All this headspace information
All this information about headspace issues and broken cases concerned me to the point where I was fearful to go to the range with my refinished (but unheadspaced):yikes:
No4 Mk1. Well I went today and shot 15 rounds of Winchester ball and to my great relief the gun didn't explode and I came home with my face and fingers.
I also was able to shoot my fathers IBM M1 Carbine which has neither been headspaced nor shot since 1945.
Both rifles performed flawslessly. The carbine patterned 5 inches high at 50 yards probably a 3-4 inch group. The Enfield patterned 6 inches high at 100 yards. I ain't talking about the grouping, I am, however, looking for a new aperture sight.
A simple way to explain 7.62 headspace?
I asked this question a few weeks ago and got this great reply from Alan de Enfield about 303 headspace, it gave me a good clear mental picture of it all.
Now I'm asking the same question about 7.62 and my 1066 ishapore. This rifle seems very tight on the headspace, with the bolt requiring some force to close the handle. (Don't worry, it hasn't been fired like that. All else seems OK, so I suspect too tight headspace. ). With a cartridge chambered, what should the gap be between the cartridge and the bolt face?
And B) who stocks a no go gauge for 7.62? I've been looking but apparently in the wrong places.
And C)...is tighter better, as in zero gap? What would the penalty be?
thanks in advance...R:rolleyes:
From the previous post;
Quote:
Originally Posted by RJW NZ View Post
Hi all, I have a question, if there's a round chambered what is the ideal or allowable gap between the cartridge and the bolt head face? Just looking for a a simple way to explain all this stuff.
Quoted headspace of 0.064" - 0.074" is without the cartridge, 303 cartridge rim thicknesses vary but are normally around the 0.059" - 0.060" so the 'gap' (as in your question) can be 0.003" - 0.014"
Tighter is better (as they say)
From an old JOuster post by Peter Laidler
Anyone for 7.62mm CHS?
Posted By: Peter Laidler
Date: Tues 6 May 2008 11:36 am
Now for the biggie, the 7.62’s. The basic principle of headspacing hasn’t changed here but the practicalities have. Whereas before, on our rimmed .303” rifles we measured the GO NO-GO distance between the front face of the bolt and the rear face of the barrel, it’s all changed for the rimless 7.62mm NATO caliber rifles. Now we have to measure from the front face of the bolt to the cartridge seating at the neck. Well, that’s all pretty clear then ….., except that the neck is tapered so where EXACTLY on that neck do you take your GO, 1.628” and NO-GO 1.635 measurement from? Even if I told you it’d make no difference whatsoever because without the specialist measuring and more importantly, the calibration equipment, you’d still be none the wiser. The trouble with this is that you’ve got to take the word of the manufacturer of the gauge. And exactly where does HE take HIS measurement from but more importantly, WHO does he get them from. geting difficult isn't it?
Let me give you an example. My GO gauge gives you a close/GO reading of 1.628 but Bloggs & Co gauge may give you a GO reading of 1.575” for the same 7.62mm caliber. How can there be a difference of .053” between the two when they are identical? Well, it’s simple really. Our STANAG gauges are measured from one diameter around the neck while Bloggs & Co are taken from a different but larger diameter .053” further to the rear! That is really all I want to say about that.
The next obvious question for all you enthusiasts is where can I get a set of these gauges and the true answer is that I don’t know! But here’s what I propose. If you HAVE a set of spurious/said to be/reported to be/hope they are 7.62mm headspace gauges, I will calibrate them for you and tell you EXACTLY what it is you have. The fact remains that there are MANY gauges for all manner of 7.62mm rifles and machine guns ranging from the little bolt action L8’s right through to the L- whatever it is ferocious mini gun. And there are equally MANY for different lines of repair and functions, ranging from 1.622” to 1.648”.
Once I return them, calibrated, at least YOU know that if the ‘unknown’ gauge you sent to me to be calibrated comes back as a STANAG calibrated 1.6325 gauge (GO for the L1A1 rifle incidental.....) then it will suffice as a NO GO gauge with your 7.62mm Enfield provided that you slide a sliver of .003” steel shim across the bolt face first, on the basis that 1.632 plus .003 equals 1.635.
On the other hand, if you’re clever, you COULD just have the rear face ground down by .0045” to end up with a 1.628” GO gauge.
That just about covers the 7.62mm versions. The question of calibrating your gauges is one that needs to be looked into by ‘some friends’ on both sides of the pond. I can see already that this is about to open up a whole new can of worms...... But just hang on in there....................
