Different bullet weights, different Horizontal impact?

Hi! Old shooter, new member!
I recently went out to the range to try out 2 new loads. The rifle is a Interarms Mark X 270win in a B&C stock. Scope is a Leupold VX III. Stock bbl and action are lapped and bedded, brass is prepped and neck turned. One load was a 110gr Sierra SP, the other a Nosler 140 gr Ballistic Tip. The elevation impact was 2" (expected), but the windage was 3.25" difference at 100yd.

Have I pissed off the 'Bullet Fairy' somehow?

 

I have had a couple of factory sporter weight barrels that do the same thing. The pattern in which a barrel vibrates usually shows up as an eliptical pattern. Most often there is more vertical than horozontal in a right twist barrel it typically goes from 2 o'clock to 8 o'clock or something similar. One of the factory barrels I had the misfortune of having would string horozontally 2 moa+ but with very little vertical. A great load would literally be 1/4 moa tall and 2 1/4 inches wide at 100 yds.

The other horrendous barrel I had would string vertically until a certain pressure node was reached, then it started slinging them sideways like the other one. In both cases I re-barreled and the problem went away.

In your case, you are likely just seeing the extremes of your vibration pattern because the 2 bullets are fairly far apart in weight. It is not unusual at all. As long as it groups I wouldn't be concerned.

 

I’d be more concerned with the plastic and foam stock and the interarms action than bullet weight

 

1. The cause may be deflection of the barrelled action in the stock by primary recoil forces. It may also be deflection of the entire rifle which reflects the manner of holding or stock fit to the shooter. Keep in mind, there is always some movement while the bullet is still in the barrel. This movement is likely to be greater with a heavier bullet which in the barrel for a longer period of time. WH