Why "extractor headspacing" Doesn't Often Occur in the 1911

[35remington]

Included is a photo of a round placed under the extractor to show the gap between breechface and the case head when the round is bearing on the front of the extractor hook. This gap will increase slightly when the case is struck by the firing pin, as the case will "slide" down the front of the extractor hook and cant a little under the firing pin blow if it is so short that the extractor/breechface gap is less than the distance to the chamber shoulder.

In actual usage, the gap between breechface and case head when "headspacing" on the extractor is larger than that found in a combination of a long chamber and a short case in terms of headspacing. Both case and chamber would have to be considerably out of spec for the round to headspace on the extractor.

The normal situation, in 1911's, is that the round headspaces on the case mouth or the bullet.

Headspacing on the extractor is not the normal or common situation, despite the claims of some theorists.

In the photo, notice that the gap twixt case head and breechface is quite considerable when the round is "headspacing" on the extractor. Too great to make headspacing on the extractor the normal or standard situation.

http://i6.photobucket.com/albums/y228/johnnyrem/DSC02342.jpg

[C.F.Plinker]

This is a super picture and shows just what you are saying. I tried this using my 1911 except that I used the barrel to maintain alignment for the case. I got .048 worth of shims between the case and the bolt face when the barrel was at the case mouth. Then I moved the barrel into battery I only got a .017 space between the case and the bolt face. This confirms your conclusions above.

[Mk42gunner]

I personally think that in a 1911 of any caliber the round just lays in the chamber, and the inertia firing pin flies foward until it hits the primer. When we still had 1911-A1's in the Navy; it was a rare gun that the firingpim wouldn't protrude 3/8", if no case was there to stop it.

Robert

[35remington]

"how long is the chamber in YOUR GUN.
how long is the brass in your ammo
what is the distance to the crimp on you ammo"

Already covered that. In most instances it's a non issue. The chamber shoulder's headspacing.

I don't recall claiming this occurs on all automatics as I don't own all brands and I don't recall speculating this occurs on all brands. Just some of them I know about for sure.

I do know about the 1911.

Kinda makes the point pretty well, wouldn't you agree?

Now, I admittedly don't know exactly how much case head/breech clearance there is when the rim's hanging on the extractor in each and every brand of gun out there, but why do you suppose they put chamber shoulders in the barrels of the rest of these automatics as well? I can't think of a single manufacturer that does not.

So that brings me to my point.

You might want to rethink the "most of the time it headspaces on the extractor" bit. Since the case rim approaches the extractor at an angle from below, and that this angle has to vary depending upon the feed length of the round, the room for the rim has to be noticeably larger than the rim itself. Thus creating some extra needed space.

This space allows the chamber shoulder to work to headspace in most instances, is what I'm saying, in the guns I've examined.

I'd start measuring your 1911's, as that was the original topic, and see for yourself.

[bohokii]

when i load a new bullet i take my tightest barrel and check to make sure when seated and crimped it sits flush with the hood

[beagle]

Fellers, this has been kicked around for years and no one knows. I tend to go with the extractor train of thought.

The headspacing on the mouth theory is good and may happen but I've loaded too much .45 over the last 50 years to beleive that it's the only thing happening.

Measure say 50 assorted .45 ACP case lengths and you'll get readings all over the place. Now, load those same 50 cases and you'll get reliable firing and functioning in a M1911.

This tells me that the case may or may not be headspacing on the case mouth due to the various case lengths many of which are undersize to the point where you would encounter headspace probles in a rifle.

I'm thinking and this is is from a funtional standpoint that the M1911 if it encounters the correct length case will headspace on the case mouth and all is well. If the case is shorter, the overly generous extractor will hold it back against the breech and the positive firing pin system on the M1911 system will set it off. Any headspace problems will be taken up and compensated for in the functioning cycle.

Having fired an old M1A1 THompson and several iterations of the M3 Grease Gun quite extensively, they have a fixed pring pin and the same set of sloppy tolerance to work with and both seem to take all things considered in stride.

Just my opinion. It works really well in either case./beagle

[35remington]

Beagle, I never said case mouth headspacing was the only thing happening. I said it happens far, far more often than headspacing on the extractor, given typical tolerances in chambers and cases.

Mike, no, the title always said 1911. You know that as you responded to it after it was posted and before it was edited. I had the phrase "extractor to breechface" when I should have said "case head to breechface" so I changed it to more correctly identify the distance to the players in the headspacing equation.

As regards headspacing, let's look at the numbers. The case head is around 0.048" from the breechface in the picture.

Now, let's take an absolutely maximum chamber (most chambers are shorter than this....measure your own and see) and a short case......let's say it's twenty thou shorter than the .898" maximum (and most of my cases are longer than this as well, more often in the .883-.888" range after measuring quite a few). This case dimension is after sizing as I find a fired case grows from three to five thousandths after sizing. It's only the sized case that gets headspaced and fired in the gun.

