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.25-08 (.25 Souper)


The .25-08 wildcat first appeared in the mid to late 1950's. Its creation was inspired by the efficient .308 Winchester cartridge and its commercial sibling, the .243. Vernon Speer, founder of Speer Bullets, suggested that a Mr. P.F Lambert of Washington D.C was the first to neck down the .308 to .257” and that for unknown reasons, dubbed the wildcat, the .25 Souper. The name .25 Souper is still used to this day although it is just as common to hear the cartridge described as the .25-08.

The .25-08 enjoyed a brief period of popularity that lasted through to the late 60's. Since then, the .25-08 has seen very limited use. This cartridge has a very small, but ardent fan base. Every year, a small number of .25-08 custom rifles are built for keen reloaders, the cartridge being favored for its versatile performance on varmints through to medium game.


The .25-08 fits a fairly unique niche. For those who don’t hunt varmints, the .25-08 offers very little over existing commercial cartridges. This cartridge comes into its own in the hands of hunters who favor a light recoiling rifle for use on varmints through to medium game. Compared to the .243, the .25-08 can be loaded with substantially heavier bullets for medium game. By the same token, the .25-08 can be loaded with light 75 grain projectiles along with excellent accuracy, performance which cannot be obtained using the .260 or 7mm08 Remington.
The .25-08 produces similar velocities to the .257 Roberts but has a much more efficient case design and is superior to the Roberts when used in short actions. As a medium game cartridge, the .25-08 is best utilized in the same fashion as the .243 and .257 Roberts with regard to shot placement. Readers are cautioned not to make the mistake of being under confident with this cartridge and adopting overly stout bullets or limiting POI to neck shots only. Using a reliable, controlled expanding projectile such as the 115 grain Nosler Partition, best performance occurs when the bullet is driven into the forwards shoulder bones of game to maximize bullet expansion and wounding. For those who prefer less meat damage, the .25-06 or .270 are much more effective cartridges for rear lung “meat saver” shots.

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Hand Loading

Brass for the .25-08 can be easily formed from either .243 or .260 cases to minimize case trimming or neck thickness issues associated with using heavier .308 brass. Medium burning rate powders such as IMR4064 and Varget give optimum velocities with 75-87 grain bullets while slower powders in the 4350 range are the most suitable for 100 to 120 grain bullets.

From the usual custom barrel length of 24” (1:10” twist), the .25-08 is capable of firing 75 grain bullets at 3350fps, 87 grain bullets at 3250fps, 100 grain bullets at 3050fps and 120 grain bullets at 2800fps. 

For bullet performance, readers are referred to the .257 Roberts text.

Closing Comments

From time to time, wildcatters have built various improved versions of the .25-08 to maximize performance from the short rifle action platform. In 1994 Australian Guns & Game editor Breil Jackson, with the help of gunsmith Peter Kay, developed an improved .25-08 which they named the .250 Humdinger. The case design featured a minimum body taper and a 45 degree shoulder angle. The Humdinger achieved working velocities of 3400fps with an 87 grain bullet and ADI2209  (H4350) powder, 3270fps with a 100 grain bullet and ADI 2213sc (H4831sc) and 3014 with 120 grain bullets again using slow burning ADI2213sc.
Suggested loads: .25-08 Barrel length: 24”
No ID   Sectional Density Ballistic Coefficient Observed  MV Fps ME
1 HL 75gr Hornady V-Max .162 .290 3350 1869
2 HL 100gr Sierra GameKing .216 .355 3050 2065
3 HL 115gr Nosler Partition .249 .389 2850 2074
Suggested sight settings and bullet paths           
1 Yards 100 220 260 300        
  Bt. path +1.5 0 -1.5 -4.9        
2 Yards 100 150 268 310 350 375 400  
  Bt. path +3 +3.6 0 -3 -7.5 -10.7 -14.4  
3 Yards 100 150 250 290 325 350 375 400
  Bt. path +3 +3.4 0 -3 -6.8 -9.9 -13.6 -17.7
No At yards 10mphXwind Velocity Ft-lb’s
1 300 8.4 2424 978
2 300 7.8 2298 1172
3 300 7.5 2214 1251
Note: Load No. 1 for varmints only.

 25 Souper final.jpg

Note, the following dimensions are based on a .25-08 wildcat based on the .243 Winchester necked up to .257". Note that the max case length for this variant is slightly longer than a wildcat based directly on the .308 Winchester case (Max case 2.015" / 51.2mm).
  Imperial Metric 
A .473 12.01
B .470 11.94
C 20deg  
D .455 11.56
E .290 7.37
F 1.460 39.62
G .240 6.40
H 2.045 51.94
Max Case 2.045 51.94
Trim length 2.035 51.64

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