Head clearance is what matters
Dear All,
I have followed all these threads on the ever-exciting topic of headspace, and wonder why so much energy is devoted to the matter. As has recently been noted:
1) If you are a collector who does not shoot, the subject is academic.
2) If you shoot, but do not reload, the subject is academic as long as the headspace is not so extreme that cases separate on the first (and only) firing, which could really spoil your day out at a competition.
3) For target shooters who do reload, all the information presented up to now can be boiled down to the following, for practical purposes:
The headspace for a rimmed cartridge is the space between the bolt face and the face of the recess in the chamber that takes the rim. The stretch of the cartridge case is basically determined by the DIFFERENCE between the headspace and the thickness of the rim itself - something which I would call the head clearance between the rim and the (head)space into which it has to fit. In other words, the end play of the cartridge in the chamber. The matter is complicated by the dynamic effects of bolt/chamber compression and expansion, but the first step is to have that clearance as small as can be without it actually becoming negative (which would mean you couldn't close the bolt on the cartridge. So if the rim thickness varies from one manufacturer to another, then an obvious move is to use those cases which have the thicker rims.
The next step,followed by all Enfield shooters of my acquaintance her in Mauserland, is never to full-size rimmed cartridges, but only use neck sizing. Of course, the die must be set up (as also noted in recent postings ) to allow for the spring-back in the press, otherwise the result can be a case with the neck too far forwards that has to be cammed into the chamber, and can be very stiff to extract. Neck-sizing means, in effect, sizing the case as for a rimless cartridge, so that rim thickness and the head clearance are no longer the determining factors. This treatment reduces the end-play of the cartridge in the chamber to pretty much zero.
Dear Friends Across the Pond. You may not be aware that SAAMI was only set up in 1926, and many of our old service rifles were made long before. And although I pointed it out a year or so ago on the old board, only now are a few people in this forum reluctantly coming round to the idea that the British Empire utterly failed to make rifles to SAAMI standards. How very short-sighted! And failed to make a system suitable for endless reloading of cartridge cases. How wasteful!
Turning off the sarcasm button and moving sideways a moment, consider the renowned M96 Carl Gustav (a.k.a. Swedish Mauser) rifles. Just about all made before SAAMI or even CIP. They swallow SAAMI no-go gauges without any problem. And cases fired in my Carl Gustav cannot be chambered at all in my Schultz & Larsen M69 match rifle (CIP standards). But head separation is not a subject for discussion - just use neck-sizing.
Or take a look at the bolt on the Swiss G96, 96/11 or K11, with lugs at the back. Then try and find "head separation" on the forums that cover Swiss rifles. No luck.
Synthesizing what has been put forward on this forum, a general recipe for milsurp and their brass is
1) First fire-forming with a slightly greasy case to get the maximum forming effect. I.e. merely wipe lube off case after sizing, but do not degrease it.
2) For all subsequent reloads, use neck-sizing with a properly adjusted press.
3) Except for that first fire-forming, keep all loaded cases dry to avoid continual and unecessary stress on the bolt lugs.
4) Forget SAAMI gauges, except for US-made rifles and ammo.
As usual, feel free to disagree, even heartily, but politely!
Patrick
safety aspects of 'lubrication'....
Yes remembering the 303 days in Australian rifle clubs I can recall hearing of instances where rifles were 'damaged' after firing wet ammunition but never saw such a rifle.
Of course in those far off days (Pre 1969) handloading was not permitted so rifle blow ups cant be laid at that door.....
As to the change in point of impact I can speak from actual experience. I always take pains to keep ammo for my 7.62 No.4s dry and free from oil/case lube.
One day at an early morning match there had been a heavy dew making the grass firing mounds really wet. We had a 'walk down' practice where you fire from 300 then 'walk' down to positions at 200 and then 100. Anyway I had my ammo clips in a plastic carry tray but dropped one clip onto the wet grass during a 'quick' reload.
I did my best to wipe it dry in the short time allowed but the rounds were still wet when they were loaded and fired.....sure enough my 200 yard target showed a very vertical spread with the (apparently) wet clip of 5 printing about 10 minutes high...(20 odd inches...)
Lost me that match. A lesson I never forgot. Perhaps the 7.62 No.4 is more prone to that than the 303..who knows. As for deliberately lubricating them...sure sounds crazy to me.