That's 0.920" on the very generous chamber, and .878" on the quite short case. Forty two thousandths.....still shorter than the extractor/breechface gap, and I'm taking a worst case for chamber and a pretty short one for the case length. It is still less than the extractor/breechface gap. And then the case is headspacing on the mouth, if it isn't on the bullet.

The numbers aren't on the side of extractor headspacing as the default condition for the 1911.

I invite you to do some measuring of your own guns and cases. I don't expect you to take my word for it. Please check and see for yourself. When cutting chamber depth, you can figure than the dimensions for most guns ain't gonna be the maximum or the minimum most of the time...it's more likely in the middle.

Can extractor headspacing occur? Sure.

Does it happen sometimes? Sure, with a short case and a long chamber.

But to argue extractor headspacing is the norm in the 1911 is in my opinion erroneous. The chamber shoulder's there for a reason. And normal tolerances prevent extractor headspacing most of the time. FWIW, Charles Petty held forth on this theme for quite awhile (years and many magazine articles) until realities were pointed out to him, and he recanted in Handloader magazine. If a die hard like Petty can see it's the norm to not headspace on the extractor most of the time, perhaps you can too?

On edit:
Mike, are you happy with the numbers now? I gave you some generous numbers to get the benefit of the doubt on your side. In fact, I went out of the way to get an atypical situation that's really not representative of most guns and most cases, as my chambers aren't the maximum and my cases are longer than that, as likely yours are. BTW, when I said I covered it before, it was in the other thread, so the numbers were indeed mentioned before. I needed to start a new thread to avoid totally hijacking it.

[StarMetal]

Fellers, this has been kicked around for years and no one knows. I tend to go with the extractor train of thought.

The headspacing on the mouth theory is good and may happen but I've loaded too much .45 over the last 50 years to beleive that it's the only thing happening.

Measure say 50 assorted .45 ACP case lengths and you'll get readings all over the place. Now, load those same 50 cases and you'll get reliable firing and functioning in a M1911.

This tells me that the case may or may not be headspacing on the case mouth due to the various case lengths many of which are undersize to the point where you would encounter headspace probles in a rifle.

I'm thinking and this is is from a funtional standpoint that the M1911 if it encounters the correct length case will headspace on the case mouth and all is well. If the case is shorter, the overly generous extractor will hold it back against the breech and the positive firing pin system on the M1911 system will set it off. Any headspace problems will be taken up and compensated for in the functioning cycle.

Having fired an old M1A1 THompson and several iterations of the M3 Grease Gun quite extensively, they have a fixed pring pin and the same set of sloppy tolerance to work with and both seem to take all things considered in stride.

Just my opinion. It works really well in either case./beagle

John,

I haven't looked at the grease gun but the Thompson M1A1 has a spring loaded firing pin that a hammer (looks like a triangular piece of metal) hits it. The hammer is pinned and it's no the very front of the bolt and pinned such that a portion of it protruded in front of the bolt and when the bolt slams forward on the receiver wall the protruding part of the hammer hits first driving the firing pin. If they made some Tommy guns with fixed pins I'm not aware of it. What say you?

Joe

[Russel Nash]

What is the point of this thread?

Where is the original poster of this thread trying to go with this?

Is the OP also on the SASS wire forums?

I only ask that because over the weekend I dodged in there to see what might be new on the tin foil hat conspiracy theory scene.

And some guy asked about reloading for a 1911.

I told them all pretty what mike in co is saying.

The danged round headspaces off the extractor hook.

And I mentioned that the I had plenty of success shooting 9mm Parabellum/Luger (which is technically 9X 19) out of a Colt that was chambered in 9X23.

Those four extra milimeters got to go somewhere.

Right?

How did those Para/Luger rounds fire if it wasn't for the extractor hook holding it tight to the breechface.

anywhooo... you woulda thunk that I was tellin' all the SASS'ers the world wasn't actually flat.

This sounds like one of those :takinWiz: kinda threads to me.

[Russel Nash]

One way to test this is to take .45 G.A.P brass and shoot it in the gun as is.

I am gonna bet right now that they will all go bang.


Okay... now take the extractor out of that same gun.

Again, load it up with .45 G.A.P. brass and try to fire it off after the slide has slammed into battery.

What happens then, eh?

[35remington]

"The danged round headspaces off the extractor hook."

Not most of the time. Not in the 1911. The 1911 was the topic of this thread.

Since I'm the OP, I'm simply pointing out the realities of headspace in the 1911.

Actually, the numbers pertaining to extractor distance from the breechface, typical case length and chamber dimensions say the 1911 doesn't headspace on the extractor most of the time. It's not just me.

