Can a Lee Collet die be set to bump the shoulder?

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Tim L
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Can a Lee Collet die be set to bump the shoulder?

#1 Postby Tim L » Fri Jan 17, 2020 12:45 pm

The reason for the question is that mine seem to.
I generally shoot 308 but also had a custom die made for a 6.5 SLR. I drive both pretty hard but never seem to get case growth.
I'll admit that neither grow a measurable amount on a single firing but even after many they still chamber with no measurable increase in length.
The collet die does have a shoulder, and in order to close on the neck the shoulder of the collet must move down. Could it be bumping the shoulders?

jasmay
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Re: Can a Lee Collet die be set to bump the shoulder?

#2 Postby jasmay » Sat Jan 18, 2020 5:23 pm

One thing I have found is that “factory chambers” and “Custom Chambers” are as we know different beasts, much of the “brass flow” talk probably somewhat predates precision stuff of these days.

I certainly don’t see brass flow/growth in my custom rigs as I do in hunting riga.

Or, could just be that what you think is hard isn’t developing that much pressure.

pjifl
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Re: Can a Lee Collet die be set to bump the shoulder?

#3 Postby pjifl » Sat Jan 18, 2020 9:46 pm

Lee Collet dies do not snugly enclose the case walls - instead there is a small gap. In fact, the sliding collet angular internal top just under the neck may not even match the case shoulder angle. This is what makes them so useful for experimental cases.

I have found during my experiments to modify Lee Collet Dies that, if for some reason, the sliding collet part is too short and the 'shoulder' gets pushed down, there develops a bulge just under where the shoulder meets the case body is squeezed.

When modifying them, one normally starts with a sliding collet which is too long and shortens it by turning off some of its base. The opposite is possible but involves making a small spacing ring to effectively lengthen the collet so only the neck is being squeezed.

Because of this, I cannot see how one could 'bump back the shoulder' intentionally and reliably with a die of this type.

Many of the coarse dies pull lengthwise on a case as the internal plug is pulled out which adds to case 'growth'.

Peter Smith.

KHGS
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Re: Can a Lee Collet die be set to bump the shoulder?

#4 Postby KHGS » Sun Jan 19, 2020 3:39 pm

pjifl wrote:Lee Collet dies do not snugly enclose the case walls - instead there is a small gap. In fact, the sliding collet angular internal top just under the neck may not even match the case shoulder angle. This is what makes them so useful for experimental cases.

I have found during my experiments to modify Lee Collet Dies that, if for some reason, the sliding collet part is too short and the 'shoulder' gets pushed down, there develops a bulge just under where the shoulder meets the case body is squeezed.

When modifying them, one normally starts with a sliding collet which is too long and shortens it by turning off some of its base. The opposite is possible but involves making a small spacing ring to effectively lengthen the collet so only the neck is being squeezed.

Because of this, I cannot see how one could 'bump back the shoulder' intentionally and reliably with a die of this type.
Peter is quite correct.
Keith H.

Many of the coarse dies pull lengthwise on a case as the internal plug is pulled out which adds to case 'growth'.

Peter Smith.

argh
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Re: Can a Lee Collet die be set to bump the shoulder?

#5 Postby argh » Sun Jan 19, 2020 3:59 pm

Can some of you who are running collet dies do a check on if the shoulders are pushed back during sizing? Not just theorising?

I have checked previously with a hornady comparator and found a small amount of shoulder set back, and theorized that when the collet clamps down on the neck, the case is still pushing the case into the neck, and collapsing the shoulder partially - this would mean that the shoulder datum (0.4" dia on 308) was being pushed back, but not the entire shoulder.
I checked on my 308 cases today, with a new sinclair guage which matches the shoulder angle, and i got .002 to .005 shoulder setback.......
Repeated this about a dozen times. My collet die does not touch the shoulder either.

Can some others please check their results?
Cheers
Adrian

DannyS
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Re: Can a Lee Collet die be set to bump the shoulder?

