Can anyone explain this phenomenon

[tammons]

Savage 270 win, bedded duramax stock, EGW base, extreme rings, leupold scope, SSS trigger.

Problem is Lighter bullets shooting way off the the right.

I have had this happen before in other calibers but not this much. I think it is due to torque but I dont really understand what causes it. IE like a heavier bullet torques the rifle more than a light bullet ??

I loaded some 95 gr TTSX 270 win loads and went to the range today. From my calcs I should be getting about 3700+ fps with a 22" barrel. No chrono data yet.

Since the TTSX at 3700 fps is such an overkill for deer I was intending on using a 130 gr gameking for deer.

I ran the loads up to max and zeroed in with the 130 GK.
All well and good and the GK bullets shot pretty tight, considering the barrel is not even broken in and I have not worked them for accuracy.

The 130 grainer should be running at about 3100+ or so.

I figured the TTSX would hit about 1/2" higher than the 130 and it did.

What I did not expect is it hit about 4"-5" to the right.

I have had this happen before with other rifles, where a lighter bullet would move to the right, heavier to the left, but never this much.

Seems like I saw a 1"-2" move to the right in 223 or maybe it was a 22-250.

I think it is due to torque, but nobody has ever told me specifically what causes this.

Any knowledge on this one ??

 

[MitchAlsup]

Re: Can anyone explain this phenomenon

Re Torque: If torque is causing the rifle to print 4-5 inches off to the right, then you are not holding the gun correctly.

However, a big change in bullet weight, pressures, the shape of the pressure curve CAN change the POI by about this much, expecially if you have not found an accuracy node.

 

[Drifter™]

Re: Can anyone explain this phenomenon

deleted

 

[flyboy]

Re: Can anyone explain this phenomenon

Zero the scope for what you want to use and forget about it. This stuff happens.

 

[ChadTRG42]

Re: Can anyone explain this phenomenon

It is very common for different bullets to have different point of impacts. Going from a 130 grain lead bullet to a 95 grain solid copper bullet should give you a different POI. They are totally different types of bullets. Zero your rifle for what you want, then re-zero your scope for the other. If you figure out exactly where the POI shift is, you can re-zero the scope without having to shoot the rifle.

And I'll bet my left nut the 95 grain bullet isn't going 3700+ fps.

 

[RobertB]

Re: Can anyone explain this phenomenon

I would like to hear a good reason for this. Explain how one particular bullet leaves a (assumed) perfectly straight bbl, action, scope, bases+rings and flies 100 yds and hits the target while a second bullet out of the same combo/zero hits several inches to the right or left. I dont care about up or down. THen you are supposed to zero off of that and then you will be able to dial or hold for longer ranges. A bullet cant return to another direction after being fired from a different one. Or can it? I'm asking. Unless you are in a crazy unaccurate node.

 

[MitchAlsup]

Re: Can anyone explain this phenomenon

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RobertB</div><div class="ubbcode-body">I would like to hear a good reason for this. Explain how one particular bullet leaves a (assumed) perfectly straight bbl, action, scope, bases+rings and flies 100 yds and hits the target while a second bullet out of the same combo/zero hits several inches to the right or left. </div></div>

At the pressures (i.e. forces) involved, barrels are NOT stiff. They whip this way and that by up to 0.005 inches--enough to see if you have keen vision. If one bullet charge weight combination just happens to leave the muzzle when the barrel IS pointing straight, it looks golden. While another bullet charge weight varriation leaves the barrel when it is at maximum bend, it looks like crap.

That is why dialing in a load is SO SO very important.

 

[ChadTRG42]

Re: Can anyone explain this phenomenon

What Mitch said above. When you fire a round, the barrel has vibrations and whips back and forth, and up and down, ever so slightly. When you shoot different bullets (different weight, type, or profile), it can change the vibrations of the barrel (i.e., barrel whip) and the bullet may leave the barrel in a different spot in the whip. This is what causes the point of impact shift. Normally, the POI shift is predictable, and once you know what the shift is, you can dial it into your scope (or hold off). This is why having 1 load makes things easier.

 

[flyboy]

Re: Can anyone explain this phenomenon

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MitchAlsup</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RobertB</div><div class="ubbcode-body">I would like to hear a good reason for this. Explain how one particular bullet leaves a (assumed) perfectly straight bbl, action, scope, bases+rings and flies 100 yds and hits the target while a second bullet out of the same combo/zero hits several inches to the right or left. </div></div>

At the pressures (i.e. forces) involved, barrels are NOT stiff. They whip this way and that by up to 0.005 inches--enough to see if you have keen vision. If one bullet charge weight combination just happens to leave the muzzle when the barrel IS pointing straight, it looks golden. While another bullet charge weight varriation leaves the barrel when it is at maximum bend, it looks like crap.

That is why dialing in a load is SO SO very important. </div></div>

Glad you took the time. I would have butchered that explanation.