Hammer bullets at long range….

[Dialing Long Distance]

I just had some wierdness today while shooting… I picked up some Hammer bullets, 338's 285 grain. They shoot great out to about 800 yards, like less that half minute. At 950, they are haywire. Over 1 MOA. I shot 5 in a row in one string, 3 at 950, the last 2 at 600. At 950, those 3 are about 6 inches in a triangle. At 600, the last 2, were literally a half inch apart. My velocities that I've measured on my magnetospeed are averaging 2766 fps with an ES of 10 and SD of 4.4. Seating depths are all within .001" on my comparator. It's a 9 twist Brux barrel. All my groups at 800 yards and under are really nice, (.5 MOA or under) the stuff at my 950 yd steel are not. I'm in the process of cleaning my bore again, want to make sure copper/carbon fouling isn't the issue. Anybody have anything like this happen? These bullets are new to me.
Thanks

 

[DoneNOut]

See what a ballistics app reads for you velocity at 850-900yds. Sounds like you are going subsonic.

 

[Dialing Long Distance]

See what a ballistics app reads for you velocity at 850-900yds. Sounds like you are going subsonic.

I thought that's what it looked like too, but they aren't subsonic until over 1500 yards… I'm stumped.

 

[RockyMtnMT]

Sounds like you are on the edge of stability. The very long copper bullets will get wonky at long range if they are not stable enough.

 

[RockyMtnMT]

It is a dynamic stability thing that is more rocket science than I am capable of.

 

[DoneNOut]

It is a dynamic stability thing that is more rocket science than I am capable of.

That's ok I see we have plenty of rocket scientists on this forum who aren't scared to explain...

 

[Dialing Long Distance]

I'm wondering about stability also. According to my calculator, the Miller Stability is 2.32. The bullets recommendation is a 9 twist bore.

 

[DoneNOut]

Same range, same day? Or does this happen on a continual basis?

 

[jebel]

At 950, they are haywire. Over 1 MOA.

At 950, those 3 are about 6 inches in a triangle.

These two statements seem at odds, or I'm not understanding.

 

[Dialing Long Distance]

Lol yeah I know. The 6" triangle was my best 3 shots at that 950. The other groups were over a minute. By a pretty fair margin.

 

[Dialing Long Distance]

Same range, same day? Or does this happen on a continual basis?

Same range. Today. Behind my house. My own range.

 

[DoneNOut]

Same range. Today. Behind my house. My own range.

Is there a creek or valley between 800-1000yds? What were the wind conditions today?

 

[Dialing Long Distance]

Straight shots flat. Low winds. Less than 5 mph. I was also shooting my buddy's 6 creed into sub half MOA at the same time. I was doing fine, until I was shooting at the 950 steel.
I have to think they are, for some reason, losing stability.

 

[RockyMtnMT]

Straight shots flat. Low winds. Less than 5 mph. I was also shooting my buddy's 6 creed into sub half MOA at the same time. I was doing fine, until I was shooting at the 950 steel.
I have to think they are, for some reason, losing stability.

What twist is the barrel? In my 9" twist we have shot them very well to about 1300y. We are also shooting at 4200' elev. My rifle is also pushing them at 3100 fps.