OK, so here are the results of Sunday's range session, working up a 168 gr 308 Win load for the CZ-550 Varmint, .308 Win, 25.5" barrel, 1/12" twist. Moderate, variable winds. 77F, Baro 30.01 in, Humidity?.
Shooting from a front sport rest and rear bag, off the bench. Two identical target boards were placed at 100 yards and 200 yards down range. A third large paper target at 200 yards was used, shooting a couple of loads I already knew, just to make sure I was on paper before starting. I was testing both the Berger 168 VLD Hunter and the Nosler 165 Partition, but concentrated on the Berger because it seemed the more accurate round.
1. Getting on paper at 200 yards. The 3-shot Nosler group is about 3 in, for scale.
2. These were the target boards at 200 and 100 yards. The best Nosler 165 gr groups were the #3 targets. The Berger 168 gr groups are the 200 yard targets #4, #5 and #6, 8, 10 groups. The #6 target 200 yard group was the tightest - using 42.0gr of Varget. There are actually 4 shots in the #6, not 3. I followed with a 3-shot group of the same load at 100 yards, target #6. Both 100 yd 3-shot and 200 yd 4-shot groups were sub-MOA
200 yard board:
100 yard board:
3. I repeated another 3-shot group with the same round at 200 yards, target #8 -- same results. So, I plotted the results of all 7 200 yard POI's on a single target, #6. I came up with an average of the POI's, being 2 inches low and 1.5 inches right at 200 yards.
4. I then carefully rested the rifle on the bag and set the cross hairs on the bullseye of the #10 target at 200 yards. I carefully corrected the point of aim from the center of the bull to the center of the POI, effectively moving the POI up 2" and left 1.5". I fired two more shots at target #10 at 200 yards, both were in the bull, sub-MOA. I fired a third round at target #10 at 100 yards. The POI was about 2" high and slightly left. The 100 yard POI is plotted on the 200 yard target. Note that these 3 photos are rotated 90 deg. to fit the screen
The recipe for the Berger 168 gr VLD Hunting for the CZ-550 V is 42.0 grains of Varget, CCI 200 large rifle primer and seated to the minimum depth to allow the rounds to be fed into the magazine, COL 2.75", which also gives full length contact of the shank of the bullet with the cartridge neck.
I have 3 more of these loads from my original work up batch -- they go in the magazine and with me on my upcoming hog hunt.
Entering the data on the bullet, rifle and conditions (G7, bullet length, rate of twist, scope 1.5 in above bore zeroed at 200 yards, etc.), I played with the external ballistics program and found out that a muzzle velocity of 2650 FPS reproduced a POI +2" at 100 yards, which seems to be about right for the load. That puts the 168 gr round POI within +/- 2" elevation of the point of aim out to about 235 yards with MOA accuracy or better. It should do the trick if I do my part. :bthumb:
BTW, as you can see, the Nosler 165 Partition over 44.4 grains of Varget or 42.0 gr of Vit N140 wasn't bad, but it was neither as accurate nor as flat shooting as the 168 gr Berger, which means the Berger is retaining better down range energy, and the rifle is now zeroed for the Berger, not the Nosler.
Shooting from a front sport rest and rear bag, off the bench. Two identical target boards were placed at 100 yards and 200 yards down range. A third large paper target at 200 yards was used, shooting a couple of loads I already knew, just to make sure I was on paper before starting. I was testing both the Berger 168 VLD Hunter and the Nosler 165 Partition, but concentrated on the Berger because it seemed the more accurate round.
1. Getting on paper at 200 yards. The 3-shot Nosler group is about 3 in, for scale.
2. These were the target boards at 200 and 100 yards. The best Nosler 165 gr groups were the #3 targets. The Berger 168 gr groups are the 200 yard targets #4, #5 and #6, 8, 10 groups. The #6 target 200 yard group was the tightest - using 42.0gr of Varget. There are actually 4 shots in the #6, not 3. I followed with a 3-shot group of the same load at 100 yards, target #6. Both 100 yd 3-shot and 200 yd 4-shot groups were sub-MOA
200 yard board:
100 yard board:
3. I repeated another 3-shot group with the same round at 200 yards, target #8 -- same results. So, I plotted the results of all 7 200 yard POI's on a single target, #6. I came up with an average of the POI's, being 2 inches low and 1.5 inches right at 200 yards.
4. I then carefully rested the rifle on the bag and set the cross hairs on the bullseye of the #10 target at 200 yards. I carefully corrected the point of aim from the center of the bull to the center of the POI, effectively moving the POI up 2" and left 1.5". I fired two more shots at target #10 at 200 yards, both were in the bull, sub-MOA. I fired a third round at target #10 at 100 yards. The POI was about 2" high and slightly left. The 100 yard POI is plotted on the 200 yard target. Note that these 3 photos are rotated 90 deg. to fit the screen
The recipe for the Berger 168 gr VLD Hunting for the CZ-550 V is 42.0 grains of Varget, CCI 200 large rifle primer and seated to the minimum depth to allow the rounds to be fed into the magazine, COL 2.75", which also gives full length contact of the shank of the bullet with the cartridge neck.
I have 3 more of these loads from my original work up batch -- they go in the magazine and with me on my upcoming hog hunt.
Entering the data on the bullet, rifle and conditions (G7, bullet length, rate of twist, scope 1.5 in above bore zeroed at 200 yards, etc.), I played with the external ballistics program and found out that a muzzle velocity of 2650 FPS reproduced a POI +2" at 100 yards, which seems to be about right for the load. That puts the 168 gr round POI within +/- 2" elevation of the point of aim out to about 235 yards with MOA accuracy or better. It should do the trick if I do my part. :bthumb:
BTW, as you can see, the Nosler 165 Partition over 44.4 grains of Varget or 42.0 gr of Vit N140 wasn't bad, but it was neither as accurate nor as flat shooting as the 168 gr Berger, which means the Berger is retaining better down range energy, and the rifle is now zeroed for the Berger, not the Nosler.
