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With the 10,4X62 I created a cartridge to fit all hunting situations, worldwide. With over 4250 ft lbs.(5700 Joule) of muzzle energy it rivals the venerable .375H&H Mag. The heavier 325gr bullet of .400 caliber in combination with its larger frontal area gives the 10,4X62 Impala an edge when it comes to stopping power.* On the other hand the 235gr (15,2g) Light Solid at almost 2900 fp delivers .30-06 like tracectory with a point blank range well over 200 yards. This makes the big round even suitable for long shots in open or mountainous terrain. Felt recoil with the light bullet is comparable to a 9,3X62 or .35 Whelen.
Taylor RN Factor: .375 H&H Mag. 300gr (19,4g) at 2560 fps ( 780m/sec).........41,1
10,4X62 Impala 325gr (21g) at 2430 fps ( 740 m/sec).........46,3
History
The idea is not new at all. If you want a big game cartridge to fit into standard Mauser 98 systems without expensive fitting you have to stick with the 11,95mm "Mauser" case head and a maximum COAL of approx. 84mm (3,3"). Then again the maximum diameter a .30-06 case can be necked up to maintain proper headspace is .411" or 10,4mm. In the July 1998 issue of the German "Deutsches Waffen Journal" gun magazin I broght a very detailed review of the .400 Brown Whelen cartridge.The wildcat cartridge described herein is, with conventional hunting bullets, a short range big game round . I managed to kill a cape buffalo in Tansania with a 350gr Swift A-Frame bullet without any problem.With the flat shooting 235gr Impala LS bullet the cartridge gains a lot of versatility and clean kills way beyond 200 yards are easy to manage. With this combination I successfully hunted plains game from Impala up to Hartebeest and Kudu in South Africa and was enthusiastic about its "knock down" performance.
Entering the 10,4X62 Impala project my main concern was the cartridge case. Beeing a .30-06 derivate the case can easily be fireformed from either .35 Whelen or 9,3X62 brass, but would it be possible to draw new cases with this extreme shoulder dimension? To my pleasent surprise German custom case maker Dieter Horneber of Fürth was able to create the tiny 40° shoulder with his hydraulic drawing machine.
The much bigger problem, as it turned out, was to settle for case and chamber dimensions. With the .400 Whelen, .400 Whelen Improved, .400 Brown Whelen and .411 Hawk there already exist 4 very similar cartridges. I decided for the .400 Brown Whelen but had to find out that, as not unkommon with wildcats, there was a mess of different dimensions for chambers, reamers, headspace gauges etc. So, with friendly support from the Vienna Proofhouse, I set the dimensions according to my version of the .400 Brown Whelen and, to avoid any mix ups, choose the metric designation 10,4X62 Impala for the cartridge and put it in for CIP registration.
High Performance even at low chamber pressure
Finally the day came wehere the pressure test barrel at the proof house was finnished and we were able to measure the first rounds. Immediately the new round showed its potential.
With less than 60grains of powder the 10,4X62 Impala outperformes much bigger Magnums and it does it at lower pressure, too. When it comes to efficiency the cartridge stands second to none!
My "buffalo load" with the 350gr A- Frame bullet gave 2231 fps (680m/s) at only 52475 psi.(3618bar) for 2592 ft lbs. (5244 Joule) of muzzle energy.
Even more efficient were, expectedly, the Impala Solids. My profen "South Africa Load" sent the 235gr LS at 2723fps (830m/s) at a moderate pressure of 48414psi (3338bar) and respectable 3869 ft lbs. (5246 J). The first test load with the 325gr RN bullet brought a pressure reading as low as 42206psi (2910 bar). And at 2257fps (688m/s) and 3677 ft.lbs.
(4985J) the load was nothing to sneeze at. I am already planning a rimmed version- 10,4X62R-Impala- for combination guns ith amaximum working pressure of 53664psi (3700bar).
Finally I developed 2 factory loads for the 10,4X62 Impala. See ballistics below:
235gr/15,2g Impala-LS /barrel length 24" * 192yards point blank range= 220 yards
| Distance |
yards |
0 |
50 |
100 |
150 |
200 |
250 |
300 |
| Velocity |
fps |
2854 |
2683 |
2537 |
2386 |
2241 |
2101 |
1965 |
| Energy |
ft.lbs |
4251 |
3784 |
3358 |
2971 |
2621 |
2303 |
2015 |
| bullet path |
inches |
-2 |
+0,4 |
+1,5 |
+1,3 |
-0,4 |
-3,9 |
-9,2 |
| Entfernung |
(m) |
0 |
50 |
100 |
150 |
200 |
250 |
300 |
| Geschwindigkeit |
(m/s) |
870 |
816 |
765 |
715 |
667 |
621 |
576 |
| Energie |
(J) |
5763 |
5074 |
4451 |
4163 |
3384 |
2935 |
2530 |
| GEE* 174 m |
(cm) |
|
+1,3 |
+3,9 |
+2,4 |
-4,0 |
-15,9 |
33,8 |
325gr/21g Impala-RN /barrel length 24" * 163 yards point blank range = 186 yards
| Distance |
yards |
0 |
50 |
100 |
150 |
200 |
250 |
300 |
| Velocity |
fps |
2428 |
2255 |
2089 |
1929 |
1778 |
1637 |
1504 |
| Energy |
ft.lbs |
4251 |
3688 |
3148 |
2686 |
2282 |
1935 |
1633 |
| bullet path |
inches |
-2 |
+0,7 |
+1,6 |
+0,6 |
-2,8 |
-9,0 |
-18,4 |
| Entfernung |
(m) |
0 |
50 |
100 |
150 |
200 |
250 |
300 |
| Geschwindigkeit |
(m/s) |
740 |
682 |
627 |
575 |
526 |
480 |
437 |
| Energie |
(J) |
5767 |
4904 |
4145 |
3480 |
2910 |
2424 |
2014 |
| GEE* 148 m |
(cm) |
|
+2,1 |
+3,9 |
-0,3 |
-12,4 |
-33,4 |
-64,5 |
* most recommended sight in range
Accuracy: Five shot groups under 1,5" at 100yards with factory ammunition are the rule and some handloads are doing even better.
We are talking about groups shot with my rifle (4X scope) from the shoulder.
Availability of guns and ammuntion:
The 10,4X62 Impala was introduced to the public at the "Jagd und Hund" trade fare in Dortmund (Germany) from Feb. 4-10,2008)
Factory cartridges: The 2 loadings listed above are available through licensed dealers since Feb. 2008
Cases: New, unprimed 10,4X62 Impala cases are available since Feb. 2008 directly from Impala Europe or licensed gun dealers
Guns: As of Feb. 2008 there exist 2 custom Mausers, two more beeing under construction. At the trade fares to come the new round will be introduced to all major manufacturers of hunting rifles.
Barrels: Ready to fit in Mc Gowen barrels are available through Impala Europe. Delivery time is approx. 4-6 weeks.
Reloading dies: Use RCBS .400 Brown Whelen dies for best results
More information available at impalabullets.at or contact me directly at ([email protected]).
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