Do some measuring for yourself of your own gun and cases and figure it out by so doing. That's all I ask.

Simple, no?

Guys, once again, for emphasis.....I didn't say the gun can't headspace on the extractor. I'm saying most of the time it does not, contrary to some opinions.

I don't think I can make that any clearer, as I've repeated myself several times.

[Russel Nash]

so all you're saying is sometimes it does headspace off the extractor hook

And at other times it does NOT heaspace off the extractor hook

[smilie=1:

Are you sure you ain't running for office?

So what happens if I take some of my .45 ACP brass and trim... oh... I dunno... an eighth off it.

Then I put a primer in it.

And just a primer.

Then I stick it in my gun, the complete gun with the extractor in place and everything...and squeeze the trigger and it goes BANG!

And then I take the extractor out, and take another piece of trimmed down brass that has been just primed ....squeeze the trigger... and it doesn't go bang.

What do I get...do I get a prize?

I mean do I get more than two pieces of brass that I will have to throw into the trash can?

Sounds to me like somebody's been reading the Kuhnhausen manuals.

[StarMetal]

so all you're saying is sometimes it does headspace off the extractor hook

And at other times it does NOT heaspace off the extractor hook

[smilie=1:

Are you sure you ain't running for office?

So what happens if I take some of my .45 ACP brass and trim... oh... I dunno... an eighth off it.

Then I put a primer in it.

And just a primer.

Then I stick it in my gun, the complete gun with the extractor in place and everything...and squeeze the trigger and it goes BANG!

And then I take the extractor out, and take another piece of trimmed down brass that has been just primed ....squeeze the trigger... and it doesn't go bang.

What do I get...do I get a prize?

I mean do I get more than two pieces of brass that I will have to throw into the trash can?

Sounds to me like somebody's been reading the Kuhnhausen manuals.

Take a look at the 45 acp case specs here:
http://stevespages.com/jpg/cd45acp.jpg

Now if you cut that 1/8th inch off it may not necessarily go a lot deep in the chamber if everything is correct. It's not a straight walled cartridge. What to do it cut 3/8th inch off and see how far it will chamber with the barrel out of the gun. No far using carbide sizer, use the correct regular lube steel sizer die as it sizes them tapered.

Just for comparison heres the 45 Gap case specs:
http://stevespages.com/jpg/cd45gap.jpg

Is a light beginning to go on?

Joe

[Russel Nash]

Was the "is the light beginning to go on?" comment directed at me?

[Char-Gar]

Being a fan of the 1911 pistol, here is my $0.02.

In a properly set us mil-spec 1911/1911A1 or Colt Govt. Model the round will headspace on the case mouth as designed in spite of minor variations in case length. This is due to the extra room between the breech face and the back of the extractor hook.

If you have a long chamber or a short case, will the round still fire, being held in place by the extractor to receive the firing pin blow? Heck yes.

On all of these fancy smancy custom and semi-custom 1911a who knows how they are set up. I don't as I don't have any interest in them. I like a well fitted basic 1911A1, with good sights and a decent trigger. You can keep the rest.

I really didn't know there was any kind of argument about this.

[35remington]

"so all you're saying is sometimes it does headspace off the extractor hook

And at other times it does NOT heaspace off the extractor hook"

And then some comment about my running for office? Now, Russell, that's simply being argumentative without bringing anything to the topic yourself.

What relevance does your deliberately overtrimmed super short case (which has no similarity to a 45 ACP case as reloaded by most of us) have to this discussion about the typical condition? I simply said this:

"Guys, once again, for emphasis.....I didn't say the gun can't headspace on the extractor. I'm saying most of the time it does not, contrary to some opinions.

I don't think I can make that any clearer, as I've repeated myself several times."


There's such a thing as willful ignorance. If you don't want to measure these things yourself, then we have a discussion where one side wants to tilt at windmills and dream up irrelevant scenarios and doesn't care to discover things for themselves.

I'm suggesting you can clear this up for yourself by doing a little measuring. That's all it takes. Why such resistance to enlightenment I can't quite understand.

What price knowing, rather than guessing?

For myself, I'd much rather know.

So I presume no one wants to do any measuring of their own 1911, of their own chambers and cases? That's somewhat disappointing, but perhaps not surprising if someone's afraid a pet theory may get refuted.

[Russel Nash]

^^^Agree'ed... I don't know where the argument was either...especially when the OP uses language (I am paraphrasing here).

"Sometimes the round's mouth headspaces off the chamber "shoulder". At other times it can headspace off the extractor's hoo, and that's ohh-kaayy."

Can we please get back to more important stuff, please?

Where the .45 ACP round headspaces can wait til late January or February when we are all snowed in?

Let's focus more on the whole 9mm vs. .38Special debate.

