Head spacing

[dolek]

But the important part is the size of your chamber, the bit where your resized brass has to fit. That doesnt change. So if your die is set to bump the shoulder of your brass back a certain distance from the chamber size, it should never have to change until you rechamber or rebarrel.

Btw, i use 3 different brass brands in my 308 and only lapua in my dasher, but for each barrel/chamber i set my dies up and dont ever need to change. I dont see any difference in ease/difficulty in chambering those rounds, and i certainly dont waste my time at the loading bench check measuring every round, or even one in 10 rounds.....

Spring back...plain and simple.

 

[dolek]

 

[Ned Ludd]

I guess youve never measured brass over time. You bump it .002 this firing and 2 firings later that same setting may only bump .001 on some. But your mileage may vary

I guess it might if it wasn't annealed properly, but that's not the fault of the die/lock ring setting. I measure brass every time it is prepped, both before and after the re-sizing step, and I have not observed the issue you're describing.

 

[mike a]

No way you folks have been measuring your brass correctly if you lock down your dies down .

Don't leave us hangin

 

[Uncle Ed]

I guess it might if it wasn't annealed properly, but that's not the fault of the die/lock ring setting. I measure brass every time it is prepped, both before and after the re-sizing step, and I have not observed the issue you're describing.

I take it you never bought once fired Lake City 7.62 cases and seen machine gun fired brass spring back.

 

[Metal God]

I guess youve never measured brass over time. You bump it .002 this firing and 2 firings later that same setting may only bump .001 on some. But your mileage may vary

The thing that changes in the brass is it's work hardening over time causing more resistance to sizing . That said , all presses have what's called flex or deflection when a load is put on them like sizing a case .

EXAMPLE : here are two photos , 1st with the ram fully up and the die and shell holder making light contact with NO case in the die . 2nd is the ram fully up when sizing a case with out touching the die's adjustment .

Note how now that there is a load on the press there is a gap in between the die and shell holder . This is the deflection/flex I'm talking about . When your case resist sizing do to work hardening it causes your press to flex a little more . Remember we are talking .001 to .002 difference , the load does not need to be that much different to cause that variance . You need your press to over come this extra load being put on it .

The way to do that is have you die and shell holder make firm/hard contact at the top of the stroke . That's where the competition shell holders come is and shine . They allow you to have that firm/ hard contact all while sizing your cases longer in .002 increments .

Did the lightbulb finally go on ?

 

[JMayo]

I think the base get thinner with a bunch of firings ... My old brass has somewhere around 30 firings on it now. I have to change pma settings for it.

 

[cw308]

When measuring CBTO I guess you could lock down your die but CBT Datum brass is changing in different ways with every firing , small changes but change enough to need die adjustments if your looking for accuracy.

 

[Texas10]

In my experience if I'm not using the exact same shell holder with a particular die, there may be some variance in headspace not necessarily due to spring back, but rather due to manufacturing variance in the shell holder.

I'm remember seeing shims advertised or mentioned for shell holders made specifically for this issue. If anyone has a link, I'd very much appreciate it.

 

[cw308]

I see what going on with Metal , my cases size with very little effort , probably because I'm shooting mild loads , some have used a feeler gage instead of shims to remove the slack .

 

[Uncle Ed]

Using Skips shims under the lock ring requires removing the die for every headspace change.

With the Redding competition shell holders all you do is change shell holders and never touch the sizing die.

I prefer using the Redding shell holders and pausing at the top of the ram stroke to reduce brass spring back.

 

[Metal God]

I used feeler gauges for a little while but they slowed me down . If you're using them between the die and shell holder to set head clearance . Is there always that .007 gap allowing for that flex in the press or do you keep the feeler gauge in between the die and shell holder on every case you size to allow for cam over or hard stop depending on the press ?

IMHO if you're not removing the press flex/deflection you will not get consistently sized cases from CHTD . I'm not exaggerating on my +/- .0005 variance CBTD measurement . The comp shell holders are crazy good when used correctly . \

It's ok guys I fought excepting them for a couple years and thought the feeler gauges and shims were better , I was wrong !

 

[Dusty Stevens]

What are you using to measure to the .0005 repeatedly? It takes a skilled machinist and good mics to read that.

 

[cw308]

Dusty
When it comes to .0005 something that small would it make a difference . In looking at a space of .001its really nothing . When sizing a case with .001 head clearance it seems pretty simple , but when you really think of such a minor change can change things so much. Good thing homes aren't built that way. I think the mirror is .005 too high on one side

 

[Metal God]

What are you using to measure to the .0005 repeatedly? It takes a skilled machinist and good mics to read that.

Just my calipers and a comparator ( yes I know ) but all 350 cases I just sized which were once fired LC-15 measured 1.6215 or 1.6220 from an avg of 1.6270 before sizing . I understand your point fully . Just keep in mind that any variance you think my tools may not be showing .Yours are doing the same but your ES is +/- .001 or more if your not removing the flex in your press . So if you think I'm likely only getting +/- .001 at best you are doing even worse lol because your tools aren't likely doing any better .

This is a "theory" that is easily tested by anyone . If you want to test the flex issue then do an honest test by sizing 10 cases with the die and any shell hold making firm contact with cam over . Then 10 cases that leave a gap like in my pic . Then measure each set of 10 CBTD and see which has a more consistent measurement .

 

[Metal God]

Good thing homes aren't built that way. I think the mirror is .005 too high on one side

Yeah every time I look at my self It feels like I'm standing on a hill LMAO

I crack me up

 

[Metal God]

It’s not that it makes a difference, it’s simply pointing out how well the comp shellholders work and how easy they are to use .

Wow when some of you sink your teeth in you just can’t let go can you .

 

[Metal God]

I'll post the video again showing how they work . His die is already set . There is no adjusting the die , spacing it with any type of gauge , seting the lock ring , or locking the lock ring with and allen nut . Just a quick change of the shell holder until he gets the right one .

 

[cw308]

J
Using the feeler gauge or Shellholders , it works . All we are doing is passing out helpful information .

 

[Texas10]

I'll post the video again showing how they work . His die is already set . There is no adjusting the die , spacing it with any type of gauge , seting the lock ring , or locking the lock ring with and allen nut . Just a quick change of the shell holder until he gets the right one .

Will someone please explain to me what the video is leaving out? He set the die to firm contact with the shell holder and doesn't get enough shoulder bump. Then changes shell holders without changing contact with the die.

What part of the competition shell holder is being machined to a different dimension to allow the brass to go further into the die? Is it the distance between the shell platform and the base (point of contact between the ram and the shell holder) ?. And how does this differ from placing say, a .002 shim between the shell holder and ram?

Inquiring minds would like to know.