Variation in Bullet seating?

[Kadams1563]

6.5 Creedmoor
Virgin Lapua brass
140 eld-m
Redding seating die with .289 bushing

I am loading at 2.200 Base To Ogive and measuring with the Hornady tool and a set of Mitutoyo calipers.

I loaded 25 rounds and 6 of them were short at 1.195-1.198.

How much variation is acceptable and is this normal?

What is causing the variations?
The bullets, brass, dies?

I did notice the ones who seated short seemed to set really easy. So maybe the necks are out of wack on the brass?

Or I thought the bullets might be fluctuating.

Last question when loading and you get a short or long round abnormally do you go back and pull the bullet and seat to the correct length by adjusting the die to get the perfect CBTO?


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[Supersubes]

Neck tension could have something to do with it. The more resistance the neck provides, the further into the seating stem the the bullet will go. Did you chamfer the necks, or rely on the lapua chamfer? Speaking of the seating stem, have you confirmed that the bullet tips arent bottoming out in it? When im seating, I pause at the bottom of the stroke mometarily, which helps with small variations. I would shoot them, instead of pulling/reseating the short ones. Good opportunity to test the variation on target though.

 

[flyright]

That's not completely abnormal. I've found as much as .007 variance in the 140 ELDM ogives. For a while I sorted them into 3 groups - longest, shortest and the middle range. I did not see much, if any, improvement on paper so I gave that up. The first ELD's I used were very consistent but not so much now. Maybe the tooling is getting worn now. The newer 147's are extremely consistent sooo...

 

[CharlieNC]

If you feel associated differences in seating force its time to anneal to restore uniform neck tension.

 

[918v]

6.5 Creedmoor
Virgin Lapua brass

 

[mdmp5]

Are you setting the seating die once and seating everything?

 

[lash]

I think you provided your own insight in the first post. As mentioned neck tension and I.D. Chamfer are important if you want pretty consistent base to ogive dimensions.

So, while prepping brass, ensure that you are getting consistent neck inside diameter. How you choose to do that I don't care. Different people get there using different methods, but without some way to measure and control neck I.D. before bullet seating, you will get inconsistent seating.

Then make sure that you regularly chamfer the ID of the case neck. I happen to like a light chamfer every time I prep.

Then make sure you are using a consistent measurement method. Try measuring the same item three or four different times and see if you get variable readings and if so, by how much. It's called gage R&R.

Finally, I'm willing to bet that the variation you are seeing will not be noticed when fired, IF you have a well developed load. With the exception that variations in neck tension can and will affect your ES and SD.

 

[Kadams1563]

I chamfered the necks using a vld tool.

I also have no idea if the bullets are bottoming out. I never knew Redding made a VLD style Bullet stem to replace the regular seating stem.

Well anyways my load testing didn't go well today. That all shot worse then my unprepped Hornady brass even though the SD's and ES were way lower. Getting frustrating lol.

And I would adjust the seating die every time trying to get the perfect CBTO for my load testing.


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