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Old July 6, 2000, 12:49 AM   #1
CassandraComplex
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I am wondering why I can't take a .40 caliber brass and load it "really" long, with, say, 200gr bullets, and shoot it out of my 10mm.

Can anyone give me specific reason why I can't do this?
Something other than "your gun will blow up" would make me very happy. I would appreciate specific details on what will go wrong.

I can't see why....especially if I load it with a light powder charge....why I cannot do this?


I am just thinking about this for an economical and possibly emergency situation.
I would not make a habit of it, (but it is tempting because .40 brass is so cheap and easy to find).

It seems to me with the long bullet, like a 200gr bullet, that it would give me enough bullet length to load the round long and have plenty of bullet left to crimp.
Also, if I used a light powder charge, I don't see why I could not load the length of the cartridge somewhere between 10mm and .40 length for a happy medium length cartridge.

Thanks for the advice!
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Old July 6, 2000, 03:24 PM   #2
STRIDER
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IN a pinch, MAYBE. There are a couple of issues:

1-The cartridge is supposed to headspace on the shoulder of the brass case. The 10mm case is much longer than the 40. The shoulder of the 40 will not come even close to the headspace point of the barrel.

2- The 10mm brass is much stronger and thicker around the web area. Also, most 10mm guns do not have a supported chamber. The 40 is much safer with a chamber which provides full support to the case head, mandatory with 10mm loads.

I would highly reccommend against the practice, ever.
HTH


[This message has been edited by STRIDER (edited July 06, 2000).]

[This message has been edited by STRIDER (edited July 06, 2000).]
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Old July 7, 2000, 01:03 AM   #3
Sub MOA
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Regarding Strider's reason number 1: "The cartridge is supposed to headspace on the shoulder of the brass case."...NOT quite right. The cartridge DOES headspace on the MOUTH of the case. Regardless of semantics, he is correct in advising against this practice.
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Old July 7, 2000, 08:19 AM   #4
WESHOOT2
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Actually, most guns 'headspace' on the extractor.

------------------
"All my ammo is factory ammo"

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Old July 7, 2000, 11:41 AM   #5
STRIDER
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I was intentfull using the "Supposed to"phrase. Ideally the cartridge should headspace on the shoulder.

In reality, it headspaces on the extractor as weshoot2 pointed out. This is due to the chamber depth tolerance stacking up with the brass length tolerance.
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Old July 7, 2000, 02:35 PM   #6
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Strider, I think you may have misunderstood (in part) CC's question - he is not asking, contrary to his specific wording, about using 10mm "loads" (i.e. powder measure), I don't think. Therefore, using .40 s&w loads, the thickness of the brass is irrelevant UNLESS the bullet is seated too deeply. BUT this deep seating problem is specifically overcome by the fact he will seat the bullet much farther out, to come close to the OAL of a 10mm round. And since, as pointed out, in the Glock's controlled feed, headspacing is accomplished by the extractor, I don't see any problems with this as long as you watch for sign of overpressure. HOWEVER, my advice is worth 2 cents or less, as I am in no way an expert.

[This message has been edited by Futo Inu (edited July 07, 2000).]
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Old July 7, 2000, 05:07 PM   #7
Bud Helms
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Hmmm. Headspace on the extractor, eh? So, this fiction persists? I guess every loading book on the shelf, reamer makers like Clymer, and all the Gunsmiths in the US are wrong then?

Straight walled, semiauto pistol cases headspace on the case mouth. Don't you think?
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Old July 7, 2000, 07:10 PM   #8
HankL
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sensop, They will fire if held by the extractor. After that..... ??? and just for you
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Old July 7, 2000, 07:42 PM   #9
WESHOOT2
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In most guns the tolerances in the chamber are large enough that the mouth will never get near the end of the chamber.

Try this; remove the slide and slip a cartridge under the extractor. See if it holds it firmly against the breechface.

Don't try this at home! I've fired 9mm from a 41AE. Headspace?

(maybe I'm an example of empty-headspace)

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Old July 8, 2000, 07:01 AM   #10
Bud Helms
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Doesn't matter if they will fire held by the extractor. That's not headspace.

"... I guess every loading book on the shelf, reamer makers like Clymer, and all the Gunsmiths in the US are wrong then? ..."

I don't see an answer to this question. Are you saying that these people have it wrong and have perpetuated a myth for ... how many years? I'll change my supposition statement to read "... most Gunsmiths ..." or " all reputable Gunsmiths ...". When did the realization come on you that the two points between which you make the measurements for headspace is from the surface of the breechface to the contact surface of the extractor? At what point in your reloading experience did you decide, "Well, these reloading manuals and pistol barrel makers are just wrong."?

This discussion has been held here before. By your definition, a Remington 700 in .30-'06 headspaces on the extractor. You think so? I guess a .308 Winchester round has the same headspace as a .30-'06 Springfield? They both are held against the breech face (bolt face) by the extractor!

