Update POINT OF IMPACT CHANGE

I had to change lot# on my H4350 that I use to load 30-06. Brass, primer,bullet and OAL all the same I even shot some I had loaded with the other lot# just to make sure. So as always I started at min an worked up to my standard load 57gr with 168 nosler Combined Technology bullet. I have done this in the past with good results. This time all is well but the point of impact dropped over 3 inches I have not seen this much change before. I didn't have my chronograph to see if velocity was that far off. Have I just been lucky in the past or is this normal????

I have never received a reply from Hodgdon. I sent them an E-mail on Oct 12. to see if they had any reports of this from anyone else.

I went and got more H4350 and made up some rds with the lot # that shot lower and the new lot # and they both shot the same I had my chronograph this time and the lot # that shot lower and the new lot# was faster by 40-60 FPS than the first lot of H4350 so barrel harmonics must be where the difference came it to play.

this might seem like a silly question, but how would you barrel harmonics change that much without doing anything to the barrel?

I'm at a bit of a loss as to why and would welcome any input.
Just thinking that the bullet is leaving the barrel a little faster and the barrel torque maybe a little different.

Here' a link about barrel harmonics. http://www.rifle-accuracy.com/harmonics.htm

here is another link to review.

http://www.the-long-family.com/OBT_paper.htm

More good info. My head is starting to hurt.
This just means more range time.