I think we are really making progress with that one.

:coffee:

[35remington]

Russell, still tilting, I see. My position has been clearly stated here more than once and you are gleefully determined to misrepresent it. I think I'll ignore your comments from here on out as you're not adding anything substantive to the discussion.

Measuring these things would be more productive and enlightening for you, but you've got to make your own decisions, I'm sure.

Chargar, this has been going around for awhile in various places, printed text to the internet. Some facts about tolerances don't get through to those who don't want to listen.

All I offer is an opportunity for those interested to resolve the issue for themselves if they're observant and care to do so.

If they're not interested, I don't particularly care, but I'd like to think knowing would have some value to them.

[Russel Nash]

@ 35Remington... I didn't have to measure anything.

I did just take an empty or fired case and stuck into the breechface, and the extractor hook held it there just fine. In all sorts of positions too. Right side up, upside down, pointing at the sky, pointing at the floor. Why, dad-gum-it... that case sure was held in there pretty good by that extractor.

Then I took a small-ish flat bladed screwdriver and pried between the headstamp of the case and the breechface. Yeah, until it looked exactly like the pic in your OP.

And my point to all this is... I guess your pic is kinda a red herring.... three card monty kinda thing...while everybody is looking at that glaring 1/16th of an inch gap (or thereabouts) between the breechface and the head stamp, what nobody is noticing at least not yet...is that it is the spring-i-ness of the extractor that is pushing it against the port side of the breechface.

I took the extractor out of my slide, and while I had the slide upside down in my left hand, I pushed the same case into the breechface. Then I flipped the slide right side up. And darn it... that case came falling out.

All that "divot" in the extractor is doing is providing enough tension against the case in the breechface "pocket" to give the firing pin enough resistance and time to crush the primer in a split second.

I guess really to make this a fair test since both the 9mm and the .45 ACP are tapered rounds.... we need to find a Colt 10mm delta elite and feed it .40 S and W rounds.

Methinks it'll run just fine too.

[StarMetal]

Russell, You're a character and no the light wasn't directed totally at you.

Joe

[mike in co]

ok...lets get my 2 cents worth correct.

i AGREE that some or most 1911 seldom fire from the extractor. the 1911 is ONE platform. to make ASSUMPTIONS based on one platform is poor logic.

i DISSAGREE that firing from the extractor seldom happens in other guns.

i BELIEVE that most semi's will fire from the extractor.

i have the PROOF in my shop.

since this america, each is allowed thier own opinion

mike in co

[beagle]

Joe...as well as I recall, the M1A1 has the fixed firing pin. They were the cheapies but mine always shot...on full auto only. The semi function was messed up. The remainder....the 21s, 27s and 28s had the removable firing pins and were more expensive to manufacture. Man, you priced Thompsons lately? I had sticker shock when I last looked./beagle


John,

I haven't looked at the grease gun but the Thompson M1A1 has a spring loaded firing pin that a hammer (looks like a triangular piece of metal) hits it. The hammer is pinned and it's no the very front of the bolt and pinned such that a portion of it protruded in front of the bolt and when the bolt slams forward on the receiver wall the protruding part of the hammer hits first driving the firing pin. If they made some Tommy guns with fixed pins I'm not aware of it. What say you?

Joe

[beagle]

Fellers, I agree. No use to get upset about this. We're just talking here. I'll grant that the M1911 is set up to headspace on the case mouth.

But due to tolerances in ammo, barrels, slides, extractors and firing pins, sometimes they're forced to headspace on the extractor and they work and work darn well.

Having fiddled with M1911s and M1911A1s now for 50 years and over 20 of that in the Army, I've seen some loose M1911s and encountered some crappy milspec ammo.

But, old slabsides will always shoot and that's what counts. Now, I'm not sure what the newer guns are set up at and they may well headspace like we want them to on the case mouth but I'll bet that the slack due to dimensions being off is taken up by the extractor./beagle

[StarMetal]

Joe...as well as I recall, the M1A1 has the fixed firing pin. They were the cheapies but mine always shot...on full auto only. The semi function was messed up. The remainder....the 21s, 27s and 28s had the removable firing pins and were more expensive to manufacture. Man, you priced Thompsons lately? I had sticker shock when I last looked./beagle

John,

You're right. The M1 model had the floating firing pin. Then the M1A1 went to a fixed pin like you mentioned. The earlier models also had the floating pins.

Joe

[Russel Nash]

I'll be the first to apologize. Sorry folks!

I was feeling catankerous tonight.

I have been cooped up inside all day.

On the way out this morning, I had a tree branch on my hood when I was about to hop into my truck.

As I was about to put the key in the truck's door when I hear this CRRRRAAAACCKKKK noise coming from up above me.

