What to do about headspace after #4 bolthead?

[Edward Horton]

So my 30-30 with its rear locking lugs never flexes.

The same for the 30-40 Krag rear locking lug never letting the action flex.

And the Remington 788 with its rear locking lugs must never flex even with the higher pressure.

Or is it just British rifles with rear locking lugs that flex.

I’m glad our “Superior American” rifles don’t flex when fired




(Did I tell you I like my Enfield’s Jim K)

[Son]

I'm reading Jim's post above and looking at the many pics of sectioned cases in this thread and thinking the headspace would have to be near .250" (a quarter of an inch) to allow the thick part of the base to be out of the chamber on firing.

[Parashooter]

I'm reading Jim's post above and looking at the many pics of sectioned cases in this thread and thinking the headspace would have to be near .250" (a quarter of an inch) to allow the thick part of the base to be out of the chamber on firing.

.250" would be kind of on the high side. If you notice the yellow lines in the image below, they're marked with distances from the rear surface of the case.



The thickest web here is only a tad more than .180", while the thinner ones are about .155". Still, a .303 rifle would have to be in very sad shape to have that much headspace.

It's always seemed to me that some folks on these forums enjoy emphasizing the dangers of excess headspace. I'm more inclined to believe General Hatcher:

". . . With good strong actions and moderate pressure loads, and especially if the shooting glasses are worn, this trouble is not particularly dangerous, but is annoying and inconvenient. Very little, if any, gas escapes to the rear, because the back end of the cartridge, which remains in the chamber, acts as a seal. In fact, it is just such short brass cups that the Germans have for years used as the breech seals in their heavy artillery . . .

". . . In my own experimental firing I encountered at least a couple of hundred such separations, and every one of my several thousand students had to experience and correct this situation several times and I never saw enough gas escape to hurt any one. . . "

"Our riflemen are used to measuring the headspace of their rifles by thousandths, and are prone to become very much alarmed if the headspace gauges two or three thousandths of an inch more than the normal maximum. This is a good safe attitude to take, but it is something like measuring cordwood with a micrometer. . ."

In a lifetime of shooting and handloading, I've had about a hundred case head separations (mostly from excess full-length sizing and refusing to discard worn-out brass). Like Hatcher, I've never felt even a trace of gas when this happens. And because I keep a "broken shell extractor" handy, it's never been more than a momentary inconvenience.

[Bindi2]

Head separation is more to do with poor quality brass, wrong measurement used in manufacture or resizing than headspace. The problem seems to com from one souce only and that is not the home.
I use No1s, 4s and 5s and i have had more failures in the later actions because of the brass used.

[Edward Horton]

The measurements are meaningless if the cases are not manufactured from the same grade brass or brass of the same specifications, if someone can reload Greek HXP cases 30 times and a Winchester cases only lasts three firings someone is adding pot metal to the mix or American manufactures don’t know how to make .303 cases.

Tight headspace to me is making your American .303 cases last longer if you reload.

P.S. Bindi2, your two fingers must be faster than my two fingers but at least our fingers think alike.

[Son]

Parrashooter- I'm a subscriber to the same logic that you demostrate so well in your postings. I'm always trying to convince new owners that they don't need to "get a bigger bolthead in case their rifle is out of spec next week", but should be able to fire another 5000 rounds before even checking headspace again. The problem is, they don't seem to want to hear that.

Jim K seems to think there is a direct corrolation between excessive headspace and burst cases. The thought that a body can flex enough to allow the thin walls of the case to get outside the chamber, and then to say "in most cases the receiver springs back and leaves little sign of what happened except a blown case, a ruined magazine, and usually a departed extractor".....Hmmm, cannot concede to that possibility.

One other thing that doesn't often get a mention, but was demonstrated so well in your posting, Parrashooter, is the Lee Enfield's ability to safely vent gasses at the rear of the chamber with little or no discomfort for the shooter. Congrats in getting that message across too! It shows the action to be one of the safest around if a case rupture does occur.

Along with yourself, Ed and Bindi, I agree ruptured cases and head separations are a handloading issue, down to use (and abuse) of whatever raw materials you have on hand and their ability to endure said use.
The "quarter of an inch" bit was to try to demonstrate that by the time the case was far enough out to expose the thin sidewalls, the bolthead was clear of the receiver ring, and the handle couldn't turn down into it's locking recess without already having serious damage somewhere, but that had already been said too.

As a point of interest I measured the base thickness of several HXP89 cases. They were all around .191". I knew they would be thicker, the case capacity of these is noteably less than all others I have checked.

[Peter Laidler]

I agree with you there Son. In all of my time as an Armourer, I only knew of two breech explosions with No4 rifles and I mentioned those on the Jouster Forum. And incidentally, they were nothing to do with CHS.

This thread started in relation to a No4 bolt head (or a No4 rifle....) and it was established many moons ago that of a rifle couldn't CHS on a No3 bolthead, thgen it was fit for scrap as the body was worn beyond the induction hardened locking surfaces.

Ed, I'm at a bit of a loose end tonight and tomorrow. Will you ask the girl on your header if she'd like a game of volley ball at my place tonight.

[louthepou]

Said very respectfully: it's Basketball, Peter.

Unless that volley ball was painted to mimic the basketball paint scheme.

[Jim K]

I am delighted to know that it is impossible for an SMLE to flex or bend. But just in case you wonder what would happen should the impossible occur, here is a picture of the cartridge case. I also have the wrecked magazine.

Jim

[Edward Horton]

Jim K

That case would have been ½ to ¾ of an inch outside the chamber when the sidewall of the case blew out which makes me think you had a delayed hangfire and the bolt was partially open. What is remarkable is you had an explosion at the rear of the case and an implosion at the front of the case.

In order for the action to flex and move that much the bolt and receiver would have been completely destroyed.

The only other possibility I can think of is the cartridge case was struck by anti-matter at the instant of firing almost pulling the cartridge case into an alternate dimension.