#6 Postby DannyS » Sun Jan 19, 2020 6:57 pm

Adrian, I think Peter Smith and Keith Hills have answered the questioned and they aren’t just theorising.

Cheers
DannyS
You might as well be yourself, everyone else is already taken.

argh
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Re: Can a Lee Collet die be set to bump the shoulder?

#7 Postby argh » Sun Jan 19, 2020 7:57 pm

DannyS wrote:Adrian, I think Peter Smith and Keith Hills have answered the questioned and they aren’t just theorising.

Cheers
DannyS


Actually peter is talking about modified collet dies if the body part is cut down too far. Keith has agreed with Peters comments and said he cant see how you can reliabily and intentionally bump the shoulder.

I would like to know if its just my setup of the die, or just my die, and would like some others to check if they get any shoulder.... change. I wont call it "bumping" as its not consistent, and not intentional.

Tiger
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Re: Can a Lee Collet die be set to bump the shoulder?

#8 Postby Tiger » Sun Jan 19, 2020 9:35 pm

The question has been answered above, Lee collet dies do not bump the shoulder, again as has been said above, there is clearance around the shoulder in the interior of the collet intentionally to avoid touching the case shoulder.

If you are having problems with the collet touching your shoulder you may be using a shortened shell holder with the collet die, this will remove the intentional clearance and push the case further into the die possibly causing a bulge in the shoulder, probably resulting in cases which will not chamber.

Always use an unmodified shell holder with the collet die if you are having problems. I have had this problem in the past.

Cheers.

Dave.

Rich4
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Re: Can a Lee Collet die be set to bump the shoulder?

#9 Postby Rich4 » Sun Jan 19, 2020 10:58 pm

Run a test by placing a washer on your shell holder over the case and check the datum measurements for both ways, it won’t matter what anyone else is getting, only your own results
Rich

argh
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Re: Can a Lee Collet die be set to bump the shoulder?

#10 Postby argh » Mon Jan 20, 2020 5:45 am

Rich4 wrote:Run a test by placing a washer on your shell holder over the case and check the datum measurements for both ways, it won’t matter what anyone else is getting, only your own results
Rich

Hi Rich, i can confirm that the shoulder of my case does not touch the shoulder portion of the collet. Checked and double checked. I would never normally check headspace, or base to shoulder datum, when neck sizing, but a while ago i did check and saw that it was making a change.
Interested if anyone else had this (on unmodified collet die) ?
Its not consistent, and i still use a redding body die every 3 to 5 loads to size the body back down and ensure easy chambering.
Cheers
Adrian

pjifl
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Re: Can a Lee Collet die be set to bump the shoulder?

#11 Postby pjifl » Mon Jan 20, 2020 7:49 am

Perhaps this may be interesting.

I still have a box of 100 cases with severely turned down necks but no barrel of mine is chambered for these any more. I just cannot bear to throw them away. Recently I decided to shoot some and just accept that the necks would give up and develop cracks and expire.

To reload them, I used a collet die - the original die setup for those reduced necks - well I cannot find it anymore.

The Lee Collet die that I had modified would slightly bulge the shoulder diameter on these thinner neck cases but not on standard necks. It took me a while to decide it was not my imagination - it was really happening. It was enough to stop chambering the round but hard to see without careful measurement.

Eventually, I decided that as the collet claws closed further on the thinner necks, the length of the collet effectively shortened as the cone entered the collet closer a little further.

This raises the possibility that a collet of almost perfect length for the case may just be bumping some of the shoulder but I consider this to be counterproductive. The whole point of a collet die is that it may be made to loose tolerances, but, because of sensible geometrical design, gives excellent and consistent resized necks.

As an aside. these thinner necks have been shot 3 times now in a larger neck chamber. Quite accurately, and with no split necks yet. Not to be recommended but maybe it says something about the fad of neck turning !

Peter Smith.


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