I was shooting my .416 Rigby, looking at getting the sights dialed in for my upcoming elephant hunt.

In the past, I have used Barnes solids with the flat point without trouble.

Today, the TSX load goes right to the old POA. The solid load is not on paper. I walk up to 25 yards and shoot one round and get a perfect side profile of the bullet.

The load is the same as my old load of 94 gr H4350 loaded to barnes' standard COAL which always performed fine in the past. It is a different lot of bullets, but the powder was the same.

The only thing I could think of is that this is a bit on the higher side for a Rigby load (2450 FPS) and the bullets were only marginally stabilized before.

Any thoughts? Any ideas given that I have 2 weeks to get this working?

I would double check the diameter and see if they were truly .416
If so then start backing down on the amount of powder a couple grains at a time and see if they stabilize.
Dave

1. Also check the length of the bullets and see if they are longer.

2. Weigh several bullets and see if the same alloy was used.

Guys, the faster a bullet runs the more stable it is, not the other way around. Keyholes are usually due to inadequate stability either from too slow an rpm for the bullet length or from poor grip by the lands on the bullet itself.

Perhaps the new bullets are really .411s, although I'd think you'd have noticed far lighter seating pressure. The new lot may be longer, which reduces flight stability. Or the powder charge/powder is not the same as you used before - misread scale, etc.


.

CR, Tell us about your Rigby ? What twist?
for a bullet to stabilize it has to have spin and fins. this bullet should have both.
According to the general definition of stability, a bullet may become unstable by being over-stabilized. Over-stabilization means that the bullet rotates too fast and becomes incapable of following the bending trajectory, as its longitude axis tends to keep its direction. This effect often shows up in high-angle shooting.
the bullet needs to turn nose down as the flight path begins to curve down so that it continues to fly point first. An over spun bullet will resist turning into the wind and the nose will remain turned upward relative to the ballistic curve. Once again, the less efficient shape presented to the oncoming air will lower the ballistic coefficient making the bullet lose velocity faster and more prone to drift or tumble.

If it happens at 25 yards I highly doubt it is from anything you did or didn't do. I would first check with the caliper then call a tech at Barnes. Even though they can't sell those bullets any longer, they should be more than willing to make it right and solve the problem.

Over-stabilization is highly over rated. It's not that. Wait see till he measures the bullets and gives a diameter.

I measured some of the bullets-

They seem to be .414 to .415, but that is the same as the TSX's that are not doing this.

I went out and shot some factory Trophy bonded solids, and they are tumbling at 100 yards too.

The rifle is a Dakota 76. I have not measured the twist rate- will do that later- and the crown looks good.

The gun shoots 1/2 to 3/4 inch groups with the TSX at 100.

I also made up some new loads and they are doing the same thing, but velocities were a little higher than I recall- the TSX's were doing 2500. The solids were 2450 and the Factory TBSS's were 2430.

Depending on YOUR rifles chamber and free bore, the bullets could be jumping into the rifling at the new higher velocity and "skidding" on top of the rifling. I have done this in 8mm Siamese and 50 Alaskan where the slower loading performed normally.
Another phenomenon is that the bullet is not entering the throat centered to the bore and engages the rifling at a slight angle. This too will cause abnormal engraving of the bullet and cause very poor accuracy/tumbling.
A good indication is if the bore is getting fouled with jacket material more than you remember.