MEASURING HEAD CLEARANCE WITH PLASTIGAGE

[82boy]

Why would the primer have anything to do with this? You are measuring with a fired, and SIZED case.
primer knocked out.

Because anyone who reloads will have a spent primer and hopefully a set of vernier calipers to measure head clearance.


Again, WHY WOULD THE PRIMER HAVE ANYTHING TO DO WITH MEASURING HEADSPACE. IF THE CASE HAS BEEN SIZED (Either neck or fl.)THE PRIMER WILL HAVE BEEN KNOCKED OUT OF THE CASE BY THE DEPRIMING PIN, AND THEREFORE IT WILL NOT EVEN BE THERE, to add the primer again has absolutly NOTHING to do with headspace.

[bigedp51]

What does scotch tape have to do with headspace?

What does plastigage have to do with headspace?

Why do people use a fired resized case for checking headspace when the average resizing die makes the case .002 shorter than GO or minimum headspace.

On a rimmed case you can measure your rim thickness and add the primer protrusion to get actual headspace.

Using the primer method you are finding out how much "air space" is between the bolt face and the rear of the case and this is called head clearance. Head clearance or the "air space" is how much too short your cartridge headspace is from your actual rifles headspace from the bolt face to the datum point in the chamber.

With just a GO gauge, a Hornady cartridge headspace gauge and the spent primer method you can get your actual headspace reading "without" buying the second NO-GO gauge. (all your looking for is "how much" air space you have behind your cases)

http://i122.photobucket.com/albums/o254/bigedp51/IMG_1243.jpg

All a headspace gauge tells you is if the bolt closes or not, with a little creativity and other gauges you can find out your actual headspace reading.

The alternative is to buy headspace gauges in .001 increments to find your chambers actual headspace reading. (within .001)

http://i122.photobucket.com/albums/o254/bigedp51/308-762gaugesjpg.jpg

When you understand that the word headspace doesn't cause casehead seperations BUT head clearance does you will understand what I'm saying.

http://i122.photobucket.com/albums/o254/bigedp51/308failA.jpg

The whole point of this plastigage posting is how to be a cheap ba$tard and not buy headspace gauges, I'm trying to show another cheap ba$tard way of doing things.

[82boy]

On a rimmed case you can measure your rim thickness and add the primer protrusion to get actual headspace.

Lets see, how many Savage 10/110 rifles have a rimmed case.

[bigedp51]

On a rimmed case you can measure your rim thickness and add the primer protrusion to get actual headspace.

Lets see, how many Savage 10/110 rifles have a rimmed case.


When you can unscrew an Enfield bolt head in seconds and change your rifles headspace you tend to learn a little about headspace and head clearance and their effects.

There are many ways to skin a cat, if you do not like the methods I posted here then do not use them.

This is also an open forum and I do see a reason for the moderator to start a pissing contest over how to measure headspace. My postings here are not about egos or turf wars, they are about measuring headspace and head clearance and I do not understand your anger or attitude over the "air space" behind a chambered cartridge.

If you like we can talk about the "air space" in front of the shoulder and behind the rim if you wish to go deeper into the subject. ::)

http://i122.photobucket.com/albums/o254/bigedp51/762-30-06.jpg

Please notice the amount the primer is protruding behind the center case is "head clearance" and the half inch of "air space" in front of the case ment nothing. :o

[82boy]

When you can unscrew an Enfield bolt head in seconds and change ...

I thought this was a Savage web site. Who the heck cares about an Enfield.

[joeb33050]

I was measuring head clearance, primer protrusion method, with fired cases. As I walked on my continual search for thinness this morning, I realized I was wrong, and should be using FL sized cases to measure. I sized them and measured again. Samples of 10.
Fired cases, case length avg 2.0348", head clearance avg .0016"
FL sized cases, case length avg 2.0416", head clearance avg .0010"

The cases grew .0058" and head clearance with FL sized cases went down 6 tenths. I knew cases lengthened on sizing, but didn't know they lengthened that much. I would have bet that head clearance would increase-I would have been wrong.
I also don't seem to be any thinner.
joe b.

[bigedp51]

When you can unscrew an Enfield bolt head in seconds and change ...

I thought this was a Savage web site. Who the heck cares about an Enfield.


You are correct this is a Savage web site and Savage made more Enfield rifles than any other country during WWII. You can unscrew the bolt head and change headspace or loosen the barrel nut and change headspace. The two key words are headspace and head clearance.

Do I get punished in this forum because I only own two Stevens 200 rifles and they don't have the "magic" name Savage?

Or would you like to talk about beer and excess headspace and drop the attitude. ;)

http://i122.photobucket.com/albums/o254/bigedp51/10_foambeer_lgl.jpg

[bigedp51]

I was measuring head clearance, primer protrusion method, with fired cases. As I walked on my continual search for thinness this morning, I realized I was wrong, and should be using FL sized cases to measure. I sized them and measured again. Samples of 10.
Fired cases, case length avg 2.0348", head clearance avg .0016"
FL sized cases, case length avg 2.0416", head clearance avg .0010"

The cases grew .0058" and head clearance with FL sized cases went down 6 tenths. I knew cases lengthened on sizing, but didn't know they lengthened that much. I would have bet that head clearance would increase-I would have been wrong.
I also don't seem to be any thinner.
joe b.