I put my arms over my head and ran like a little girl out into the neighbor's yard.

CRASH!

A big ol' limb came falling down and almost took me out and half the deck. Luckily that one missed the truck.

However the one that was still on my hood gave it quite the dent.

so with the weather the rest of the day, I have been all cooped up.

I guess the cabin fever is setting in. :killingpc

[softpoint]

ok...lets get my 2 cents worth correct.

i AGREE that some or most 1911 seldom fire from the extractor. the 1911 is ONE platform. to make ASSUMPTIONS based on one platform is poor logic.

i DISSAGREE that firing from the extractor seldom happens in other guns.

i BELIEVE that most semi's will fire from the extractor.

i have the PROOF in my shop.

since this america, each is allowed thier own opinion

mike in co

FWIW, I have a Glock M20, 10mm. I was going to get a .40 S&W barrel for it, One of my buddies says, "What for?" And he proceeded to tell me to just shoot .40 out of the gun as is. So Itried it and it works perfectly, anyway in my gun, so those cartridges are being held against the breechface by the extractor. All the old sources I have DO, however claim that straightsided rimless pistol cartridges headspace off the mouth. I'd probably say that they are SUPPOSED to headspace off the mouth, but in the case of that dimension being excessive, many will fire off the extractor....?:-|

[danski26]

I did some measuring on my Springfield;

Depth from chamber end "step" to barrel hood .749"
Gap from barrel hood to breach face on slide .202"

Total .951"

I measured 10 pieces of once fired, sized, mixed headstamp brass AVG .886" (high .891" / low .873")

Gap between the cartrige head and the breach face when place under the extractor .021"
(case was cut back to .839" to be sure not to contact step in chamber, also cartidge case was not being stopped from going into the chamber by any case taper as it fell far into the chamber when tried off off the extractor.)

On my 1911 for the case to contact the step in the chamber it would have to be at least .951" long.

Furthermore, the gap when held only by the extractor is very small at .021"

I do remember the article Charlie did in handloader on this issue. I will have to find it to see what his testing methods were and any conclusions. If anyone knows the issue# it would save me some time.

[1874Sharps]

Gentlemen,

First of all let me say that we are indeed friends here, and that though we may hold different views and opinions on this issue and others as well, that does not overshadow or minimize that basic fact. I have enjoyed the stimulating discussion and evidence and views put forward by all of you.

In the case of the 1911 45 ACP I wonder if there is more wiggle room in the headspace spec due to the relavitely low pressure at which it operates. Headspace is important because if it is excessive, the case acts as a jackhammer after it fires and hammers the bolt or slide, etc. instead of pushing against it. I believe it was P. O. Ackley (I hope I am remembering the experimenter correctly) many decades ago who did a strength study of various rifle actions, increasing headspace systematically until he got a failure. In some cases he had to make extra long firing pins to do so. Eventually excessive headspace caused destruction of the action. Now consider the substantially lower pressure of the 45 ACP. Would this not lend itself to a higher margin of safety with a wider slop in the headspace spec? If that theory is correct, that would mean that the headspace spec would necessarily have to be tighter for pistols that shoot higher pressure rounds, such as a 1911 in 38 Super. I would be interested in hearing your opinions on this, as I value them. May God grant that I always be teachable and humble to admit when I am wrong.

[StarMetal]

Gentlemen,

First of all let me say that we are indeed friends here, and that though we may hold different views and opinions on this issue and others as well, that does not overshadow or minimize that basic fact. I have enjoyed the stimulating discussion and evidence and views put forward by all of you.

In the case of the 1911 45 ACP I wonder if there is more wiggle room in the headspace spec due to the relavitely low pressure at which it operates. Headspace is important because if it is excessive, the case acts as a jackhammer after it fires and hammers the bolt or slide, etc. instead of pushing against it. I believe it was P. O. Ackley (I hope I am remembering the experimenter correctly) many decades ago who did a strength study of various rifle actions, increasing headspace systematically until he got a failure. In some cases he had to make extra long firing pins to do so. Eventually excessive headspace caused destruction of the action. Now consider the substantially lower pressure of the 45 ACP. Would this not lend itself to a higher margin of safety with a wider slop in the headspace spec? If that theory is correct, that would mean that the headspace spec would necessarily have to be tighter for pistols that shoot higher pressure rounds, such as a 1911 in 38 Super. I would be interested in hearing your opinions on this, as I value them. May God grant that I always be teachable and humble to admit when I am wrong.


