POI shift and patch thickness

I tried a few different patch combinations in my .45 TC Hawken today. My previous load was .440 ball and .015 patch. I tried both .445 ball with .015 patch, and .440 ball with .018 patch. Both combinations shot to about the same POI, which was left and low, relative to the original combination's POI. My conclusion is that the tighter ball/ patch combo spins a bit faster and as a result of the barrel having a RH twist, the ball moves left and down a bit because of the added spin drift, just like hitting a hook when playing golf. Is my understanding correct? Does this match your own experience?

No.

Pacobillie said:

My conclusion is that the tighter ball/ patch combo spins a bit faster

Click to expand...

I've had POI shifts when changing PRB combos or lube...I can't scientifically explain why but the direction of twist rotation may well enter into the direction of the POI shifts...but really don't know.

Rifling twist is what it is...ie: a 1:48" bore is only going to rotate the ball one full turn in 48" no matter the PRB combo...I guess different amounts of powder / velocity would change what I think of as the amount of torque on the PRB combo as it moves up the rifling.

Others more knowledgeable might have a more definitive answer...

I'm not sure about the explanation, but I don't think it fits my experience. I regularly shoot light (~30 grains), medium (~60 grains) and heavy (anywhere from 90 to 120 grains, depending) of powder through 50, 54 and 58 caliber rifles for different uses. Yeah, as range stretches I get some vertical movement due to velocity changes, but not enough to write home about. I've never seen a shift such as yours at 25 and 50 yards even with I suspect a whole lot more change in velocity. There's no left/right deflection with any of them.

Sorry guys. I got this backwards. The POI actually moved right and I adjusted the sights left.

Sorry about this.

It has been my personal experience that tighter combinations raise the point of impact by the fact that a tighter ball/patch combination yeilds slightly more recoil causing the barrel to rise . :idunno: :idunno:

Not enuf info to conclude anything.
What size are the groups, that is all that matters. Git yer load then adjust sights. Where you shooting from the bench? Did you have an observer that is familiar with benchrest shooting? That can be important. Your hold, breathing, amount of coffee you had that a.m., moon phases, etc. can/will affect POI.
BTW: tighter ball/patch combos can raise POI because of increased pressure. Not much but enuf to lose that 'X' score.