Load data for .256 Mag. Gibbs + .257 | 120gr | Sierra HPBT GameKing

Recommended Powder(s): Alliant Reloder-16, Alliant Reloder-26, ReloadSwiss RS 62, Somchem S365, Vihtavuori N555

Load Specifications

(Use the Personalized Load Calculator below to adjust )

Bullet:	.257 \| 120gr \| Sierra HPBT GameKing
Manufacturer SKU:	1650
Bullet Weight:	120gr \| 7.8g
Bullet Diameter:	0.257" \| 6.53mm
Bullet Length:	1.170" \| 29.7mm
Caliber:	.256 Mag. Gibbs load data
Case Length (l3):	2.173" \| 55.2mm
Cartridge Length (C.O.L.):	3.004" \| 76.3mm
Seated Depth:	0.339" \| 8.6mm
Shank Seated Depth:	0.194" \| 4.9mm
Case Capacity:	56.0 Grains of Water \| 3.64 cm³
Primer Size:	Large Rifle (LR)
Max. allowed Pressure:	49313 psi \| 3400 bar
LID:	LID_B5799_C231
Last updated:	2025-01-01
Recommended Twist Rate:	1:10 - 1:8

Load data for 104 loads in caliber .256 Mag. Gibbs with .257 | 120gr | Sierra HPBT GameKing bullet and 52 powders such as Alliant Reloder-16, Alliant Reloder-26, ReloadSwiss RS 62, Somchem S365, Vihtavuori N555. 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
[ADI AR 2209]*	<<locked>>	93%	44193	90%	**30	94%
[ADI AR 2213]*	<<locked>>	96%	44295	90%	**49	92%
Accurate 3100	<<locked>>	97%	43265	88%	**90	97%
Accurate 4350	<<locked>>	88%	44077	89%	**30	99%
Alliant Reloder-16 👍	<<locked>>	88%	43555	88%	**56	99%
Alliant Reloder-17	<<locked>>	85%	44251	90%	**89	100%
[Alliant Reloder-19]*	<<locked>>	93%	43758	89%	**23	94%
Alliant Reloder-22	<<locked>>	97%	43932	89%	**72	95%
Alliant Reloder-23	<<locked>>	97%	41278	84%	**33	100%
Alliant Reloder-25	<<locked>>	96%	35882	73%	**18	95%
Alliant Reloder-26 👍	<<locked>>	96%	44367	90%	**61	99%
Hodgdon H414	<<locked>>	83%	43801	89%	**30	96%
Hodgdon H4350	<<locked>>	89%	43961	89%	**71	96%
[Hodgdon H4831 SC]*	<<locked>>	94%	43656	89%	**90	92%
Hodgdon Hybrid 100V	<<locked>>	91%	44309	90%	**10	100%
Hodgdon LVR	<<locked>>	86%	44179	90%	**23	98%
Hodgdon Superperformance	<<locked>>	86%	43743	89%	**56	96%
Hodgdon TrailBoss	<<locked>>	96%	34461	70%	**39	100%
IMR 4350	<<locked>>	88%	44251	90%	**80	96%
IMR 4831	<<locked>>	92%	44266	90%	**20	99%
[IMR 4955 Enduron]*	<<locked>>	94%	43729	89%	**61	92%
[IMR 7828 SSC]*	<<locked>>	96%	44353	90%	**66	93%
Lovex S065	<<locked>>	85%	43526	88%	**44	98%
Lovex S070	<<locked>>	87%	44193	90%	**84	97%
Lovex S071	<<locked>>	97%	36361	74%	**52	95%
[Norma 204]*	<<locked>>	88%	43787	89%	**07	94%
Norma MRP	<<locked>>	95%	43772	89%	**08	96%
Norma URP	<<locked>>	88%	43511	88%	**23	99%
Ramshot Hunter	<<locked>>	89%	43787	89%	**33	97%
Ramshot Magnum	<<locked>>	97%	42424	86%	**23	95%
ReloadSwiss RS 14	<<locked>>	96%	34664	70%	**72	100%
ReloadSwiss RS 60	<<locked>>	85%	43801	89%	**99	100%
ReloadSwiss RS 62 👍	<<locked>>	88%	44077	89%	**49	99%
ReloadSwiss RS 70	<<locked>>	88%	43772	89%	**82	98%
[Rottweil R 904]*	<<locked>>	91%	44048	89%	**80	93%
Rottweil R 905	<<locked>>	93%	43642	89%	**26	95%
Rottweil R 907	<<locked>>	84%	44092	89%	**54	96%
SNPE Vectan Tubal 7000	<<locked>>	85%	43685	89%	**08	96%
Shooters World Long Rifle	<<locked>>	85%	43526	88%	**44	98%
[Somchem S361]*	<<locked>>	91%	44063	89%	**44	92%
Somchem S365 👍	<<locked>>	91%	43569	88%	**56	100%
Somchem S385	<<locked>>	93%	43700	89%	**00	96%
Vihtavuori N135	<<locked>>	83%	44193	90%	**15	100%
Vihtavuori N150	<<locked>>	87%	43903	89%	**41	100%
Vihtavuori N160	<<locked>>	85%	44164	90%	**94	99%
[Vihtavuori N165]*	<<locked>>	97%	40886	83%	**28	94%
Vihtavuori N550	<<locked>>	85%	43685	89%	**20	99%
Vihtavuori N555 👍	<<locked>>	96%	44367	90%	**79	99%
[Vihtavuori N560]*	<<locked>>	97%	44106	89%	**89	92%
Winchester 6.5 StaBALL	<<locked>>	87%	44092	89%	**77	100%
Winchester 760	<<locked>>	83%	43801	89%	**30	96%
Winchester StaBALL HD	<<locked>>	97%	33765	68%	**40	100%

