168 Berger Hybrid new POA

[dmp0309]

I've changed from 168 SMK to 168 Berger Hybrid Target bullets and my point of impact is consistently about 5" (over a mil) to the right with the bergers. I can't figure out why there is such a big shift. I've gone back and forth to confirm the POI/POA shift and it remains consistent.

Background data:
.308 Model 700PSS, 26"
glassed in and timney Hit Trigger (shouldn't matter here)
Consistently .4 or better MOA


new Lapua Brass
BR2 primers
Varget 44.5
depth 2.336
around 2700 fps (both in SMK and Berger)

Any ideas why the Berger is impacting wide right?

 

[Barelstroker]

I've changed from 168 SMK to 168 Berger Hybrid Target bullets and my point of impact is consistently about 5" (over a mil) to the right with the bergers. I can't figure out why there is such a big shift. I've gone back and forth to confirm the POI/POA shift and it remains consistent.

Background data:
.308 Model 700PSS, 26"
glassed in and timney Hit Trigger (shouldn't matter here)
Consistently .4 or better MOA


new Lapua Brass
BR2 primers
Varget 44.5
depth 2.336
around 2700 fps (both in SMK and Berger)

Any ideas why the Berger is impacting wide right?

A different projectile with different shape characteristics will drift more or less when compared.
When I adjust wind to zero in the "Applied Ballistics" App, there is a fairly pronounced difference between projectile drift at the same range..eg 1000 meters.
It has to do with the shape of the projectile which directly effects the dynamic stability which in turn is tied to the gyroscopic stability or vise versa.

 

[nn8734]

I've changed from 168 SMK to 168 Berger Hybrid Target bullets and my point of impact is consistently about 5" (over a mil) to the right with the bergers. I can't figure out why there is such a big shift. I've gone back and forth to confirm the POI/POA shift and it remains consistent.

Background data:
.308 Model 700PSS, 26"
glassed in and timney Hit Trigger (shouldn't matter here)
Consistently .4 or better MOA


new Lapua Brass
BR2 primers
Varget 44.5
depth 2.336
around 2700 fps (both in SMK and Berger)

Any ideas why the Berger is impacting wide right?

Are the bergers shooting tight? Is the poi the same time after time (ie there’s no “wondering zero” - sounds like it is)?

If so, then rezero for the bergers, make note of the POI difference between the load w/the match kings in your records and move on.

Barrel harmonics is likely the reason, assuming your answer to my two questions is “yes”.

 

[Barelstroker]

I've changed from 168 SMK to 168 Berger Hybrid Target bullets and my point of impact is consistently about 5" (over a mil) to the right with the bergers. I can't figure out why there is such a big shift. I've gone back and forth to confirm the POI/POA shift and it remains consistent.

Background data:
.308 Model 700PSS, 26"
glassed in and timney Hit Trigger (shouldn't matter here)
Consistently .4 or better MOA


new Lapua Brass
BR2 primers
Varget 44.5
depth 2.336
around 2700 fps (both in SMK and Berger)

Any ideas why the Berger is impacting wide right?

You haven't specified the range you tested at so I've assumed you're referring to long range differences after zeroing the new projectile.
If the ranges are short, the differences in the drift won't be anything like 5".
As nn8437 says, the POI can & usually is effected by the barrel harmonics so you have to zero the new projectile as a matter of course which, I had assumed you had done.
My 1st post was referring to the difference between the two projectiles POI difference at long range.

 

[dmp0309]

You haven't specified the range you tested at so I've assumed you're referring to long range differences after zeroing the new projectile.
If the ranges are short, the differences in the drift won't be anything like 5".
As nn8437 says, the POI can & usually is effected by the barrel harmonics so you have to zero the new projectile as a matter of course which, I had assumed you had done.
My 1st post was referring to the difference between the two projectiles POI difference at long range.

Thanks you all.

I agree with the barrel harmonics. There is no guessing and the bullets fly true every shot with no fliers. testing was up close at 100 yards. I've zeroed to the bergers and noted the POI change for the SMKs in DOPE. Was really surprised with the mil plus change. I'm considering getting a barrel tuner and experimenting a bit there down the road. Before that I'll test the heavier berger bullets to see if this is specific to the 168g.

Thanks again for the replies

Dave

 

[Thomas Irwin]

Spin drift or harmonics won’t have that kind of effect at 100. Putting a 1lb supressor on my 20” induces only a 1 moa .Have you tested concentricity? When I went from Sierra to Berger VLD I figured my RCBS seating stem was fine. I was getting irregular shifts and switched to Reddig micrometer seating due. Not sure whether the old loads had a concentricity problem but the new die sorted the issue.

 

[dmp0309]

Spin drift or harmonics won’t have that kind of effect at 100. Putting a 1lb supressor on my 20” induces only a 1 moa .Have you tested concentricity? When I went from Sierra to Berger VLD I figured my RCBS seating stem was fine. I was getting irregular shifts and switched to Reddig micrometer seating due. Not sure whether the old loads had a concentricity problem but the new die sorted the issue.

Appreciate it- I haven't checked concentricity, but that would make sense. I'm using a standard Hornady seating die with the micrometer on top. Have been considering getting one made for the hybrid bullet. Will give this a shot. Thanks for the reply