How much neck expansion?

H

hedditch

Guest
Art, from your last post, Subject: Neck turning the 6 PPC, you indicated, if I read it right, .0005 to .001 is needed for neck expansion. I am not doubting your figures but I am requesting other's to resond with their actual experiences on how much room is needed for case neck expansion for an un-incumbered exit of the bullet? What nuances may effect the determination of this figure other than the differences in diameter of the pressure rings of differrent makes of bullets and the manufacuring tolerances of the brass as Art has already mention?
Dave
 
I didn't see Art's writing of this, so I'm unsure of the context of it.
Was Art talking about expansion to proper turning mandrel fit, or neck clearance?
 
Art was talking about the necessary clearance required for the brass to expand to allow the bullet to exit the neck of the brass without interference from the neck of the chamber when one pulls the trigger. in other words, what would the maximum diameter of the brass with bullet to safely allow the exit of the bullet with a .267 neck in a 6 PPC? .265? .2655? .266? .2665?
Dave
 
Never heard of one clearance amounting to better than another, outside of excessive for consistent tension after all the sizing.
Any clearance from +zero on up works..
I've fitted necks to 0.001 under chamber neck without issue. With this I never needed to neck size at all. In fact, the entire cartridge to chamber was this tight, and the only sizing in ~30 reloads was light bumping.
 
Dave ...

hedditch said:
Art, from your last post, Subject: Neck turning the 6 PPC, you indicated, if I read it right, .0005 to .001 is needed for neck expansion. Dave
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Some where in the range of .001" to .002" is need for a safe release of the bullet.

The figures you quoted above [.0005" to .001"] would be a range on ONE side of the case to chamber dimension. There are TWO sides don't forget.

It's usually referred to as a total of from .001" to .002". Meaning .0005" on one side of the neck + .0005" on the other side of the neck which equals .001" total, or .001" on one side of the neck + .001" on the other side of the neck for a total of .002" [which apparently is becoming more the norm these days].

Or, in my case, .00075" + .00075" = .0015". With my .2620 chamber, I'm looking for a .2605" loaded round. .2605" + .0015" [of total voided space/half on each side] = .2620

Years ago some individuals loaded what was know as a "fitted neck" which was a very scary .00025" + .00025" for a total of .0005". The neck brass plus seated bullet needs room to release the bullet safely. .0005" total to me was tempting fate. Measuring consistently to the 4th decimal place or to 1/10,000th of an inch is tricky business. That 5th place up there is 1/100,000th!

I measure the [easy] way that Jackie Schmidt taught me. I don't turn necks to a certain dimension. I keep taking brass off a little at a time, seat a bullet and then measure the total and then keep doing that until I get the .2605" that I'm looking for. In the end that's all that matters. It may seem a little tedious but once you've got your turner set to give you what you want you're done. I also measure about every 5th round as a Quality Control check to ensure everything is proceeding as planned.

I hope all this makes sense. :)
 
hedditch said:
What would the maximum diameter of the brass with bullet to safely allow the exit of the bullet with a .267 neck in a 6 PPC? .265? .2655? .266? .2665?
Dave
Click to expand...

If you could ensure that the loaded round with seated bullet was always .2650 for a .2670 neck chamber you'd always be safe. You would have .001" clearance on each side. Which is what I said above is becomming more of the norm or said another way, the default setting.
 
Art, It all makes perfect sense. Thank you!
Mikecr, I wasn't quite sure what you meant. Are we discussing the same thing, safe release of the bullet (as Art put it)?
Dave
 
You can get by with less clearance, but the closer you get to the edge of the cliff, the greater chance you have of any slight build-up of crud or slight deviation in a piece of brass causing you a problem. If it weren't for the "we don't live in a perfect world" thing, we could cut the amount of clearance needed to a tiny amount. The question becomes, "how lucky do you feel" or, "is there dust where you shoot"?
 
hedditch said:
Mikecr, I wasn't quite sure what you meant. Are we discussing the same thing, safe release of the bullet (as Art put it)?
Click to expand...
I know what you mean, but there is no correct answer other than 'enough'.
Clearance for one of my guns is .001 as stated(.0005 per side), and my pressures, velocities, and ES are excellent. Then again, I measure my stuff and take care of my chamber/gun.
Also, the throat on this gun is coaxial and .0005 over bullet dia(.00025 per side).
So I've provided one extreme example I guess..
 
abintx said:
Some where in the range of .001" to .002" is need for a safe release of the bullet.
Click to expand...


I sure wish some a' you'se would TEST this stuff before parroting it all over.

This is BRC, not Rollicking und't Yakking arounde Ye Jollie Kempfire.

How could "too little clearance" be dangerous? I've run clear down to scuff-fit with no signs of pressure.

Yes, this liddle tidbit of information gets passed on as "truth" all the time but I've YET to find one person who can even anecdotally relate a story showing the "danger."

I'm not advocating slip fit, I'm just not seeing it as a safety issue. CRIMPING from too-long brass is a safety issue, but if you can close the bolt without resistance, you're golden diametrically.......

al-SafetyGeek-inwa


waiting
 
testing tight necks


i know of a fellow that lives about 5 miles away that once run a test on tight necks. he actually loaded a 6.5 bullet in a 25-06 with no ill effects. for one shot anyway.
 
Al ...

alinwa said:
How could "too little clearance" be dangerous? I've run clear down to scuff-fit with no signs of pressure. alinwa
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Someone let Al out again! Who was it? :D

How come this cutting-edge advice, :rolleyes: wasn't included here: THE BOOK OF RIFLE ACCURACY by Tony Boyer, Chapter 13: cases, page 139?

Shoot Safe. :)
 
I'm with Al
It's common to jam bullets into the lands, and to fully engrave on firing -from jammed(no run at it), surely takes higher forces than that of bullet seating into/from necks.
Now if you don't measure your stuff, and work up stiff loads with one lot of brass, only to mix lots later, again without measuring, and your not bumping correctly, so you're used to heeling your bolt closed on mixed lot rounds, You might get a surprising pressure sign one day.. Ya think?

But if all is just opposite(as it should be), it's just not an issue.
Does it make a argument to go very tight fit? Probably not. But it doesn't negate it either.
 
abintx said:
Someone let Al out again! Who was it? :D

How come this cutting-edge advice, :rolleyes: wasn't included here: THE BOOK OF RIFLE ACCURACY by Tony Boyer, Chapter 13: cases, page 139?

Shoot Safe. :)
Click to expand...

Well, since't you seem to think use by HOFers is validation, I got the term "scuff-fit" from the man closest to Tony Boyer in the HOF. #2 in "da' book"..........he used it for a special project, he used the term, I tried it. I hold this man in very high regard re case/cartridge/bullet design.

My very first post on this BRC board was on this subject. I titled it "does the bullet obdurate in the neck?"

Long story, many laffs, suffice it to say that my reception here was .......... varied.

As is my tenure.

al
 
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