Skinning the cat

http://i122.photobucket.com/albums/o254/bigedp51/IMGP5130-1.jpg

And controlling head clearance

http://i122.photobucket.com/albums/o254/bigedp51/IMGP4385.jpg

The shims control how far the die pushes the shoulder back and thus controls your head clearance. ;)

http://i122.photobucket.com/albums/o254/bigedp51/7-17-201054719PM.jpg

[joeb33050]

Does the micrometer device measure the cartridge headspace?
The shims allow precise setting of the die in the press to get repeatable non-standard die cartridge headspace dimensions. There are sets of shell holders that do the same thing. All cartridge headspace dimensions set with the these shims or shell holders are LARGER than using the die set at a dead stop in the press.
I can see that this is of use with a long headspaced gun, or a set of dies out of spec. I don't understand why they are used with a Savage gun with adjustable headspace.
I think that a correct die set/shell holder, correctly used, will size a case so that it will go in any correctly chambered gun. Less the .004" 30-06 interference, for example.
What am I missing?
Thanks;
joe b.

[ellobo]

It seems to me that apples and oranges are being discussed. Everyone is so wrapped up in the Apple method that they cant figure out the orages part. Headspce and head clearance are two different but related things. I think I have grasped the concept of the two. If you use a go gage that is to SAMMI specs for a given cartridge that is fine. But that does not guarantee that your new case or unfired case will be to SAMMI specs, nor will your resized case. Tolerances are part of any mechanical assy. I am willing to bet very few cases have thier shoulders in perfect contact with the chamber on a given rifle. The protruding primer method will tell you just how far your headspace really is not matching your case. The more mismatch the lower your case life will be and you will get fewer loads due to case head separation. Anyway, that is how I am reading all this. Simply put, your gage properly used will set the chamber to its proper place but new or sized cases may not match. The length of the lugs on the bolt head will vary and may give excessive clearance between the bolt head and the cartridge. Correct me if I am wrong on that but looking at the design it seems that it can happen. My 2 cents worth.

El Lobo

[bigedp51]

You have plus and minus manufacturing tolerances for your chamber, reloading dies, and cartridge cases.

If you set your headspace too tight you run the risk of your sizing dies not pushing the shoulder of the case back far enough and your resized case might not even fit YOUR chamber.

If your rifle has its headspace set long and you have a tight resizing die you can over resize your cases and have short case life and possible case head separations.

On average American made cartridge cases run on the small side BUT manufacturing tolerances allow for .308 cartridge case headspace as an example to be .004 longer than minimum "rifle" headspace when its on the plus side and .007 smaller cartridge headspace than than minimum rifle headspace.

Below from SAAMI .308 drawing for rifle and cartridge headspace length

Rifle minimum headspace or GO 1.630 (1.640 maximum)

Cartridge manufacturing headspace tolerances
1.634 to 1.627

How far your case stretches on the first firing has the bigest effect on case life when reloading followed by how far you push the shoulder back each time you resize your case.

On new cases I have had as much as .011 head clearance, therefore proper fireforming is needed to prevent case stretching in the base web area.

At a bare minimum you need a GO gauge to set your rifles headspace and a good method of measuring head clearance.

http://i122.photobucket.com/albums/o254/bigedp51/IMG_1243.jpg

http://i122.photobucket.com/albums/o254/bigedp51/rimless.jpg

http://i122.photobucket.com/albums/o254/bigedp51/308-bjpg.jpg

http://i122.photobucket.com/albums/o254/bigedp51/308-ajpg.jpg

[joeb33050]

This is my try, pictures may not work

HEADSPACE, HEAD CLEARANCE AND CASE SIZING

We start with any bolt gun, FL die set and shell holder.

Put the press ram all the way up, turn the die in until it touches the shell holder, lower the ram and turn the die in a full turn. The shell holder will now come to a dead stop on the die bottom, with no "over center" handle movement.
Writers say that with the die set this way, case headspace will be .002" (one writer) or .005" (another writer) less than GO-GAUGE dimensions.
I can't confirm this. Certainly it will vary with die and shell holder tolerances and press springiness. Cartridge headspace can be measured with this tool, an RCBS "Peecision Mic" micrometer.



308 Win GO gauge headspace dimension is 1.630", NO GO gauge headspace dimension is 1.634"; cited here http://www.6mmbr.com/308win.html .

308 WINCHESTER HEADSPACE SAAMI DRAWING
CHAMBER 1.630"-1.640"
CARTRIDGE 1.634"-.007"
OR
1.627"-1.634"

If a FL die set up as above makes cartridge headspace .005" less than GO gauge dimension, this would be 1.630" - .005" = 1.625" or .002" less than SAAMI minimum cartridge headspace dimension of 1.627".

