Talk:Headspace (firearms)

Go, No-Go

I changed minimum and maximum to "go" and "no-go". Besides the more common terminology, a gauge made to "maximum" chamber dimensions ought to chamber. A "no-go" is just a bit larger than the maximum chamber dimensions, and represents the smallest size that will not chamber. 66.173.192.96 01:18, 19 December 2005 (UTC)

If any page needed a diagram, this is it. I've read that three times and still don't understand it...

Belay that. I figured it out, so I made and added a diagram. Xmastree 15:49, 14 January 2006 (UTC)

I find this article confusing, even with the diagram (thanks, Xmastree). Is it possible for a someone with a strong grasp of the topic to go through and totally rewrite it for the layperson? 68.232.64.116 23:23, 12 December 2006 (UTC)

Can we get another diagram depicting a cartridge that headspaces on the rim? I believe there are also come cartridges that headspace on the extractor. SquareWave 02:57, 24 March 2007 (UTC)

Headspace is typically either rim thickness (for rimfire like .22 and rimmed centerfire cases like .303), distance from datum line on the shoulder to case head surface (rimless necked cartridges like .30-06), or distance from case mouth to case head surface (rimless straight cartridges like .45 ACP). If there are any that headspace on the extraction groove, I'm not aware of them. But I agree that diagrams of these types of headspace dimensions, and some examples of headspace gages, would be very informative. Lihan161051 (talk) 15:47, 28 July 2009 (UTC)

I too find it confusing. I think the main problem is that it goes right into discussion of "go," "no-go," and "field;" wothout actually explaining what they are. Scoldingmonkey 19:50, 14 February 2007 (UTC)

Just reworded the article. How about it now? —Thernlund ^{(Talk | Contribs)} 01:15, 15 February 2007 (UTC)

Much, much better. 66.117.248.200 17:22, 20 February 2007 (UTC)

Good content rewrite, covered the basics rather well.  ;) It might be instructive to add a bit more discussion on why headspacing is a critical safety check, especially for excessive headspace which can cause a case head failure if it's far enough out of tolerance .. especially if it's possible to find good images of a cartridge where the case head has separated and/or subsequent damage to the firearm. Brownell's might have some good "how and why" content to link to, and some examples of headspage gages. (Minor nitpick on spelling -- "gage" is used in some specialties, and by some gunsmiths in particular, to distinguish it from "gauge", although that's old school and possibly archaic usage.) Lihan161051 (talk) 15:36, 28 July 2009 (UTC)

Suggestions for "how and why" content: [1] and [2] Lihan161051 (talk) 15:43, 28 July 2009 (UTC)

The Headspace Diagram is incorrect for headspace location on the rifle cartridge. The headspace locates from a diamter on the cone at the front of the cartridge, that is the shoulder, not at the point where the shoulder meets the neck. Can someone fix this graphic?Metafortis (talk) 13:41, 1 April 2016 (UTC)

Move

The term "Headspace" is used to refer to several things, perhaps we should move the article to "Headspace (firearms)" and make this page a disambiguation link. If nobody objects I will do this in a few days. Sjschen (talk) 05:34, 25 May 2008 (UTC)

Field Gauges

For current or former military calibers, a "field" gauge can also be used. The "field" gauge is designed to take the place of the "no-go" gauge in military firearms, and functions in the same way. Military firearms are designed to withstand higher pressures. As such, a greater tolerance in the firearm's headspace is acceptable, and the "field" gauge takes into account this greater tolerance. "Field" gauges should be used only on military firearms, and not on commercial firearms. Headspacing a commercial firearm with a "field" gauge can create an unsafe condition. (Military arms are not designed for higher pressures than civilian arms. The Field gauge does not replace the No-Go Gauge. The No-Go Gauge is used by a manufacturer or gunsmith to tell him he has or has not reached maximum allowable chamber depth and the firearm will be safe to fire. The Field Gauge indicates if a chamber is under the maximum allowable chamber depth/headspace or exceeds it. There is a general misunderstanding of this use of No-Go Gauge for reaming new chambers and the Field Gauge for measuring excessive headspace.

Any firearm that locks on a "field" gauge is unsafe to fire, and should be checked by a trained gunsmith.

Guns that fail to lock on the "go" gauge may simply need cleaning, especially at the bolt face, as build-up may occur on this surface and this buildup can cause problems in chambering a round without stressing the brass.

Headspace gauges are designed to indicate simply whether a firearm's chamber is in tolerance. There can be other types of gauges that measure exactly how over or undersize a chamber might be.