I think you are way off base on this. There is a major difference between head space and a sloppy chamber or fit. Head space is critical, not only for safety, but for insuring 100 percent firing of the cartridge, accuracy, etc.. When I load my 45's I don't seat the leading shoulder of the bullet flush or within the case. I load it out some and check the round by putting it in my barrel while out of the firearm. That's a good procedure rather then just load them like the book may say. Most book say leave about 1/32 of the shoulder exposed. My 1911's don't head space off the extractor, don't fire because the firing protrudes extra long, my cartridges are loaded so the case head is up against the breech face. You don't load your bottle neck cartridges with the shoulder sized back and increase the head space (even if it was a low pressure round) and hope that other ignition parameters come into play to fire the cartridge do you? I'll bet not.

The talk here is mainly why does the 1911 fire when the cartridge is much shorter then the chamber. That's not the ideal loading and the correct procedure had been repeated many times. We're just discussing WHY.

Joe

[scrapcan]

I would also like to see some case measurements after sizing is done with a carbide sizer die. Just how much case angle is introduced or removed with a short sizer ring of the carbide die? Ever seen the waist on a sized loaded case with a bullet in it. I see this with both 9mm and 45 acp using rcbs and lyman carbide dies. And then how much neck tension is generated by that case after sizing? If you are not sizing the brass correctly you can have issues with neck tension.

We also have to remember that there are two points of contact for the extractor. 1) the hook and 2) the tension on the side of the rim. You may not see the tension on the rim until the cartridge is in the chamber. if you have side tension on the rim it WILL hold the case to the side and to the rear, this also happens when you have fired brass with a rim that has been peened, push a well used case under the extractor and you will feel the side tension.

Also what happens when the case cutout in the breechface allows the case to be held against it when the link pushes the barrel up and pinning the brass to the rear/top of the breech face.

Another thing to remember is that the inertia of the loaded round going thru the loading cycle tends to keep the cartridge to the rear and may or may not allow the case to shove forward after the slide comes into battery.

There is a lot of things going on in this 3 dimensional action.

We also all need to look at the chamber specs as we assume there is a tight fit. I think the rear of the chamber on the prints is a bit larger than the case dimensions.

This post should go in the other thread but I will put it here.

[1874Sharps]

Joe,

I am not sure you are understanding what I am saying.

[StarMetal]

Joe,

I am not sure you are understanding what I am saying.

Oh I understand. I just don't think that was the idea behind it is all.
Certainly the match 1911's aren't at all like that.

Joe

[35remington]

"Depth from chamber end "step" to barrel hood .749"
Gap from barrel hood to breach face on slide .202"

Danski, something don't add up.

The depth for the chamber shoulder to hood don't look right. If .749" was the actual depth of the chamber from shoulder to hood, your cases would be sticking out of the end above the hood about 0.14" with a .888 case in the chamber which is a little much. Further, the hood being two tenths of an inch from the breech face would have an almost ridiculous gap from hood to breech visible when the gun's in battery. I could believe twenty thou but not two hundred thou or two tenths inch.

This would look so strange nobody would shoot it. It wouldn't make it out of the factory, either. The hood/breechface fit can't be that sloppy.

Could you remeasure and try again?

The chamber shoulder to hood measurement may come up a little too short, period. On this particular Colt barrel in the picture, the distance from hood to chamber shoulder is .892" which is seemingly too short, but since the headspace measurement's from chamber shoulder to breechface, and since the hood/breechface gap is around 0.018" as fitted by the Colt factory, the headspace is around 0.910." If your gun comes up .952" that's way, way outta spec, which is why I'm asking for a remeasure. A gun with that much headspace should have never been sold. Also, the other two measurements don't make sense either.

When fitting my Bar Sto barrels, they come long in the hood measurement and I have to dress the hood back to a zero clearance (or near to it) fit of the hood to the breechface. Colt doesn't have time to be fitting barrel hoods to individual guns so they are slightly short in the chamber shoulder to hood dimension and this works fine and saves time.

In this gun, a case head above flush (contrary to the dicta that the case head must be flush with the hood to chamber fully) a small amount is still properly headspaced and is not "too long."

On topic:

In terms of headspacing, it's the hook on the extractor that will do it if it occurs. The headspacing surface must be strong enough to resist the firing pin blow and prevent the case from going deeper in the chamber, and "side tension" from the extractor won't do to headspace the round....it's got to be a stop. Thus the hook is what is determinative in headspace if it does occur.

Just as the chamber and cases have tolerances, so does the extractor hook distance from the breechface. It has to be some distance from the breechface so the rim can slide up underneath it easily on its way to the chamber. Since the rim approaches the breechface at an angle (the breechface should be angled as well) and that angle varies with the magazine used and its release timing and the length of the ammo, the extractor/breechface distance also has to have tolerances. If it's too small the angled rim cannot get under the extractor smoothly and the gun will be a jam-o-matic.

This is the reason it's a common reliability trick to put a slight radius on the bottom of the hook.....to give a bigger area or window to allow the case to slide up smoothly. The breaking of the corners also supposedly makes it less "grabby."

