Headspacing - Page 2

F. Guffey · July 10, 2010, 09:19 AM

Head space: I have never seen a thread on a forum end with "OH!, I see" or "Now I understand" This could be caused by the confusion when the story starts with "Head space is determined by the datum line" Think about it, what is the person going to do with a line described by someone that does not know how to use the information and when pressed runs out of gas real fast.

The DATUM is not a line, it is a circle/round hole. the 338/06 datum is .400, the 30/06 is .375 (3/4 inch), I make up datums, the .400 circle round hole datum works for 30/06, 270 25/06 7.7 Japanese and many other chambers and cartridge, both the case and chamber have datums. I was at the Dallas Market Hall gun show when I found a box of what looked like junk to most, I said DATUMS!!!, I got responses starting with "WHERE", I DON"T SEE ONE" then "WHAT DOES A DATUM LOOK LIKE"?

I determine head space first, then size, load and fire, that is form first then fire, Most fire first to determine the effect the chamber has on the case, again there are not of tools required that is not already owned by the reloader, the difficulty with tools is teaching someone how to use them. If the reloader/smith understood datum, round hole, circle checking the effect the chamber had on the case when fired would be something they could do setting at the bench at the firing range, something like doing it instead of talking about it.

Once DATUM is understood forming reloaders would under stand moving the shoulder forward can be replaced by moving the shoulder back, that eliminate "fire forming'. again I form first then fire, I do not form cases then fire form, this saves a trip to the range, there are times when fire forming is necessary or expensive as with cases that cost $1.75 each.

http://www.z-hat.com/Cylinder.htm

even with a case that is 2.650 long and without a shoulder the reloader must notice the threads on the press allows the die to be adjusted to the shell holder, if a case is formed by moving the shoulder back and after sizing the case presents head space in the chamber the reloader does not understand DATUMS, because after sizing the case can be measured for length from the DATUM (round hole circle) shoulder! back to the head of the case, 'back to the start' I determine head space first then form, after forming and or sizing and if I am able to transfer one measurement from the chamber to the press, sized case fit.

One thought at a time, again Hatcher thought the 30/06 ammo used in the early 1903s was blowing the rifle up, first was head space, then case head protrusion etc., he moved the shoulder forward .125, 1/8 of an inch and expected incipient case head separation, catastrophic failure etc., what did he get when the cases were ejected, Hatcher Modified 06 +.125 wildcat cases. something like firing an 8mm57 in a 8/06 chamber, when cases are ejected they take on the appearance of 8/06 cases with short necks. ( and spare me) the 'firing pin strikes the primer, the case, bullet and powder accelerate to a speed that allows the primer to out run the firing pin' the primer is crushed before the total weight of the ammo can think about getting out of the way.

And my 1917 Eddystone with .016 thousands head space, I could fire new ammo to form cases, I choose to form cases that are .014 longer from the head of the case to the shoulder than full length sized cases (factory ammo), the shoulder of the 280 Remington case is ahead of the 30/06 by .041 thousands, by sizing the 280 to 30/06 I add .014 to the length of the case by knowing when to quit, and the shoulder is not pushed back when forming, it is arsed, part of the shoulder becomes part of the neck and part of the case body becomes p[art of the shoulder. and bumping sounds like an accident, to avoid accidents know where you want the shoulder.

Learn to transfer a measurment with a transfer.

F. Guffey

F. Guffey · July 10, 2010, 09:23 AM

forgive, should have ben ' earased'.

F. Guffey

wncchester · July 10, 2010, 10:00 AM

"I have never seen a thread on a forum end with "OH!, I see" or "Now I understand" This could be caused by the confusion when the story starts with "Head space is determined by the datum line" Think about it, what is the person going to do with a line described by someone that does not know how to use the information and when pressed runs out of gas real fast." (emphesis added)

Ah, Guffey, you sure get it don't you!

Why anyone thinks tossing in esotoric things like a box of datums or fumbling around with how rimmed and belted and military chambers are in some magical way "different" from other bottle neck cartridges is helpful escapes me.

dmazur · July 10, 2010, 10:16 AM

Oops. I said (earlier) -

Quote:

I believe this is related to how well your extractor holds the case, but it is possible for the firing pin to drive the case forward until the shoulder touches and not fire the primer.

