Hey, Tod, I went to the range yesterday to do some further experimentation with Vihtavuori N550 and N560 in the .308 and .30-06. (These are the nitroglycerine-impregnated powders unlike the N100 series.) To say that I was impressed would be an understatement. And these days I'm so jaded that it takes quite a bit to impress me.
The .30-06 was my M700 Stainless Mountain rifle. It has a "slow" barrel. For example, the only time I've ever squeaked over 2,900 with a 150-grain bullet was when I loaded three grains over Max with Varget.
The rifle is incredibly accurate, though, for such a lightweight hunting rifle. At least, it's accurate for the first three shots. Usually, by shot four the barrel has heated enough that the group opens to a bit over 1 moa. This is normal for Rem Mountain Rifles, as I'm sure you know from personal experience.
Anyway, I tried it with N550 and 155-grain Hornady AMAX bullets. I started with 58.5 grains and found the average to be a little over 2,950. I finished with 61.5 -- and you're not going to believe this -- the chronograph averaged well over 3,150!
Accuracy wasn't too bad -- a little over 1 moa at 200 metres. But that rifle has always preferred slightly heavier bullets.
Next, I tried N560 with a 165 Hornady BTSP. The best load was 64 grains. Velocity pushed 3,000 for the first three shots. All three were touching AT 200 METRES!. By the fourth shot, the barrel had heated up quite a bit, and it registered 3,100 over the chronograph. That shot landed about two inches lower than the group. Not surprising, considering the velocity spike. Even including that flyer, however, I would have still got 1 moa. Without the flyer, you're talking in the high .2s. This with a Hornady blemished reject hunting bullet that I bought in bulk. Not bad.
I've worked up a similar load with a 168 Barnes Triple Shock. I figure that should do the job for all my hunting needs in BC.
I'm certain that other .30-06s would get higher velocities with this powder, if you can believe it. The only thing to be aware of is that this much slow burning powder in a .30-06 gives you the blast of a .300 Magnum. Actually the fireball and blast was so intense that I think the Finns might have actually added some plutonium into that powder.
In the .308, I tried one load: 50 grains N550 pushing a 155 Hornady AMAX out of a 26-inch Krieger Palma contour barrel. I got the first three shots into a hole about the size of a dime at 200 metres. A puff of wind caught me on the fourth shot and blew it a little over one inch to 9:00. As you can imagine, that pissed me off.
The chronograph was averaging around 3,100. Yes, I'm serious. Unlike the .30-06 described above, this Krieger is a "fast" barrel. (For example, 45 grains of Varget with the same bullet will give me 2,880. That's about 100 fps faster than book velocity.) Still, you have to be amazed by 3,100 fps out of a .308 with a 155-grain bullet.
This was a maximum load. I think I'll try to back off a few grains, because I really don't need that kind of velocity out of a .308 match rifle, and I want to preserve barrel life. But this is one hell of a start.
If this powder weren't so damned expensive, I'd think seriously about using it in competition. Unfortunately, Varget from Higginson is so much cheaper and is still an excellent performer.
Anyway, I'd recommend that you try some of this powder. If you're not doing high-volume shooting, the cost may not be too bad for you, and the performance is pretty impressive.