As the difference between gun headspace and cartridge headspace increases, brass stretches more and must be (if FL sized) sized down more and case life decreases.

A case sized to 1.630" headspace, for example, will stretch less when fired in a gun with 1.634" headspace than in a gun with 1.640" headspace.

The ideal situation seems to be where cartridges (fairly) easily go in the gun and the bolt closes (fairly) easily; and the case stretches the minimum amount.

To reduce the amount of resizing needed to FL size cases, we can re-set the sizing die, up. This increases the case headspace dimension, making it closer to the gun headspace dimension. Using the 1.630"-1.640" example above, if we raise the die .005", then the case headspace becomes 1.635", the gun headspace stays at 1.640" and the difference falls from .010" to .005"
Repeatably setting this "die raise" can be done with these shims.



Repeatably reducing cartridge headspace can also be done by increasing the shell holder thickness, using these shell holders.

COMPETITION SHELLHOLDER SETS
Makes every die a custom die!

Now you can control headspace. The new Redding Competition Shellholders are packaged in five piece sets in .002” increments (+.002”, +.004”. +.006”, +.008” and +.010”). Each shellholder has a distinct black oxide finish and is clearly marked to indicate the amount it will decrease case-to-chamber headspace. You can now easily adjust the shoulder bump to customize cases to your specific chamber.


NOW THE SAVAGE GUNS
The/a distinguishing characteristic of the Savage guns is that the barrel may be changed, and chamber headspace adjusted fairly easily by the amateur shooter.

308 WINCHESTER HEADSPACE SAAMI DRAWING
CHAMBER 1.630"-1.640"
CARTRIDGE 1.634"-.007"
OR
1.627"-1.634"

Any set of dies/shell holder will produce FL sized cases, with FL die set to a dead stop, of a certain length. While I don't know what that length is, and it can vary from die set to die set, correct in-spec dies, from 1.625" (GO GAUGE -.005") to 1.634" (SAAMI max).
The headspace in a Savage barrel/gun can be set in several ways.
If the gun headspace is set using GO and NO GO gauges, headspace will be at or slightly greater than 1.630".
Minimum headspace difference, cartridge to gun, can be set by adjusting the die as explained above.

Or

The gun headspace can be set using fired FL sized cases and a roll of Scotch tape, by adjusting/setting the barrel. Using this method, the die MUST be set the same ALWAYS for the cartridge headspace to remain the same and the head clearance to remain the same.
I set the die to the dead stop position.

[bigedp51]

joeb33050

The gun headspace can be set using fired FL sized cases and a roll of Scotch tape

Without a GO gauge you do not have a reference zero point for your cartridge headspace gauges because they are not calibrated.

Without a GO gauge you will not know how long your cartridge headspace is after you resize your case.

A simple Google search looking at Scotch tape type brands and their MSDS sheets will show you Scotch tape thickness can vary by as much as .005 in thickness therefore Scotch tape isn't calibrated for checking headspace.

On top of this you sent me a PM and stated you are writing a book on this subject and you are just fishing for material and answers for your book.


I know one thing, I don't buy books by an author that doesn't know anything and plagiarizes the work of others.

It time for 82boy to lock and delete this entire posting.

I told you I don't want my name in a coloring book or anything to do with it.

http://i122.photobucket.com/albums/o254/bigedp51/copycat.jpg

[joeb33050]

Sorry to bother you about the book, it won't happen again.
I headspace Savage barrels with fired FL sized cases, and then shoot them. 308 Win, 22-250 3 barrels, 243 so far. Several dozen barrel changes. 2 yesterday. The technique is clear and here.
And, I don't own a GO or NO GO gauge.
They're nice, but not mandatory.
I'm not recommending my method, but it do work.
Thanks for your help;
joe b.













joeb33050

The gun headspace can be set using fired FL sized cases and a roll of Scotch tape

Without a GO gauge you do not have a reference zero point for your cartridge headspace gauges because they are not calibrated.

Without a GO gauge you will not know how long your cartridge headspace is after you resize your case.

A simple Google search looking at Scotch tape type brands and their MSDS sheets will show you Scotch tape thickness can vary by as much as .005 in thickness therefore Scotch tape isn't calibrated for checking headspace.

On top of this you sent me a PM and stated you are writing a book on this subject and you are just fishing for material and answers for your book.


I know one thing, I don't buy books by an author that doesn't know anything and plagiarizes the work of others.

It time for 82boy to lock and delete this entire posting.

I told you I don't want my name in a coloring book or anything to do with it.

http://i122.photobucket.com/albums/o254/bigedp51/copycat.jpg

[bigedp51]

joeb33050

I don't own a GO or NO GO gauge.
They're nice, but not mandatory.

http://i122.photobucket.com/albums/o254/bigedp51/pp3.jpg