I meant to say, it is possible for the case to move forward, not be driven forward. Then the firing pin simply can't reach it. You are correct...the inertia of the case keeps it from being "driven" forward. But, if the extractor doesn't hold it back against the bolt face, gravity can make it move forward...

mehavey · July 10, 2010, 11:24 AM

Quote:

Hatcher thought the 30/06 ammo used in the early 1903s was blowing the rifle up, first was head space, then case head protrusion etc., he moved the shoulder forward .125, 1/8 of an inch and expected incipient case head separation, catastrophic failure etc., what did he get when the cases were ejected, Hatcher Modified 06 +.125 wildcat cases.

I couldn't let this one go, so I moved my right hand 15 inches to the right and picked up my Hatcher's Notebook where it has been in-and-out of my bookcase for the last 30 years.

Hatcher's "Headspace" chapter is interesting because it's self-contradicting. In the first part (pp 232- 243) he discusses headspace definition and how excessive headspace can do bad things to you. He concludes this section with a graphic picture of that bad juju we've been discussing:

Then he says two interesting things.

Quote:

"It just so happens I have un unusual amount of personal experience with this matter of excess headspace and separated cases... I had charge of the Army Machine Gun Schools.... In those (1916-17) days Frankfort Arsenal made the 30-06 cartridge case of very hard brass to make extraction easier.... would separate in a hurry if the headspace got the least bit over the limit.... I never saw enough gas escape to hurt anyone [in a machine gun]. However bear in mind we were using the old 30-06 cartridge with...not over 50,000 pounds pressure. With some of the super high intensity loads...today, any headspace over normal can be dangerous.

In 1917, Frankfort arsenal began making cases much softer to get away from these separations...."

Hatcher then spends the next 10 pages telling the gentle reader that headspace doesn't much matter, ...that the case would be held by the extractor from going forward much and instead blow the shoulder forward as F.Guffey suggests. But Hatcher then carefully notes that if the excess headspace is caused not by reaming the front of the chamber, but worn bolt lugs at the back of the chamber, the case does move forward, the shoulder locks into the chamber as pressure builds, and the rear/head portion stretches back to meet the bolt face "...where ruptures would be more likely." [The gentle reader should note that excess headspace never grows at the chamber's front. It grows from bolt/lug setback.]

Hatcher then notes the (in)famous Lt (USNR) Wyckoff experiment wherein a test barrel/action using no extractor to hold the case was successively reamed forward until headspace clearance was ten times normal (0.065" vs normal 0.006"). Inertia alone from the big 30-06 cartridge was apparently enough to set off the primer and the case allowed to move/not move/go where it wanted after that. Hatcher says "It is quite interesting to note that even with the fantastically excessive headspace used in this test gun, there were no ruptu[res]... and the fired cases showed only slight signs of case stretching." Even more interesting, however, is reading between the lines of Wcykoff's conclusion of increased throat erosion as the gasses passed the bullet body, supported by the observation that the velocity increased as the bullet had more freebore to move before encountering the lands. This tells me that the heavy case tended to hang back at the bolt face... hence less-than-expected stretch for this particular experiment.

BOTTOM LINE: Excessive headspace isn't such bad juju after all. Right?

WRONG.

Go back to the beginning, where Hatcher was personally getting head separations "...in a hurry if the headspace got the least bit over the limit." What was the reason? "...very hard brittle brass..." from the Frankfort arsenal -- a condition the arsenal then deliberately changed to make the case softer, and more amenable to stretch rather than rupture at first shock.

Now gentle reader, what is a reloader doing when he repeatedly fires a case which stretches at its web base at each firing. Can the gentle reader spell "...work-hardened embrittlement"? Go back and read the paragraph above this one again.

Headspace matters for a reloader... Big Time.
He'd better understand it.