I moved the preceding unreferenced discussion of field gauges out of the article until reference citations may be found to transfer appropriate sections back into the article.Thewellman (talk) 18:54, 12 March 2010 (UTC)

.22 rounds

This article currently uses an image of a .22 Long, .22 LR, and .22 WMR cartridges with a caption suggesting that all 3 can be fired in the same gun because they all headspace on the rim.

Rimmed .22 cartridges headspace on the rim, allowing cartridges of different overall length to be fired in the same gun.

While both .22 Long and .22 Long Rifle ammunition can be safely fired in many firearms, the .22 WMR is not only longer, but is also wider, than the others. .22 WMR cannot be fired in guns chambered for .22 Long and/or .22 Long Rifle.

If possible, an image showing just the .22 Long and .22 LR cartridges, perhaps also with the .22 Short, should be made and placed in the article. Another suitable substitution would be the .38 Special and .357 Magnum cartridges, both of which also headspace on the rim, and both can be fired from revolvers chambered for the longer .357 Magnum cartridge. Jersey emt (talk) 04:29, 12 August 2010 (UTC)

Replaced with comparative image of .22 short, long rifle, and CB cap.Thewellman (talk) 04:38, 18 September 2010 (UTC)

Actually .22 WMR can be fired from the same gun that fires the .22 Long and .22 Long Rifle. However, they cannot use the same chamber. Ruger used to manufacture a .22 revolver which was supplied with 2 cylinders, one of which chambered the .22 Long and .22 Long Rifle and the other chambered the .22 WMR. 86.150.137.204 (talk) 16:43, 8 August 2014 (UTC)

That is only partially correct, and suggests an incorrect conclusion; because headspace is a function of chambering. The two cylinders had different chambering specifications. The revolver bore diameter was slightly larger for the .22 WMR. I had an opportunity to fire one of these revolvers and found the accuracy of .22 Long Rifle cartridges disappointing in the oversize bore.

A shooting companion once purchased the .22 Long Rifle version of a non-convertible firearm also available chambered for the .22 WMR. Since he could not chamber .22 WMR cartridges in his .22 Long Rifle firearm, he decided to rechamber it for the .22 WMR. He discovered the pilot section of the .22 WMR chambering reamer (intended to align the reamer within the bore) was too large to be inserted into the .22 Long Rifle bore. With more ingenuity than common sense, he reduced the diameter of the pilot section of the .22 WMR reamer to accomplish the rechambering. Excessive pressure created by firing .22 WMR cartridges in a .22 Long Rifle bore distorted the firearm action until it was non-functional.

He was fortunate the firearm design avoided potential injury from a catastrophic failure. No useful purpose will be served by encouraging Wikipedia readers to believe the .22 Long Rifle and .22 WMR can be fired with the same headspace. Thewellman (talk) 18:26, 8 August 2014 (UTC)

go no go gauge

It might be helpful also, if go no go gauges were related to threading, as in screws and bolts/nuts. just a suggestion. Ghosty1 (talk) 04:59, 15 January 2011 (UTC)

Reference citations

This article has been expanded by user 123.200.238.50 for clarification and to include additional information. The additional information requires reference citations. An alternative definition of headspace is especially confusing in the existing page layout. I suggest moving the information regarding other chamber dimensions to a new section at the end of this article or possibly to another article (to be identified in the Headspace disambiguation page) to avoid confusion about the single dimension along the bore axis, at a specified radius perpendicular to that axis, fitting the definition of headspace in the cited reference.Thewellman (talk) 07:54, 19 March 2011 (UTC)

Reference citations requested above were provided (in non-standard format) by user 121.91.96.140. Unfortunately, while these references discuss similar subjects, they do not confirm the statements they follow. I am moving these unreferenced statements to the talk page with a summary of the inconsistencies until more accurate reference citations are provided. I suggest a more informative reference citation format such as:<ref>{{cite web|url=|title=|publisher=|accessdate=}}</ref>
Thewellman (talk) 17:50, 26 April 2011 (UTC)

1st unreferenced section

Have a competent person conduct these checks with the proper gauges prior to using any second-hand firearm for the first time. If you don't, then it may well be the last time you pull a trigger.

Citation: http://browningmgs.com/Malfunctions.htm

The citation provided refers specifically to Browning machineguns, and makes no mention of being "...the last time you pull a trigger."Thewellman (talk) 17:50, 26 April 2011 (UTC)

2nd unreferenced section

Headspace for a firearm made for rimmed ammunition is the free space that remains between the rim-stop and the bolt face (less the thickness of the rim) once the cartridge is fully within the chamber and the bolt is fully home and locked (if it is a breach locked action). The purpose of correct headspace is to ensure safe reliable loading and consistent accuracy.

