Horizontal change of impact with different ammo???

[zero2epiphany 4]

I was out blasting away last week on 4 hours of sleep, no food, and an inhuman about of coffee. So of course I was shooting like poo. Didnt care had the itch. But......my rifle had been sighted in using cheapo tula and on this trip I had brought some xm193 with me as well. While i expected a change in point of impact vertically (about 2 1/2inch low), I was very suprised to see that in changed over 2 inches to the right at 50 yards. Is this normal for a different loading? Or do I have some issue somewhere in my uber boomstick. Crown perhaps? Not exactly excited to the thought of using different ammo types and having a 5 inch change of poi to the right at 100 yards. Or perhaps its just the much more violent action of extraction that my rifle does with the xm193 stuff and me being so bone tired. Any thoughts?

[YOT 3,743]

POI can change drastically from ammo to ammo. I try to find a brand or load that my particular rifle "likes" and groups the best with, and stick with it.

It can take a while and some money trying to figure this out by trying different brands of ammo. You could have two identical rifles and one groups better with remington ammo and the other "likes" Tula better. This is especially true with target rifles, which usually get the best accuracy with custom handloads. If you're going to be target shooting it's better to buy a few different brands of ammo to sight in with, figure out which one gives the best group, then zero it with that ammo and stick with it. In a combat situation it doesn't matter, then you're just getting the lead downrange.

Edited July 27, 2011 by Yeoldetool

[Mike38 26]

[zero2epiphany 4]

I've had different brands of ammo change point of impact 2 inches at 100 yards, but not that much at 50 yards. But I suppose it could happen. Yes, even horizontally. Rifle barrels vibrate while the bullet is moving down the bore. The trick is getting the bullet to exit the muzzle at a repeatable time during the barrel vibration. That's where hand loading plays an important roll. Consistent bullet weights, powder charges, pressures, etc. all make for better accuracy. Even a powder charge variation of 0.2 grains,(or even less) can make the bullet exit at a different point in the barrel vibration. A few thousandths of an inch at the muzzle can mean inches at a distant target. Consistency is the key, and it's difficult to find consistent loads in brands like Wolf, Tula and Bear. Even the cheap USA made stuff like Winchester white box can have variations. Out of curiosity, I pulled and weighed some bullets from Wolf 55 grain .223. I found weight variations of plus or minus 1.5 grains. So one shot could be a 56.5 grain bullet. The next shot could be a 53.5 grain. Also that much variation in powder charges. Those two bullets could be 2+ inches apart on paper, even if the shooter performed flawlessly. With that said, it's still "in the zone" on a man sized target!

 

 

 

 

Its the change of poi so far to the right that has me so suprised. A little variation, sure but 50 yards is damned close. While sure a "hit" at 50 yards in the important stuff a total miss at 300 meters. On the other hand I never intend to ever be in a combat situation ever again and my saiga is intended to be a fun gun. As much as my subconscious disagrees.