%	**72	93%
[ReloadSwiss RS 62]*	<<locked>>	86%	32068	65%	**08	90%
[ReloadSwiss RS 70]*	<<locked>>	88%	34824	71%	**71	90%
Rottweil R 902	<<locked>>	81%	40799	83%	**30	98%
Rottweil R 903	<<locked>>	81%	33576	68%	**95	95%
[Rottweil R 907]*	<<locked>>	87%	40176	81%	**00	90%
[SNPE Vectan SP 11]*	<<locked>>	81%	34896	71%	**58	94%
SNPE Vectan Tubal 5000	<<locked>>	81%	36608	74%	**85	99%
[SNPE Vectan Tubal 7000]*	<<locked>>	87%	37072	75%	**02	90%
[Shooters World Long Rifle]*	<<locked>>	83%	33576	68%	**49	90%
Shooters World Precision	<<locked>>	81%	38696	78%	**97	97%
Somchem S355	<<locked>>	81%	34577	70%	**08	95%
[Somchem S365]*	<<locked>>	82%	25454	52%	**02	91%
Vihtavuori N133	<<locked>>	81%	41336	84%	**87	100%
Vihtavuori N135	<<locked>>	81%	33634	68%	**72	100%
Vihtavuori N140	<<locked>>	81%	40118	81%	**07	100%
[Vihtavuori N150]*	<<locked>>	81%	29356	60%	**44	94%
[Vihtavuori N160]*	<<locked>>	82%	31183	63%	**13	90%
Vihtavuori N540	<<locked>>	81%	39900	81%	**33	99%
[Vihtavuori N550]*	<<locked>>	82%	31299	63%	**56	90%
[Vihtavuori N555]*	<<locked>>	91%	28935	59%	**40	90%
[Winchester 6.5 StaBALL]*	<<locked>>	81%	29501	60%	**41	92%
[Winchester 760]*	<<locked>>	86%	38348	78%	**46	90%

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.