Major POI changes

[rommelrommel]

So, went out to play with my 1895XLR in 45/70.

Once I got the scope dialed in, all my groups were reasonable, well under 2" at 100 yards.

I had three kinds of factory ammo, and 1 set of handloads.

5 rounds of 300gr Winchester was dead on. Then 5 rounds of 300gr Federal was centered 6" right, same elevation. Then 5 rounds of 325 gr Hornady Leverevolution was right back to dead on. Then 5 rounds of 350gr Speer Hot-Cor, 42gr RL7 was centered 5" right, 1" down. Down I attribute to the heavier bullet at a modest velocity... but what's causing the wild right/left POI changes I don't quite understand.

Any ideas? I don't plan to shoot factory anymore unless I'm in a pinch... but I'd hate to get stuck hunting and buy a box and have no idea where it's gonna shoot. I've never seen variance like this in factory ammo before.

 

[H4831]

We are experimenting with virtually the same rifle and many combinations of powder and charges. The bullets are all cast, 420 grain.
I have been really surprised at how it just prints them higher or lower, depending on the speed of the bullet, of different loads. Slow loads go low and the highest loads as much as eight inches higher, but always straight up and down.
Then we tried some 350 grain factory ammo and they went 3 to 4 inches right at 100 metres.

 

[Lefty Dick]

Barrel Harmonics are the gremlin your after, bullet bearing surface, jacket metal hardness diffrences, and even velocity will make the barrel oscillate diffrently with diffrent bullets. Some rifles are more prone to the lateral shifts, likely something to do with machined stress, and dimensional diffrences.

It's more common than you think.