On edit:

Another topic for 1874......headspace may have nothing to do with the propensity towards blowing the case head in high pressure cartridges as long as it is within acceptable limits. If the headspace is perfect, the case may still blow out if the barrel ramp is moved too far forward into the chamber by some zeeb with a dremel. The barrel ramp is the weak point for automatic pistol cartridges. High pressure cartridges minimize the barrel ramp (hear of the "fully supported barrel?") to better support the case head.

I think, properly stated, that you may get away with a little more deepening of the barrel ramp into the chamber with the 45 due to its lower pressure, but 45 case walls ain't that thick themselves despite the low pressure. Minimal exposure of the case in the barrel ramp cut is always better assuming the barrel ramp angle and the frame ramp angle are otherwise in spec, and that the necessary gap between frame ramp and barrel ramp exist.

I don't think that the "hammering" of the case head against the breech from headspace slack has a whole lot to do with gun longevity. A gun fired with, say, NATO ammo in a GI issue Beretta gets hammered its entire lifespan and I doubt it leads to failure as opposed to a round with zero headspace. It is the sudden onset of pressure itself that cracks slides, especially around the sharp junctures in the area of breechface and ejection port, which are stress risers. When slides crack, it's usually around the breechface. IMO zero headspacing won't help this.

Excessive headspace in rifles destroys the rifle because the case head separates, allowing the high gas pressure to escape, working against the rifle and destroying it. If the case head doesn't separate the rifle is not harmed. Case head pressure against the breech is also a different animal, as 62,000 psi in a rifle is a lot different than the 35,000 psi of a 9 or 40 and the 19,000 psi of a 45.

I like this kind of discussion better, I must say.

[danski26]

I'm sorry for the mistake in measuring and in nomeclature. My measurements should be;

Chamber step to barrel hood .910"

Gap between the cartridge head and the breach face when place under the extractor is correct @ .021"

I measured the chamber from the step to the portion of the barrel that is not extended into the hood. I then measured this portion to the breach face when the hood was against the breach face and the barrel was in battery. But this measurment was not correct as the barrel bushing was not in the pistol and the barrel was tilted upward causing a larger gap.

So.....On my 1911 for the case to contact the step in the chamber it would have to be at least .889" long. Which is very close to average.

Tomorrow, if I have time, i will break out the pin gauges and measure the diameter of the of the barrel at the chamber step and compare it to a loaded rounds case mouth diameter.

[scrapcan]

I disagree on the side tension of the extractor not being able to hold the case for firing. you can take a properly set extractor (clearanced for feed both on hook and radiused corrrectly) and you can fire a primed case without the barrel in place. I had a retired USAF armorer show me this in a gunshop he owned. I have seen it happen and it takes no more force to fire a primed case than it does to fire a loaded round in the chamber. The case will eject to the side due to the force of the extended floating firing pin.

Edited to ad disclaimer: If you do the follwoing proceedure as it was shown to me you do it on your own volition as the sole responsible party for our actions. It was shown to me and i do not recommend it.

Here is what Mr. Bresnahan showed me ( hes adi I could call hima nything except by his rank as I was not and not military, I respect his wishes as he is now deceased). If you are inclined to try this be as safe as you can. Try this in a safe place with ejection port faced away from you and barrel pointed in a safe direction. take barrel, recoil spring and guide out of firearm. put piece of primed brass under the extractor and put slide into firing position. Hold slide with off hand w/ ejection port in safe direction (away from you and down) muzzle in safe direction or in firing trap. use trigger to drop hammer. I will bet you it will fire the case. In this instance there is nothing holding this case except the extractor hook and side tension to keep it on the breech face. Was it designed to do this , NO. does it do it YES.

may not mean a thing to the thread here but it is true the side tension will hold a case long enough for firing pin to strike the primer and set it off.

[StarMetal]

Any good book or smithy on building the 1911 will tell you that there is a proper tension for the extractor. The cartridge isn't supposed to drop from it's grasp when you have the slide off the gun and checking it for that.

Joe

[scrapcan]

Joe

i agree with your statement and is the reason I put it in my post. T here is more to fitting an extractor than radiusing the bottom of the notch for the case to feed, things like fitting of the nose for extractor groove, fit the hook for rim thickness, tension setting, fitting the rear where the firing pin stop plate resides (and fitting a firing pin stop plate). Many do not know this as they just buy the drop in parts and assume that is the way it is supposed to be and that is all they need to do.

I learned alot from the gentleman mentioned above and one thing is if you are going to work on a firearm you better study it, shoot it, take it apart and study it, put it back together and study it, then you might be ready to do something. The above test was part of his showing me something I thought I knew, I found out I was wrong. The extractor will hold a case for firing.

[BLTsandwedge]

See, this is why I have revolvers......

