All this headspace information

[Patrick Chadwick]

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

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Parashooter]

. . . 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.
. . .
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.
. . .
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.
. . .
Patrick

Patrick, it seems you've come a long way toward appreciating some parts of the issue but still have areas of misunderstanding.

Press "spring-back" is negligible in neck sizing, simply because sizing just the neck takes very little force. Press flex is an issue when full-length sizing, especially with thick, heavy cases. The primary source of neck-sizing problems is attempting to do it with FL dies that contact the body before the neck is sized far enough. This contact often compresses the body and displaces the shoulder forward.


Smoked cases reveal body contact when attempting to neck-size with full-length sizer dies.

Head separations certainly occur with the Swiss 7.5 rifles and have been discussed at length on the forums dedicated to these arms. Here's an image from one such thread -



While fire-forming with lubed cases is an effective technique for some handloaders, others object to the practice on the grounds that it delivers unnecessary stress to the bolt and receiver. Fire-forming with some kind of spacer ahead of the rim is nearly as effective in reducing initial stretch and avoids the controversy. A spacer that also serves to center the case is additionally useful, especially with fat chambers or skinny brass.

Effective neck sizing often requires special dies, dimensioned to clear body and shoulder. It is the die position that is adjusted to give the amount of sizing desired, not the press. Most common reloading presses aren't readily adjustable in any way that affects neck sizing.

Whether or not increased stress on the rifle resulting from regular use of lubed cases is more important than reduced stress on the cases is arguable and will vary with the relative value and strength of the rifle and of the cases.

It seems pointless for a recreational handloader to obsess about gauges or varied specifications when the truly critical factor, the actual fit of his handloaded ammo in his individual rifle(s), can be determined and managed using no other gauge than the rifle itself and his "calibrated" fingers. Leave headspace gauges to gunsmiths fitting barrels or bolts, armorers or buyers checking numerous used rifles, or commercial reloaders producing ammo to be used in a variety of arms - and life gets much simpler.