Runout opened up when I switched bullets

[RmeJu]

I'm loading on a Forster Co-ax, using a Forester ultra micrometer seater.

I recently switched from 7mm Hornady 162gr ELD-M to Berger 184gr F-open. With the Hornadys, I was consistently getting 0.5 to 1.5 thousandths runout. With the Bergers, I'm getting 2 to 4 thousandths.

The Bergers are longer, so I thought they might be bottoming out in the die, but (1) I'm not getting inconsistent CBTO measurements, which I would expect if I was bottoming out, and (2) I opened up the die and placed a bullet in the seater, and didn't see any obvious bottom out... although I admit that if it was just *barely* bottoming out, it'd be hard to tell.

Any ideas of why my runout is opening up?

 

[spife7980]

I’d be curious if raising the die body itself up a revolution in the lock ring as a way to accommodate the extra length would fix it. Is the case sleeve bottoming out?

 

[RmeJu]

I’d be curious if raising the die body itself up a revolution in the lock ring as a way to accommodate the extra length would fix it. Is the case sleeve bottoming out?

I don't know, but I will check that and give it a try!

 

[Supersubes]

Any chance the bullet tip is bottoming out in the seater stem?

 

[Wheres-Waldo]

I had the same issue when switching from Matchkings to Hybrids.

Take the stem out, put it in a drill chuck, lathe, whatever. Grab a Berger and put some lapping compound or the like on it and burnish/lapp the two together.

This will change your micrometer setting on your die, so have a loaded round you can screw the stem back down on to get your old seating depth back.

It didn’t move my loads into the .0005” range, but better than .004” on average.

 

[Rhed]

I'm loading on a Forster Co-ax, using a Forester ultra micrometer seater.

I recently switched from 7mm Hornady 162gr ELD-M to Berger 184gr F-open. With the Hornadys, I was consistently getting 0.5 to 1.5 thousandths runout. With the Bergers, I'm getting 2 to 4 thousandths.

The Bergers are longer, so I thought they might be bottoming out in the die, but (1) I'm not getting inconsistent CBTO measurements, which I would expect if I was bottoming out, and (2) I opened up the die and placed a bullet in the seater, and didn't see any obvious bottom out... although I admit that if it was just *barely* bottoming out, it'd be hard to tell.

Any ideas of why my runout is opening up?

Is it a crushed load since it’s a heavier bullet?

 

[RmeJu]

I’d be curious if raising the die body itself up a revolution in the lock ring as a way to accommodate the extra length would fix it. Is the case sleeve bottoming out?

The sleeve is not bottoming out. The first pic is an empty piece of brass, and the second one I lifted up the sleeve as far as it would go with a mini-flathead screwdriver.

Should I screw the die body in until the sleeve does bottom out? Or should I try backing it off as you suggested in your earlier post?

 

[RmeJu]

Take the stem out, put it in a drill chuck, lathe, whatever. Grab a Berger and put some lapping compound or the like on it and burnish/lapp the two together.

I will try this if the other suggestions don't work, or maybe to eek out a little better performance even if they do. I think it's a great idea, thanks!

 

[RmeJu]

Is it a crushed load since it’s a heavier bullet?

I don't think so. I'm working up some first loads with N570. I started with the lighter charges, so I don't think they're getting crushed yet, although to be fair, I don't actually know.

For reference, I'm working up 10 groups of 5, starting at 69.1 to 70.9, going in 0.2 grain increments of N570. I was having the most runout trouble with the lightest loads.

 

[Supersubes]

View attachment 7143649View attachment 7143648

The sleeve is not bottoming out. The first pic is an empty piece of brass, and the second one I lifted up the sleeve as far as it would go with a mini-flathead screwdriver.

Should I screw the die body in until the sleeve does bottom out? Or should I try backing it off as you suggested in your earlier post?

No, don’t bottom it out. It’s set up fine now.

 

[Rhed]

I don't think so. I'm working up some first loads with N570. I started with the lighter charges, so I don't think they're getting crushed yet, although to be fair, I don't actually know.

For reference, I'm working up 10 groups of 5, starting at 69.1 to 70.9, going in 0.2 grain increments of N570. I was having the most runout trouble with the lightest loads.

Most time can actually tell if it’s a crushed load by hearing. Or even with some press can kinda feel it. Anyways, try making a dummy round and see if you’re still having runout. Crushed loads most times throws off the seatings. And that causes run outs.

 

[spife7980]

View attachment 7143649View attachment 7143648

The sleeve is not bottoming out. The first pic is an empty piece of brass, and the second one I lifted up the sleeve as far as it would go with a mini-flathead screwdriver.

Should I screw the die body in until the sleeve does bottom out? Or should I try backing it off as you suggested in your earlier post?

No, you don’t want the sleeve all the way compressed. You’re supposed to be at least a full turn out from bottoming the sleeve out. I have better luck a bit further out than that even.