Citation: http://www.forsterproducts.com/store.asp?pid=24834

The citation provided is an advertisement which does not support any definition of free space rather than a single total space of the standard definition.Thewellman (talk) 17:50, 26 April 2011 (UTC)

3rd unreferenced section

If the case is too short then the cartridge can move ever so slightly up, down and sideways within the chamber. Imagine the rim-stop has some grit or sand specks fouling the small step at the rear of the chamber. On closing the bolt on a short case, this grit can cause the cartridge to cant in the chamber, putting the point of the projectile off center to the bore. On firing the projectile starts out engaging the rifling with less than optimum attitude, which translates to a broader spread of the points of impact compared to the point of aim. Even when the rim-stop is clean a short-case cartridge with a flush or recessed primer can cant as it is not fully supported at the neck and dips down slightly due to gravity. Target shooters have several ways of eliminating, or at least, greatly reducing these error inducing characteristics. This is the 'art' part of the 'science' of target shooting.

Citation: http://www.forsterproducts.com/store.asp?pid=24834

Again, this advertising reference refers only to headspace gauges and says nothing about 'art' and 'science' or the accuracy impairment potential of cartridge misalignment. The issue of misalignment is more directly related to cartridge diameter rather than headspace. It may cause confusion in this headspace article and might better be placed in the handloading article.Thewellman (talk) 17:50, 26 April 2011 (UTC)

20x110mm Hispano cannon, US reliability issues vs headspacing

I'm curious about the US made version of the Hispano-Suiza HS.404 20mm cannon used during WWII (this is the US copy of the gun the British used in their fighter aircraft). Apparently, the UK-made gun served as an excellent weapon with great reliability, but the US gun never entered wide-spread service due to appalling reliability. The commonly stated reason for this is that the US version, the M2, for some reason was given a longer chamber, which cause the primers to be lightly struck, not igniting the round. The case appears to be headspaced off the shoulder, as it is rimless and beltless, and has a strong but shallow shoulder. If one were to make a chamber several millimeters too long, so that that the round sits so far into the chamber that the striker can't hit the primer properly, isn't that a headspacing issue? I don't see anything about that on this page, other than that the CIP claims that headspace doesn't need to be tested because "the round will fail to fire" (don't recall if that was from excessive or too little headspacing though). Seems like it could be more clear (both on this page and the HS.404 page). If the headspacing is too LITTLE, the round will protrude from the chamber and perhaps rupture? How is it that the bolt can even close totally? Would the headspacing have to be REALLY off to prevent that? And too MUCH headspacing leaves the rear of the case unsupported? It says that it can cause the primer to be blown out, or the rear of the case can seperate...wouldn't the case be blown back against the bolt face by the pressure of the explosion? Or does it stick in the chamber due to being forced outwards at high pressure, yet the rear isn't being supported by the bolt face, and so can separate from the rest of the case? Is too MUCH headspace dangerous, or does it just mean the cartridge won't go off? Why didn't the US have problems with 20mm cases bursting if their chamber was "several millimeters" too long? I'm confused as to the dangers and reasons for these dangers, of too much and too little headspacing, respectively..45Colt 19:28, 1 September 2015 (UTC)

• The issues you discuss are only partially related to headspacing; and size differences of the weapons involved may impose different concerns. Vehicle-mounted weapons may have steel cases of significantly greater strength than brass small arms cartridges. Twenty millimeter ammunition often fires a steel projectile with a copper rotating band; and the depth to which the cartridge enters the chamber may be controlled not by headspace on some portion of the brass cartridge, but by the point at which that copper rotating band reaches the rifling. The cartridge might enter the chamber more deeply as the throat of the rifling was eroded by heating during rapid fire. This might theoretically be corrected by increasing the frequency of barrel replacement, specifying barrels of more durable alloys, and/or extending the length of travel of the bolt and/or firing pin. Some blowback weapons do not require a locking bolt, and rely upon the mass of the recoiling bolt to hold the action closed until the projectile clears the barrel.

Your questions about consequences of headspace variation imply your knowledge of the subject may be limited, and cast doubt on the validity of your edits without reference citations. I hope finding the requested reference citations will lead you to the answers to your questions. Thewellman (talk) 04:30, 2 September 2015 (UTC)