Runout?!

[PEI Rob]

Try another bullet, unlikely the problem but a very quick check. If not, anneal the cases out of the rifle than prep them.

 

[CINOSBUS]

My best guess is that it's the bullets.

That's the 1 thing you've changed for sure and if they are a different size along the bearing surface from front to rear, that would explain it. Check them with a micrometer.

 

[Winchester 69]

...can you expound on this a bit? I honestly don't know, and have no way of knowing now if there was a change in bullet diameter, but how would this change runout numbers?

The inside chamfer of the cases influences the alignment during seating of the bullet with the case mouth. This alignment in turn influences the straightness of the finished load. Since you apparently no longer have any of the earlier batch of bullets, we can't compare diameters. What I am suggesting is that a larger diameter would influence alignment. Examine the inside chamfer of your brass. The most desirable configuration is for minimal outside deburr, and a long, low-angle inside chamfer. Experiment with allowing for more inside chamfer. If you're not using a low-angle tool, usually identified as "VLD", it may be worth pursuing if another cause for the excessive run-out isn't identified. The tools will have a 20 to 30 degree angle.
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[Forester]

OK, heres an overdue update...I do use a VLD chamfering tool so that was not the issue.

I went back and started at the beginning with some recently fired Lapua cases. With these I checked runout after every step in the process and found they had very little to none after they were fully prepped. When I seated a bullet in these cases I was back to my old, good, low runout numbers.

The only thing I changed was that the press and all dies involved got an extremely thorough cleanup. I did find some buildup under the universal shellholder base plate which could have forced the case to sit off square with the rest of the press.

I thought I had these things covered before but apparently this was more a case of "garbage in, garbage out" than any big mystery. I sure wish I had had the good sense to check the easy things first before I got into all the checking, measuring, and general hair pulling I went through.

Thanks to those who had some input on this. If something good came from it, at least I have been through my loading process pretty throughly now and looked at everything pretty closely for problems or potential problems.

 

[Cruizin]

Here is my input. I have a 338 edge ai and I have some loaded rounds that vary quite a bit. I use redding competion dies neck and bullet seater with no expander ball and, I neck turn and aneal cases but have many lots that I reload and not all are turned. I have to say that the neck turned cases have the least amount of runout but I believe the issue is in the bullet. Even the neck turned cases have issues but they do have better consistency, but it still leaves some to be desired. I am also using a forster press. I use sierra 300 smks and considering how much they vary in bearing surface (I've seen up to .015") I feel that a lot of the run out has to do with the consistency of the bullet itself.

How round is that darn thing? It's a lot of copper and soft lead. How much does the point where the press grabs the bullet to push it into the case vary from the centerline datum? In other words how much does the point of the bullet vary from the centerline?

Does anyone measure this with the sierra smks?

I have heard Berger has made some new dies/tooling and their BS varies very little from bullet to bullet (+or -.001 or less). I sure wish they would make some 338 cal so I could try them.

 

[Forester]

Here is my input. I have a 338 edge ai and I have some loaded rounds that vary quite a bit. I use redding competion dies neck and bullet seater with no expander ball and, I neck turn and aneal cases but have many lots that I reload and not all are turned. I have to say that the neck turned cases have the least amount of runout but I believe the issue is in the bullet. Even the neck turned cases have issues but they do have better consistency, but it still leaves some to be desired. I am also using a forster press. I use sierra 300 smks and considering how much they vary in bearing surface (I've seen up to .015") I feel that a lot of the run out has to do with the consistency of the bullet itself.

How round is that darn thing? It's a lot of copper and soft lead. How much does the point where the press grabs the bullet to push it into the case vary from the centerline datum? In other words how much does the point of the bullet vary from the centerline?

Does anyone measure this with the sierra smks?

I have heard Berger has made some new dies/tooling and their BS varies very little from bullet to bullet (+or -.001 or less). I sure wish they would make some 338 cal so I could try them.

I do not believe these Bergers came from the new tooling. I sorted them by BS length and they varied from .447"-.452" about 100 were at .449" and another 60 or so were in either .448" or .450". How does that variation compare to yours?

 

[Cruizin]

I have never used berger bullets but I am building a 7mm wsm right now so I can shoot the 180 grn 7mm bullets. I read a post from GoodGrouper where he mentioned that Berger was investing in new tooling. He received a shipment of them and was very pleased. Maybe he will chime in and fill us in on the bearing surfaces of the lot that he received.

All I know is that all my neck turned cases come out of the gun and are .0015 at that neck as far as run out goes. I neck size them and they are still the same, then I load them and some vary up to .006. I'm stumped.