215 Berger Hybrid help....

[lifesupport4u]

I am starting to work up a load with Berger 215 Hybrids in a 300win mag. I am loading to 2.785 CBTO and started at 75 grains of powder. I am realizing maybe I need to start lower on powder.

I'm using a Forster Ultra Micrometer die and have checked the seater stem and it's not bottoming out.

However with my Hornady comparator I am getting inconsistencies in CBTO of .005"

Not sure why I am running into this issue? Die was well secured

 

[dok7mm]

Even on the 215, a great bullet, the ogive will have variance that can cause a different measurement.

You might also being a bit inconsistent on the pressure you use, it doesn't take much. Or, your calipers may not be the highest quality.

I prefer to sort bullets with a stand and and dial indicator, as the spring pressure is very consistent. Also make sure the bullet is seated square in the comparator opening.

The simplest way is back your micrometer seater off a bit and seat all bullets with a consistent method. Then sort by cbto and screw down micrometer as needed to seat long bullets to same cbto.

 

[L.Sherm]

Squeaky clean necks and work hardened necks will make inconsistent CBTO also.

 

[lancetkenyon]

Make sure all primers are seated fully as well.
Neck tension is probably the culprit though, as L.Sherm stated.
Anneal your brass, and run them through a .306 expander mandrel.
I rarely find Berger bullets to have more than .001-.002" variance in BTO on their bullets. OAL can vary due to meplat variance, but I really never even measure that.

 

[Jud96]

I've never had CBTO vary more than 0.002 one way or another with Bergers. I also don't use the top shelf dies either. So as others said it's most likely your case necks. Do me a favor, measure the outside diameter of a sized case, and the outside diameter of a loaded round. The sized case should be .001-.003 under the diameter of the loaded round. Also, how does seating feel? Does every bullet seem to seat with the same feel, or do some feel looser or harder to seat than others?

 

[lifesupport4u]

I think it is a neck tension and/or neck cleanliness issue. It's new brass and I used a .333 bushing in a Type S bushing die WITHOUT the expander button. Maybe for first time firing I need to use the expander?

I sized some of the brass with an RCBS FL die and it seated much more consistently (CBTO within .001 which is probably just technique or my calipers). The neck tension on these rounds is .0015

I saw some reloading video from Panhandle Precision where he uses the Type S Bushing die without the expander but that may only be once fired brass?