The 7mm Fatso - The Ultimate Short Magnum!
With drop charts done once more it was time to go hunting! We headed off on a quick trip to the South Island for the whole family over the summer holidays to have a look around Canterbury University where Jamie was enrolling and to squeeze in a bit of hunting. After leaving Christchurch, we headed up the Godley for a flying visit to see some Himalayan tahr, enduring midday temperatures approaching 40°C (104°F) in the high country. No mature bulls were seen on public land and we left the young bulls to grow but the boys had some fun climbing the bluffs and shooting a few nannies while mum watched from the valley floor.
A good friend Duncan took us for a quick look for a wallaby one evening near the Hunter Hills and the boys sniped four around 600 yards with their lightweight hunting rifles while I spotted for them. What great sport these were and I wished I'd brought along my 240 Gibbs long range varmint rifle! Heading north, we had one night in North Canterbury chamois country, but got there a little late for an evening hunt.
The next morning I pointed the boys up a likely looking valley while Fi and I packed up camp to make sure we made the ferry crossing back to the North Island later that day on time. After an hour the boys radioed up to say they hadn't seen anything and what do these chamois looked like anyway? Five minutes later they radioed back to say James had spied one on some bluffs at the head of the valley and they were heading off on a stalk.
Twenty minutes later a shot echoed down the valley and they radioed up to say they thought Jamie had shot a good buck but they were off to stalk another one they had seen. A little while later more shooting was heard and eventually both boys appeared carrying a chamois head each. Jamie had shot a lovely 9 1/2 inch buck with great hooks at 420 yards and then Willie had used Jamie's rifle to shoot a nanny at 575 yards on top of a bluff. Both boys were very pleased with yet another new species under their belt.
A 9 1/2 inch buck, not bad for your first chamois!
Willie and his first chamois. 162 grain A-Max load at 575 yards.
After a week at home to tidy up some work, we flew in with Heli-Sika on our annual school holiday trip into the Kaweka mountain beech area. We were sharing the area with Sam Bindon and his 10-year-old son Matt who had flown in with another operator. Willie had a couple of mates along as well so night times in the hut were very entertaining! The first deer to fall to Jamie's rifle was on the second morning when we had spotted a yearling asleep on a tiny clearing while a couple of hinds were sunning themselves on a bush knob higher up 600 yards away. Sam shot the yearling with Willie's 25/284 and then Jamie quickly dropped one of the hinds before they disappeared into the bush.
Sam Bindon and his 10-year-old son Matt with Sam's sika.
Later the next day after 3 fell to other rifles, Jamie spied another hind as she appeared briefly on a waterfern clearing 700 yards away not long before dark with no time to get closer. A careful shot later and it was two for two for the new gun. On our last day while hunting in a new area, Jamie pulled off a wonderful shot at 760 yards during a brief clearance in the heavy cloud we experienced that day. The 162 grain A-Max load performed superbly in sometimes windy conditions with one shot kills every time.
The longest shot so far for the 7mm Fatso - a sika at 760 yards on our last day during a clearance in the cloud.
And again the result!
So has this new wildcat lived up to our original aims and objectives? Ballistically it equals the 7mm STW but in a shorter and lighter rifle. The 160 grain Accubond load is very versatile and capable of killing any game animal in New Zealand across a wide variety of ranges. For the specialist long-range applications, the 162 grain A-Max load has proved to be an excellent choice as well. By utilizing a short Remington Titanium action, McMillan's excellent rigid yet lightweight Hunters Edge stock, a fluted 26 inch number 4 contour barrel and lightweight alloy/titanium rings, we managed to keep the bare rifle weight under 6 pounds. With the addition of the new VX7 3.5-14x50 mm Leupold scope, the all up rifle weight is just over 7 pounds, making this a superbly portable rifle with quite amazing capabilities.
Have any issues arisen during the development and subsequent year of field testing of this rifle/cartridge combination? We have been monitoring headspace since fitting the Lilja barrel and it has not changed, so lug setback has not been an issue. The extraction problem with the thick brass was an issue until we turned the excess off. This is extra work but the Lapua cases have lasted 20 reloads, so I personally think the time invested is worth it. We formed up some cases out of shortened 30/378 Weatherby brass with the belt turned off and although we were able to achieve more than 50 fps extra velocity for the same pressure due to the larger internal capacity, the case life was half that of the Lapua brass. We now use US869 powder for both loads and it is producing the same velocity and accuracy with less of the velocity variation at temperature extremes that H870 is known for.
Now that Norma has released their new standard length 2.5 inch magnums based on shortened 416 cases, there is another option. These new parent cases I think will make forming Fatso brass a lot easier, and will eliminate the full length turning procedure and reduce the number of forming operations. I have some 338 Norma Magnum cases on order and will report back once I’ve tried them. They will be softer in the head and won’t last as long as the Lapua, but the ease of manufacture may well make up for that I think. We have now made some 6.5mm versions and they are proving capable of pushing the 140 grain Bergers and 142 grain SMK’s at 3350 to 3400 fps. More to come on these.
The two loads we settled on for the 7mm Fatso, Hornady 162 grain A-Max doing 3250 fps for the distance work and the Nosler 160 grain Accubond doing 3275 fps as an all-round hunting load.
Both loads shot to the same point of impact at 100 yards which was very fortunate.
The field testing has been fairly extensive with 12 animals from 5 different big game species falling to the new rifle/cartridge combination in the first year. At ranges from 80 out to 760 yards, from the Kaimanawas to Fiordland, from Sika to Wapiti, with all the extremes of weather that our high country is renown for thrown in, it has passed the test with flying colours!
Lastly, what have we named this new wildcat? We initially called it the 7mm LSM as I've said, but when good friend Neville Alexander and his son Bruce were down from Northland, Bruce was looking at one of the cases and said "Man that's a fat case, you've got to call it the 7mm Fatso!" Politically correct or not, that's the name that has stuck, the 7mm Fatso it is!
Greg Duley is editor of NZ Hunter magazine, the number one selling hunting magazine in New Zealand. He and sons Jamie and Willie, and wife Fiona are one of the most passionate and dedicated hunting families in NZ. Greg is renowned as the long range hunting expert in his part of the world.
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