Now, Shredder4286, aren't you glad you started this thread?

shredder4286 · July 10, 2010, 12:15 PM

despite all the arguments, i understand what i wanted to know in the first place, an that's all that matters

thanks to all those who gave info

F. Guffey · July 10, 2010, 06:12 PM

What I meant to say is I am not a fan of Hatcher, there was under no circumstance Springfield and or Rock Island issue a rifle without the head space stamped on the rifle as a part of the permanent record, not by design but by default the 03 was/is one of the few rifles that can be checked for head space with the companion to the press tool, the feeler gage

When the bolt closed the chamber got dark and the lights went off for Springfield and Hatcher. Checking head space on the 1903 was easy because of the small gap between the third lug and rear receiver ring, the 1903A3 became difficult because the gap increased, meaning a thicker feeler gage was/is required. Head space on the 1903 and 1903A3 can be checked for head space with the ammo that is fired in it, as opposed to using go-gage that that will always chamber (unless the chamber is short chambered, another day).

Hatcher's wildcat modified chamber has the same difference in length from the head of the case to it's shoulder as the 8/06 and 8mm57, Hitcher's wildcat had an increase of .125 the 8/06 has an increase of .129 over the 8mm57, with new or once fired cases and fired by accident the 8mm57 are formed to 8/06 with short necks, and the 308 Winchester for the same reason, mistake or excited, have been fired in a 30/06 chamber, cases when ejected have the appearance of a straight wall case with little shoulder and no neck.

Back to head space, Hitcher's creation did not head space, the 8mm57 does not head space on in the 8/06 chamber and there is a chance the 308 W can jam in the chamber because the body of the case is larger in diameter by .011 than the 30/06 at the same point when measured from the head of the case, then there are those that claim they can chamber a 308 W in their 30/06 without effort, I say they should check their chamber for expansion, something like firing a case with recovery (spring back) the chamber expanded and did not recover (spring back).

Telling someone it can not be done is not what I do.

The length of the case from the head of the case to the shoulder off sets head space if the reloader can keep up with it, it could require some to STEP AWAY from the computer.

F. Guffey

F. Guffey

July 10, 2010, 09:19 AM	#26
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	Head space: I have never seen a thread on a forum end with "OH!, I see" or "Now I understand" This could be caused by the confusion when the story starts with "Head space is determined by the datum line" Think about it, what is the person going to do with a line described by someone that does not know how to use the information and when pressed runs out of gas real fast. The DATUM is not a line, it is a circle/round hole. the 338/06 datum is .400, the 30/06 is .375 (3/4 inch), I make up datums, the .400 circle round hole datum works for 30/06, 270 25/06 7.7 Japanese and many other chambers and cartridge, both the case and chamber have datums. I was at the Dallas Market Hall gun show when I found a box of what looked like junk to most, I said DATUMS!!!, I got responses starting with "WHERE", I DON"T SEE ONE" then "WHAT DOES A DATUM LOOK LIKE"? I determine head space first, then size, load and fire, that is form first then fire, Most fire first to determine the effect the chamber has on the case, again there are not of tools required that is not already owned by the reloader, the difficulty with tools is teaching someone how to use them. If the reloader/smith understood datum, round hole, circle checking the effect the chamber had on the case when fired would be something they could do setting at the bench at the firing range, something like doing it instead of talking about it. Once DATUM is understood forming reloaders would under stand moving the shoulder forward can be replaced by moving the shoulder back, that eliminate "fire forming'. again I form first then fire, I do not form cases then fire form, this saves a trip to the range, there are times when fire forming is necessary or expensive as with cases that cost $1.75 each. http://www.z-hat.com/Cylinder.htm even with a case that is 2.650 long and without a shoulder the reloader must notice the threads on the press allows the die to be adjusted to the shell holder, if a case is formed by moving the shoulder back and after sizing the case presents head space in the chamber the reloader does not understand DATUMS, because after sizing the case can be measured for length from the DATUM (round hole circle) shoulder! back to the head of the case, 'back to the start' I determine head space first then form, after forming and or sizing and if I am able to transfer one measurement from the chamber to the press, sized case fit. One thought at a time, again Hatcher thought the 30/06 ammo used in the early 1903s was blowing the rifle up, first was head space, then case head protrusion etc., he moved the shoulder forward .125, 1/8 of an inch and expected incipient case head separation, catastrophic failure etc., what did he get when the cases were ejected, Hatcher Modified 06 +.125 wildcat cases. something like firing an 8mm57 in a 8/06 chamber, when cases are ejected they take on the appearance of 8/06 cases with short necks. ( and spare me) the 'firing pin strikes the primer, the case, bullet and powder accelerate to a speed that allows the primer to out run the firing pin' the primer is crushed before the total weight of the ammo can think about getting out of the way. And my 1917 Eddystone with .016 thousands head space, I could fire new ammo to form cases, I choose to form cases that are .014 longer from the head of the case to the shoulder than full length sized cases (factory ammo), the shoulder of the 280 Remington case is ahead of the 30/06 by .041 thousands, by sizing the 280 to 30/06 I add .014 to the length of the case by knowing when to quit, and the shoulder is not pushed back when forming, it is arsed, part of the shoulder becomes part of the neck and part of the case body becomes p[art of the shoulder. and bumping sounds like an accident, to avoid accidents know where you want the shoulder. Learn to transfer a measurment with a transfer. F. Guffey