Why don't we just take a 10 mm cartridge and just chamber (jam?) it up in a 40 S&W chamber? They both headspace on the extractor with identical dimensions, right? ... Yeah, I thought not.



[This message has been edited by sensop (edited July 08, 2000).]
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Old July 8, 2000, 09:19 AM   #11
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Hello there sensop.

I never said "every loading book on the shelf, reamer makers like Clymer and all the Gunsmiths in the US are wrong."

I also never made any reference to rifles either. Nor did I say or reccomend measuring between the breechface and extractor to get a headspace measurement.

Actually in most pistols and rifles the extractor does not hold the round back against the breech, there is some float between the case rim and the claw.


The point at which I formed my opinion was when I MEASURED several chambers and MEASURED lots of brass and ammo both factory and reloaded. Then I READ the SAAMI standards for chambers and ammunition. After that I actually chambered a few barrels and loaded some ammo. Anyone who does the same thing will come to the same conclusion.

My understanding of the term "headspace" is that it is the distance between a reference point in the chamber, to the breechface.

The issue here is very simple to understand:

The chamber has a nominal depth with a plus variation. Usually, actually almost always, the chamber is cut a little deeper than the minmum dimension. In a production gun, this can be quite a bit.

The brass case also has a 'nominal' length dimension, which happens to be shorter than the nominal length of the chamber. Usually it is manufactured slightly shorter than the maximum tolerance. Add to this the fact that most pistol brass shrinks some in length after firing and you have a situation where the end of the brass case does not reach the shoulder of the chamber.


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Old July 8, 2000, 09:30 AM   #12
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Futo,
Good points.
FYI, I have shot the 40 loaded long for about 2 years in IPSC. The difference in my situation is I shoot a barrel chambered to 40 headspace dimensions. I have the rifling leade reamed to accomodate the longer bullet length

At 10mm lengths, even as short as 1.200, the pressure in a 40 is greatly reduced. However i still think a supported chamber is mandatory for the 40.

Controlled round feeding has nothing to do with headspace.
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Old July 8, 2000, 09:16 PM   #13
Bud Helms
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STRIDER,

"I never said ..." ... wanna gimme a break, here? Ever heard of a "logical conclusion, drawn from assertions made"? Did you think about the examples I used? Because everything in the chamber beyond the headspace measurement point is somewhat undefined.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>My understanding of the term "headspace" is that it is the distance between a reference point in the chamber, to the breechface.

The issue here is very simple to understand:

The chamber has a nominal depth with a plus variation. Usually, actually almost always, the chamber is cut a little deeper than the minmum dimension. In a production gun, this can be quite a bit.

The brass case also has a 'nominal' length dimension, which happens to be shorter than the nominal length of the chamber. Usually it is manufactured slightly shorter than the maximum tolerance. Add to this the fact that most pistol brass shrinks some in length after firing and you have a situation where the end of the brass case does not reach the shoulder of the chamber.[/quote]

I agree, the issue here is very simple to understand: headspace is the distance between a reference point in the chamber, to the breechface. The reference point in the chamber is not the extractor claw in this case, but the case mouth.

The last two paragraphs in the quote are, I believe, mostly true. They are also irrelevant to the definition of headspace.

I don't claim headspace to be some inviolate dimension which, when exceeded, will turn your gun into a puff of smoke. That's why bottle necked rifle cartridges are fire formed and reloaded with neck sizers or shoulder bumped. Because there are variations in chambers, brass and dies. The chambers of straight walled auto pistols are chambered within in a SAAMI range of dimensions just like rifle chambers. I agree.

All this does not change the fact, not opinion, that the definition of headspace for these pistols is breech face-to-case mouth. You and I can measure chambers and reloaded rounds 'til the cows come home. That won't change.

The extractor claw helps keep the cartridge snug against the breech face, so that it will remain within the headspace dimension of the breechface-to-chamber dimension, when in battery. That is not the same thing as headspacing on the extractor.

*******************

My anal retentive side is now in full tactical mode. I am withdrawing to remedicate and contemplate the usefulness(?) and frustrations of arguing logic with minds-made-up. Peace.




[This message has been edited by sensop (edited July 09, 2000).]
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Old July 9, 2000, 01:03 PM   #14
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Sorry Mr. Sensop, but you are wrong.

If this is just an exercise in semantics for you, pay closer attention. My first post said "is supposed to headspace". I have never mentioned any other definition to the term "headspace" than the one we seem to agree on.

I will thank you not to attribute broad sweeping generalizations to me. Also, I do not believe you made a logical conclusion from my assertion.

Actually the chamber dimensions are very well defined in several areas other than the headspace point. Diameter, taper, throat, to name a few.

In most, if not all, situations the extractor claw holds the case rim tight against the SIDE of the breechface, not back. In the 1911 for example, a properly fitted extractor has a small amount of float or clearance(which is taken up when the slide moves rearward) before it starts to pull the case out of the chamber. Headspacing on the shoulder will occur regardless of whether there is an extractor in the gun.