Max Load - Barrel Length: 23.60''

Powder	Charge	FR	MaxP	%	V(0)	z
[ADI AR 2209]*	<<locked>>	85%	34432	70%	**03	90%
[ADI AR 2213]*	<<locked>>	92%	39204	79%	**35	90%
[Accurate 3100]*	<<locked>>	82%	26701	54%	**03	90%
Accurate 4350	<<locked>>	81%	35186	71%	**36	97%
Alliant Reloder-16	<<locked>>	81%	34577	70%	**49	97%
Alliant Reloder-17	<<locked>>	81%	39073	79%	**80	99%
[Alliant Reloder-19]*	<<locked>>	85%	34243	69%	**07	90%
[Alliant Reloder-22]*	<<locked>>	89%	34185	69%	**52	91%
[Alliant Reloder-23]*	<<locked>>	81%	25208	51%	**90	93%
[Alliant Reloder-25]*	<<locked>>	89%	28311	57%	**85	90%
[Alliant Reloder-26]*	<<locked>>	81%	26745	54%	**82	91%
Hodgdon H414	<<locked>>	81%	40393	82%	**61	95%
[Hodgdon H4350]*	<<locked>>	81%	33518	68%	**34	92%
[Hodgdon H4831 SC]*	<<locked>>	92%	40103	81%	**18	90%
Hodgdon Hybrid 100V	<<locked>>	81%	31894	65%	**44	97%
Hodgdon LVR	<<locked>>	81%	38014	77%	**95	97%
[Hodgdon Superperformance]*	<<locked>>	81%	36289	74%	**85	93%
Hodgdon TrailBoss	<<locked>>	87%	30052	61%	**50	100%
[IMR 4350]*	<<locked>>	81%	35375	72%	**87	93%
IMR 4831	<<locked>>	81%	30690	62%	**11	95%
[IMR 4955 Enduron]*	<<locked>>	90%	38653	78%	**56	90%
[IMR 7828 SSC]*	<<locked>>	92%	39218	80%	**48	90%
Lovex S065	<<locked>>	81%	38508	78%	**46	96%
[Lovex S070]*	<<locked>>	81%	36724	74%	**20	94%
[Lovex S071]*	<<locked>>	87%	26701	54%	**03	90%
[Norma 204]*	<<locked>>	81%	34751	70%	**03	91%
[Norma MRP]*	<<locked>>	85%	30777	62%	**80	90%
Norma URP	<<locked>>	81%	35143	71%	**36	97%
[Ramshot Hunter]*	<<locked>>	81%	34127	69%	**16	94%
[Ramshot Magnum]*	<<locked>>	90%	33460	68%	**00	90%
ReloadSwiss RS 14	<<locked>>	82%	28543	58%	**44	100%
ReloadSwiss RS 60	<<locked>>	81%	37753	77%	**61	100%
ReloadSwiss RS 62	<<locked>>	81%	34780	71%	**52	96%
ReloadSwiss RS 70	<<locked>>	81%	34200	69%	**56	95%
[Rottweil R 904]*	<<locked>>	86%	36477	74%	**16	90%
[Rottweil R 905]*	<<locked>>	85%	33011	67%	**87	90%
[Rottweil R 907]*	<<locked>>	81%	39740	81%	**59	94%
SNPE Vectan Tubal 7000	<<locked>>	81%	37739	77%	**87	95%
Shooters World Long Rifle	<<locked>>	81%	38508	78%	**46	96%
[Somchem S361]*	<<locked>>	87%	39160	79%	**46	90%
Somchem S365	<<locked>>	81%	31343	64%	**87	99%
[Somchem S385]*	<<locked>>	82%	30516	62%	**98	90%
Vihtavuori N135	<<locked>>	81%	41466	84%	**66	100%
Vihtavuori N150	<<locked>>	81%	36318	74%	**93	99%
Vihtavuori N160	<<locked>>	81%	38116	77%	**72	97%
[Vihtavuori N165]*	<<locked>>	89%	32010	65%	**18	90%
Vihtavuori N550	<<locked>>	81%	38464	78%	**12	97%
[Vihtavuori N555]*	<<locked>>	81%	27238	55%	**69	94%
[Vihtavuori N560]*	<<locked>>	93%	39088	79%	**74	90%
Winchester 6.5 StaBALL	<<locked>>	81%	36027	73%	**16	99%
Winchester 760	<<locked>>	81%	40393	82%	**61	95%
[Winchester StaBALL HD]*	<<locked>>	82%	22684	46%	**51	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.

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