July 10, 2010, 09:23 AM	#27
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	forgive, should have ben ' earased'. F. Guffey

July 10, 2010, 10:00 AM	#28
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	"I have never seen a thread on a forum end with "OH!, I see" or "Now I understand" This could be caused by the confusion when the story starts with "Head space is determined by the datum line" Think about it, what is the person going to do with a line described by someone that does not know how to use the information and when pressed runs out of gas real fast." (emphesis added) Ah, Guffey, you sure get it don't you! Why anyone thinks tossing in esotoric things like a box of datums or fumbling around with how rimmed and belted and military chambers are in some magical way "different" from other bottle neck cartridges is helpful escapes me.

July 10, 2010, 12:15 PM	#31
shredder4286 Senior Member Join Date: May 13, 2010 Location: NE Washington Posts: 361	despite all the arguments, i understand what i wanted to know in the first place, an that's all that matters thanks to all those who gave info

July 10, 2010, 06:12 PM	#32
F. Guffey Senior Member Join Date: July 18, 2008 Posts: 7,249	What I meant to say is I am not a fan of Hatcher, there was under no circumstance Springfield and or Rock Island issue a rifle without the head space stamped on the rifle as a part of the permanent record, not by design but by default the 03 was/is one of the few rifles that can be checked for head space with the companion to the press tool, the feeler gage When the bolt closed the chamber got dark and the lights went off for Springfield and Hatcher. Checking head space on the 1903 was easy because of the small gap between the third lug and rear receiver ring, the 1903A3 became difficult because the gap increased, meaning a thicker feeler gage was/is required. Head space on the 1903 and 1903A3 can be checked for head space with the ammo that is fired in it, as opposed to using go-gage that that will always chamber (unless the chamber is short chambered, another day). Hatcher's wildcat modified chamber has the same difference in length from the head of the case to it's shoulder as the 8/06 and 8mm57, Hitcher's wildcat had an increase of .125 the 8/06 has an increase of .129 over the 8mm57, with new or once fired cases and fired by accident the 8mm57 are formed to 8/06 with short necks, and the 308 Winchester for the same reason, mistake or excited, have been fired in a 30/06 chamber, cases when ejected have the appearance of a straight wall case with little shoulder and no neck. Back to head space, Hitcher's creation did not head space, the 8mm57 does not head space on in the 8/06 chamber and there is a chance the 308 W can jam in the chamber because the body of the case is larger in diameter by .011 than the 30/06 at the same point when measured from the head of the case, then there are those that claim they can chamber a 308 W in their 30/06 without effort, I say they should check their chamber for expansion, something like firing a case with recovery (spring back) the chamber expanded and did not recover (spring back). Telling someone it can not be done is not what I do. The length of the case from the head of the case to the shoulder off sets head space if the reloader can keep up with it, it could require some to STEP AWAY from the computer. F. Guffey F. Guffey