Perhaps if I were to rephrase as follows you can stop being frustrated and get off medication.

"Headspace is intended to properly align the cartridge in the chamber, and keep the cartridge from going too far forward, ie; the bullet and case entering the rifling.

The 10mm cartridge is designed to headspace off the shoulder of the case. What this means is the end of the case mouth should rest on the shoulder of the barrel chamber when the case head contacts the breechface. This, of course, when the gun is in battery.

In practice however, the distance from the breechface to the chamber shoulder is longer than the length of the case.
Thus, the extractor claw limits the forward movement of the cartridge.

The case of the 40 is significantly shorter than that of a 10mm. A 40 case with the bullet loaded to 10mm(or any other) length will not be able to headspace correctly on the shoulder in a 10mm chamber."

If you want to argue logic, feel free to start a new thread.
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Old July 9, 2000, 02:21 PM   #15
Bud Helms
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"... I do not believe you made a logical conclusion from my assertion. ..."

I believe that I'm communicating poorly.

"... I will thank you not to attribute broad sweeping generalizations to me."

I also believe that this exchange is bordering on becoming personal. So, since I started this and it's getting nowhere, I choose to end my part. No more to say. Let's discuss again sometime. No hard feelings here.

sensop

...



[This message has been edited by sensop (edited July 09, 2000).]
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Old July 14, 2000, 09:31 AM   #16
Clark
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I have noticed that cases will headspace on the extractor. It may not always, and I haven't fired a primer to see if it hold it well enough to shoot.
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Old July 14, 2000, 02:28 PM   #17
JackFlash
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Answer to the original question, "Can I shoot a 40 S&W case in a 10mm cal. gun?" . . .

NO, NO, NO . . . !!!

Re: the raging semantic argument in here.

"Headspace" is a verb. "The headspace" is a noun which describes the function of the verb "headspace." Granted, nouns are often used without articles, but then you're getting into dialectical variation and Stanley Fish's notions of convention and the authority of the discursive / interpretive community. But we won't go there without being provoked.

In a rimless semi auto case -- like the 40 and the 10mm -- the case *headspaces* (verb) on the mouth of the case which rests on a rim at the end of the chamber, just short of the lede (sometimes spelled leade). The lede is the distance between the shoulder of the bullet and the beginning of the rifling. This region is called the throat.

A check of case spec's for the 40 and 10mm show a case mouth diameter of 0.423" and a bullet diameter of 0.400". The 0.023" nominal dimension of the case-mouth rim is what headspaces the case. The extractor MAY hold the head of the case against the firing pin and bolt, but that's not headspacing.

Accordingly, a longer bullet "loaded long" MAY in some manner rest against the headspace rim in the chamber, but it's not going to headspace the cartridge and you'll get gas blow-by which will erode the headspace rim and the lede.

Moreover, working pressures in ammo are sensitive to nominal case capacity as it is affected by seating. The smaller the capacity, the higher the working pressure. Heavier bullets, because they create more resistance, create higher pressures. This is whey mfg's warn about seating depth, bullet length, and case capacity.

Double base powder requires pressure to function. Pressure generates more pressure in an exponential ratio. 2x powder = 2 energy, but 4x powder MAY = 8, 16, or even more energy depending on the characteristics of the powder.

Headspace affects pressure. Because a 40 case won't headspace in a 10mm, you're whistling in the dark with one leg in Hell with regard to pressure and pressure spike characteristics. Because the bullet is not correctly headspaced, there's every possibility that it can become canted in the bore sufficiently to drive working pressures to dangerous levels.

Semi-auto chambers are not fully supported. The feed ramp cuts under the web of the case, and the breech is flared to accomodate reliable feed. Take your semi auto barrel out of the gun and insert a live round. Notice how loose it is and how the feed ramp at 6:00 O'clock cuts under the rim and into the web portion of the case.

Glock extends the feed ramp and breech flare to the maximum SAAMI tolerances which is why Glocks dont jam. BUT the case is unsupported. If the case is "headspaced" by the extractor then you're really asking for trouble. All that stands between you and the tons of gas in the chamber is a brass case that is designed to seal against the headspace rim and the sides of the chamber. The bolt headspaced against the case head ensures that the seal in the chamber is precise. The extractor won't accomplish this seal of the case in the chamber.

There's a reason why mfg's warn repeatedly about using "the correct caliber ammo in modern guns in good repair." The warning is to ensure that all the physics of this ignited nitro-cellulose and nitroglycerine in double base pistol powder moves out of the barrel past the muzzle and not around a catastrophic case failure and into the breech of the gun.

Admittedly more than two cents, but it seems warranted.

[This message has been edited by JackFlash (edited July 14, 2000).]
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Old July 14, 2000, 06:42 PM   #18
Bud Helms
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Jackflash, ... boy, you're in trouble now.

...
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