One dead on and one always to the left?

[SMF]

I'm getting two points of impact from two different loads at the same range. A Berger 168 grain VLD at 2780 FPS is impacting 3/10ths of a mil left if 175 grain SMKs but vertical the same. Same weapon system, same support (sand bags), same shooter. I could understand a higher or lower point of impact but what would cause it the lighter faster bullet to shift to the left? Could it be that the VLD hasn't stabilized at 100 meters? I get the exact same results every time.


Thanks

Steve

 

[Sully2]

how much is 3/10's of a mill at that distance ( in inches)??

 

[Greyfox]

I'm getting two points of impact from two different loads at the same range. A Berger 168 grain VLD at 2780 FPS is impacting 3/10ths of a mil left if 175 grain SMKs but vertical the same. Same weapon system, same support (sand bags), same shooter. I could understand a higher or lower point of impact but what would cause it the lighter faster bullet to shift to the left? Could it be that the VLD hasn't stabilized at 100 meters? I get the exact same results every time.


Thanks

Steve

I have had that happen over the years on several occasions and believe it to be a specific bullet or load inducing different barrel harmonics causing a different POI.

 

[guns_and_labs]

I have had that happen over the years on several occasions and believe it to be a specific bullet or load inducing different barrel harmonics causing a different POI.

I've had the same experience with my .300 WinMag.

 

[Mike 338]

What Greyfox said. Bullet weight can be a significant change but any component change can move things around.

.3 mils @ 100 yards is about 1.2 inches.

 

[SMF]

Barrel harmonics, hmmm I didn't even consider that! That would certainly make sense. Thank you sir.

Steve

 

[royinidaho]

That's not to be unexpected.

One of my rifles shoots a Sierra 90 gr hp @3400 exactly 1/2" to the left of where it puts the 130 gr bullet.

Easy adjustment when switching from hunting bigger game to varmints/predators.

All my other rifles shoot one bullet weight.

 

[Joe King]

Take a long piece of wire 2ft long hold about 6" of it on a table and tap the other end, that's roughly the pattern your barrel makes when you shoot, exaggerated but it gives you the idea