Case Tension Again

[918v]

Imagine the following:

A hollow-point bullet with a thin jacket and a soft lead core, like the Hornady XTP.

A Redding Competition Seater with a conical interior profile seater plug.

A group of cases with various degrees of case tension.

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As the bullet is being seated, the seater plug exerts pressure on the sides of the bullet nose, not on the bullet tip. The case, on the other hand, exerts pressure on the sides of the bullet shank.

The greater the case tension, the higher the seating pressure.

What happens to the bullet nose? I have personally observed the hollow point of a hornady XTP change in appearance after having been seated. In every case, the hollow point was reduced in diameter, some more than others. The reason for this is two fold: The conical seater plug exerted force on the sides of the bullet nose, so as the bullet was being seated, the bullet nose swaged into the seater plug, assuming the profile of the plug's interior. The other cause is case tension variance. Some cases caused an increase in seating pressure, which in turn caused the bullet to swage deeper into the seater plug.

Why is 918v babbling about this crap?

Because 918v does not need a strain gauge! All 918v needs is to seat all the bullets with a the competition seater, and then sort by OAL. The longer the OAL, the greater the seating pressure must have been.

Problem solved?

[Steve Koski]

Throw that range crap away.


Just start with new Starline brass each time. I heard somewhere that helps.

[918v]

I just tried this with the competition seater:

The resulting OAL ranged from 1.097" to 1.104". Sure as ****, the cases with the lightest tension (as determined by feel when running them through the expander die) resulted in the shortest OAL, and the cases with the heaviest tension resulted in the longest OAL.

So the range is .007"

Most fall within 1.102" +/- .001"

I think I just may abandon weight sorting in favor of OAL sorting. It's gotta be one or the other, otherwise I won't have enough brass to play with.

[AdamN]

All you can do is try it,

What equipment do youi load with?? Have you considered trying the expander off of a 1050?? Its not caliber specific and only has an straight angle cut on it. It ony flares/bells the case and does not "expand" like on other equipment.

I hadnt considered it before but Ive had some very good shooters tell me that it increases the neck tension and improves the shot to shot consistency.

BS???? I dont know.

[918v]

I have a Lee universal expander that works just like the Dillon, but I'm presently using a RCBS expander, reason being that it allows me to feel case tension.

But if I'm gonna sort by OAL, I might as well go back to the Lee and increase tension a bit.

I'll test it several ways:

One batch will consist of rounds sorted by plug gauges. Another will be sorted by OAL. I'm pretty sure the two methods will yield similar results.

[Tree Rat]

I have a Lee universal expander that works just like the Dillon, but I'm presently using a RCBS expander, reason being that it allows me to feel case tension.

But if I'm gonna sort by OAL, I might as well go back to the Lee and increase tension a bit.



How does the RCBS expander provide better feel when expanding over the others?

How does the Lee expander provide more tension over the RCBS?

Are both the RCBS and Lee expanders drop in's to the Dillon powder die?


TR

[918v]

The RCBS expander actually expands the case a bit.

The Lee only flares the case mouth. It does not expand the body.

Neither allows powder to flow through.

[Tree Rat]

What operation step do you use either in?


TR

[918v]

In the case expanding operation, you know, the one that follows the sizing operation and precedes the powder charging operation.