Tom

[danski26]

A few more measurements on my springfield 1911;

The diameter of the step in the chamber is .451-" (there is a very slight taper, the .452-" will pass the step by .001"-/+)

The depth of the chamber from the breach past the step, to the rifleing total is 1"

I measured some Winchester Ranger 230 gr +p ammo and the case mouth averages .472"

So in my 1911 there is no problem with this ammo having enough case mouth diameter to contact the step in the chamber.

At least in my 1911 I would say that the only time the cartridge headspaces off the extractor is at a length of less than .889", AND the full diameter of the bullet (.451" or larger) is less than 1" from the cartridge base.

Kinda interesting....depending on the case and bullet there are three different ways the cartridge will headspace. I learn something new every day!

[35remington]

As with most things, there's a specification for the distance the extractor hook must be from the breechface if the gun's within spec, just as headspace must have a minimum and maximum dimension. Given this thread is about measuring, this shouldn't be surprising.

With an acknowledgement of 1911 specifications from m1911.org:

For USGI M1911A1's, the extractor hook/breechface "gap" will be

1. 0.0880 +/- 0.0095 inch with the extractor fully forward, and

2. 0.0805 +/- 0.0100 inch with the extractor fully rearward in its tunnel.

Since cartridge case rims are in the vicinity of .038" to .040" or so on the few I've just measured, when the rim is bearing on the extractor hook the distance from case rim to breechface should be in the vicinity of about 0.045" to 0.050" if the extractor is forward in its tunnel when you're measuring the rim/breechface distance. When headspacing on the extractor, the extractor will likely be driven fully forward in its tunnel by the blow of the firing pin....so the fully forward dimension is most relevant. It is not hard to see that since the rim/breechface gap is toleranced to be larger than the headspace measurement as a consequence of extractor hook distance from the breechface, most of the time it's likely to headspace on something other than the extractor. That is, if things are within specifications. Most of the time 1911's are, but I suppose it's occasionally possible to botch things up with a super short case.

This isn't the norm, though.

"Gap between the cartridge head and the breach face when place under the extractor is correct @ .021."

If your gap is .021" I wouldn't call that correct. Something is out of spec or the measurement is off.

Firing the primered cartridge without a barrel looked to be the result of extractor tension and the extractor hook. I hope I understood you correctly.

You said this:

"In this instance there is nothing holding this case except the extractor hook and side tension to keep it on the breech face."

With the tension holding it in place until the rim hit the hook, headspacing and firing the round.

[scrapcan]

That is what I wrote. There is no headspace dimension as the headspace is set by the breech face and chamber dimensions. What I am saying is that even if headspace and extractor hook give generous clearance (too long or too much headspace if chamber is too long) the round will still fire as it is initially held with side tension long enough for firing pin to strick primer and set it off. I was also told by the same gent that if you take the hook off and have proper tension the primed case will still fire. He was not willing to ruin an extractor nor am I. I just take his word for it.

I like the 1911 platform and think it works on a whole lot of fronts, even those for which the design may not have taken into account.

[Rodfac]

At the risk of throwing another dog into the fight, I'll say this. Ten years ago, doing some load work up for a Colt 1911 in .40 S&W, (see the pic below), I was using Ken Waters' published work as a guideline. His "Pet Load" column in July of '91 covered his experimentation with a 10 mm Delta Elite converted to .40 S&W.

Lacking the necessary .40 S&W brass to begin, he shortened 10 mm brass, then fired one entire magazine of it, mixed every other round with full length 10 mm rounds, through the 10 mm barrel. He stated that the 10 mm case headspaces on the case mouth as does the .40 S&W. Using the shortened 10 mm brass, the "unsupported short cases" had .142" of excess headspace. They all fired and Waters said they made a surprisingly small grouping on his range.

Since both the .40 S&W and 10 mm cases show only .001" and .002" of outside taper, respectively, I conclude that the .40 was held in place in the chamber only by the extractor hook, but nevertheless, fired successfully.

It's not a practice I'd like to make a habit. Regards, Rodfac
PS: My copy of the article was reprinted in the 5th Supplement to the Third Edition of his fine book, "Pet Loads" as published by Wolf.

http://i261.photobucket.com/albums/ii64/Rodfac/Handguns/40SW1911.jpg

[Lloyd Smale]

ive got two 1911s i shoot competition with a colt gold cup and a kimber gold match. I feed both mixed brass and never trim 45 brass. They both are a 100 percent reliable and shoot loads they like under an inch at 25 yards so bottom line is i dont give a **** where theyre headspacing

[scrapcan]

loyd,

I agree with you. If it is reliable and shoots to your expectations that is what counts. That was the end product of the old USAF armorers' lesson to me. Make them work and make them work every time especially if someones life is dependant upon it.