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 or how it happens.
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 ??

 

[mc223]

Trigger jerk

Seems far too drastic for coriolus

 

[tammons]

No flinch.
I know exactly where I was holding the rifle when I squeeze the trigger.

I shot 4 130 gr shots on the money and groups about 1"

Then shot 4 95 gr TTSX loads and high about .5 and to the right about 4"

I ran into another couple of guys with 270 win's and one with a 257 weatherby, that said when they tried light bullets in hot loads, their rifles shot off to the right a good bit. The guy with the 257 weatherby, his rifle shot to the right 4" when he went to a much lighter faster varmint load.

I think this has something to do with bullet weight vs barrel twist vs torque, but I just cant find a link on anything.

 

[RonAKA]

I have seen the effect in .22LR rimfire. There the bullet weights are usually the same (40 grains), but I find when the load gets heavier and velocity goes up, the POI tends to rise (as expected), but also goes to the left. I have rationalized that it is due to a right hand twist barrel. The bullet does not want to spin right, so it tends to un twist the barrel to the left. I presume the same could happen with a centerfire. The heavier the bullet the more it does not want to be twisted, so the more the barrel gets twisted in reverse.

Could be that, or something totally different!!

 

[mc223]

Is your action timed and trueed?
Is the barrel nut properly torqued?
Are the action screws properly torqued? You Know about adjusting the action screws to change the POI?
Is there a pressure point in the bedding that allows a freaky harmonic?


Hang a weight on the end of the barrel and see if it is some freaky harmonic.

 

[MGYSGT]

Different brands and weights will do that. Have seen it at the range before. Some one shows up with 5 different brands/loads and can't believe the spread between them.

 

[headhunter1111]

Iwouldn't imagine it making much difference but I suppose theoretically it could be the over stabilization of lighter shorter projectiles. My bet would be with MGYSGT probably just the differences in bullets.

 

[4xforfun]

Is your action timed and trueed?
Is the barrel nut properly torqued?
Are the action screws properly torqued? You Know about adjusting the action screws to change the POI?
Is there a pressure point in the bedding that allows a freaky harmonic?


Hang a weight on the end of the barrel and see if it is some freaky harmonic.

First, does a winny even have a bbl nut? I though that was a Savage thing...not sure.



Second, as far as torque...I have a bat action comp gun that I have 5 different tubes for. I sometimes switch 3 or four times during a days worth of matches. I have shot it with the bbl UBBER tight & I have forgotten to tighten it all together. I didn't even get the bbl to the reciever...about a 1/4 turn from contact with the reciever.....DUMB!!!! The four tubes chambered up by one smith all print to exactly the same point, tigheded up or not. The fifth does not hit in the same groupe, but it prints to the SAME point as it did the last time it was on...very predictable. It doesn't matter hw tignt the tube is, the group size and POI do not change.

Third. When I started switching tubes, I asked around to the pro's about how tight......I got ELEVENTEEN DIFFERENT ANSWERS. Hardly anyone agreed...so ...go figure.

Not sure about the action timed thing...could be.

Absolutely could be a PSI point between the tube and stock and could very well be improper action screw torque.

 

[whiskey08]

different bullets exiting the barrel at different points in the barrel whip.

Ive seen slow mo videos of barrels and scopes during firing. The amount of whip is very suprising. (scary when it comes to scopes) Ive also seen graphical representations of the amount of difference of whip from its most left to right at a hundred yards, and its measured in feet.

 

[DCRYDER]

Whiskey nailed it. Finally!!! Its very possible for a lighter/faster bullet to impact lower than a heavier/slower one. It all depends on where the muzzle is pointed during oscillation when the bullets exit.

And if 2 or more different barrels have the same POI it is a fluke. NO BARREL IS PERFECTLY STRAIGHT, no matter who made it. And the odds of finding 2 barrels with the same degree of crookedness that were threaded, chambered, and indexed IDENTICALLY is a "1 in 1000" chance.

 

[necchi]

different bullets exiting the barrel at different points in the barrel whip.

Exactly,

Varmit Al's barrel Harmonics page has some great action shot's and info about the phenomina.
http://www.varmintal.net/amode.htm

I guess I've never expected bullets of that great a variation to print anywhere near a 1/2" from each other. It would be really nice if we could make that happen, and maybe we can if the velocity is changed enough. But in the real world where most are after max velocities and accuracy for each load, haveing groups several inches apart is the norm.

 

[tammons]

Stringing up and down, true, but the 4" side move surprised me

Thanks for the replies everybody.
This is not a target gun.
It is my hunting rifle and if it will shoot 1/2" - 1" that is fine with me.

I did not mention that when I was testing these rounds, I did not have a death grip on the rifle. More like good cheek weld, medium grip on the palm area, but very light on the foregrip.

The forgrip part of the duromax is not that wide, so I really think it is a combination of
my lightish grip on the rifle, combined with torque sending the heavier bullets off to the left and probably barrel whip too.

I will probably just stick with one bullet for now.

I originally set up this barrel to shoot inside of 4" at 300 yards with the 95 gr TTSX so I think I will concentrate on that load, and go back to the 130 grainers later.

Just changing my grip might take care of a lot of it, and I might be able to dial in the 130 load to hit at a node similar to the 95 gr bullet.

Thanks for the help.

 

[whiskey08]

dont want to hijack the thread but here is a extreme example of a barrel and scope vibrating

http://www.youtube.com/watch?v=s5pVya7eask

 

[tammons]

I have seen that video and its amazing to me that the scope would even return anywhere close to the original zero.

 

[kelbro]

I have an A-Bolt in .270 that puts the 90gr POI about 4" right of 130s and 140s.

 

[tammons]

So far that's the 3rd 270 from different manuf's that shoots 4" to the right with light bullets.

That said all different setups, barrel lengths and different loads, so who knows.

Must be mostly torque.

 

[jonbearman]

What are the specs on your barrel ET: diameter near the reciever and taper and muzzle diameter. Also if it is one of the wimpy pencil tubes you should let it cool between shots or do 2 to 3 shot groups and then let it come back to ambient temperature as heat will increase the stress in a factory barrel due to fast production and normalizing of the steel before rifling .Places like keiger and others cryo treat the blanks during the deep hole drilling and rifling procedure.Basically you have a stressed barrel because savage does not have the time to do all this extra work.It helps in keeping costs down.I would seriously call jim briggs at Northland Supply and get a stiffer barrel.Most of his barrels are only 250.00-340.00.Check it out.

 

[jonbearman]

Are you snad bagging the rifle or just off a front bag.

 

[tammons]

10 twist sporter 22".

95% of my shot will be a cold bore shot. Rarely need to shoot twice.

Yes, I had thought about a heavier barrel.

What are the specs on your barrel ET: diameter near the reciever and taper and muzzle diameter. Also if it is one of the wimpy pencil tubes you should let it cool between shots or do 2 to 3 shot groups and then let it come back to ambient temperature as heat will increase the stress in a factory barrel due to fast production and normalizing of the steel before rifling .Places like keiger and others cryo treat the blanks during the deep hole drilling and rifling procedure.Basically you have a stressed barrel because savage does not have the time to do all this extra work.It helps in keeping costs down.I would seriously call jim briggs at Northland Supply and get a stiffer barrel.Most of his barrels are only 250.00-340.00.Check it out.

 

[tammons]

Front rest and rear bag.

Are you snad bagging the rifle or just off a front bag.