Lever Action headspace

[newton]

I was just sitting here thinking about my 30-30 and a question came to mind. I tried googling the answer, but cannot find it(probably not wording it just right).

What causes a lever action(rimmed cartridge) to see an increase in headspace?

I know that wear and tear will eventually show itself, but is that it? I guess I am curious if it would come from shooting or if it would come from wear by racking the lever up and down.

Just a curiosity question really. Wondering if there is a science behind it.

[MBTcustom]

Excess headspace would be a very bad thing in a lever action rifle. If you find that condition present, the most likely cause would be the rifle having been made like that which is very unlikely.
If excess headspace were to "develop" as it was used, it would be a function of the reciever stretching, the bolt compressing, the locking block becoming sheared, or a combination of all three, or the barrel stripping the threads.
The reason why this is almost an impossibility is because of the weak design of these rifles. If anything gives, it will be the thin barrel rather than the points I mentioned above. I have had a Marlin 1895 in the shop that was literally cut in half by a double charge, and the boltface and recoil lug areas were virtually unharmed in any way even though the cartridge had burst the barrel and receiver so it looked like a banana that had firecracker exploded inside.
I suppose anything is possible given the number of rifles of this style produced, but I've never seen headspace increase in any lever action or modern bolt action.
WWII rifles are a different story entirely, but that's not surprising considering the desperate conditions European, and eastern firearms were being produced under. A soft receiver will give way over time, but that is simply a manufacturing defect.

[Hick]

Goodsteel said it all. I've got two Winchester 94's, one from 1949 the other from 1968. You've got to try real hard or cycle the action a whole lot with inadequate lubrication to wear things down before you can have a headspace problem. I've never heard of it happening with normal use.

[pietro]

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FWIW, the Achilles Heel for leverguns is right under the chamber, where the barrels are thinner to allow the magazine tube to pass into the magazine throat bored into the action face, and still remain parallel to the bore C/L.

The larger the bore, the larger the magazine tube - and the greater the thinness.


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[MBTcustom]

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FWIW, the Achilles Heel for leverguns is right under the chamber, where the barrels are thinner to allow the magazine tube to pass into the magazine throat bored into the action face, and still remain parallel to the bore C/L.

The larger the bore, the larger the magazine tube - and the greater the thinness.


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You do realize that the thread tenon is MUCH thinner than that little groove you are referring to, and the action does nothing to help it contain pressure. A pressure containing vessel is only as strong as it's weakest point, and the entire barrel itself isn't very big on lever action rifles especially right over the chamber area. If you look at the amount of metal surrounding the chamber, leverguns fall in the same area as revolvers and pistols. You don't even have 1/8" of steel surrounding the chamber.
Check out this Marlin 1895 barrel that was burst by a double charge of 2400. True, it opened more at the bottom of the barrel than at the top, but you'll notice the barrel threads are gone.
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Now the action was blown open, but the lug and bolt were still in good shape.
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Point is, the weak point of these rifles is right where the barrel joins the receiver because both the barrel and the receiver sacrifice strength so that they can be joined together.

Now, I think popper has a good point about closing the action on hard to chamber loads (like somebody who is trying to engrave the bullet when closing the action) but first of all, you would have to do this a whole lot for it to amount to any appreciable wear on the lug or it's tracks, secondly there are not many people who would make a habit of shooting thousands of rounds of improperly fitting ammo for a rifle, and thirdly if they did it was because they were enjoying excellent accuracy from hand loads, in which case headspace is much less of an issue because they will be mindful of how much they are sizing their ammunition.

[missionary5155]

Good morning Tim
Thank you for those photos ! That does help see the weakest area of the Marlin action. What with those cuts for ejection and loading it is amazing how modern steel will support pressure impulses.
Mike in Peru

[MBTcustom]

Those weaknesses were designed into the receiver for your protection. If the barrel bursts, the receiver is designed to allow the path of least resistance to carry the blast and shrapnel to the right, away from the shooter. Also, many people complain about Marlin's extra thick forends that look "clunky" in comparison to the Winchester's etc etc. That also helps protect the shooter when the rifle goes kaboom. Had the owner of this rifle had his left hand on the wood forend instead of wrapped around the receiver, he would have walked away without a scratch as the splintering forend would have protected him in spite of the fact that the rifle was literally cut in half by a double charge while he was holding it.
Notice how thick the LH panel is and how weak the RH panel is. Uninformed people complain about how you can often see the barrel threads cutting into the magazine tube hole on these rifles, and they think it's a defect. That weakness, coupled with the threaded hole just blow it, makes the front of a Marlin act like a perforated rip line on a sheet of paper. If the barrel ever gives way, the RH panel tears away instantly carrying the hot gasses and schrapnel away from a right handed shooter and creates a bit of a blast shield/shock absorber.
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Many firearms are designed in this way. Glocks are awesome about this. I've seen a couple Glock's whos owners double charged. The pistols went to pieces, but the RH grip panel tor away from the pistol and protected the shooter's fingers while the catastrophe was happening. They had a numb hand, but not a single cut. These designs are ingenious. There's a lot more to a rifle than just making it go bang and not have any sharp edges.

[bob208]

we found years ago the lugs would wear causing headspace. the cure was to get the front face of the lugs built up with hard chrome.

[pjames32]

Goodsteel-you are not making this left handed shooter feel comfortable!
PJ

[John Taylor]

I see many lever guns come in with excessive head space. Had a 94 that had .025" head space and the customer was still shooting it with no problems. Most lever guns will close on a no-go gauge. If they are set up with zero head space they become difficult to open after firing. Not sure what causes head space because I see no signs of ware in most. If the frame was stretching the action would start to bind. So far the only frame that I have seen that stretch far enough to cause problems was an Italian brass frame Henry in 45 colt.

[Gtek]

In my experience having rims that do not meet SAAMI spec in thickness does not help the situation.

[44man]

With a 30-30 you can head space off the shoulder just like a bolt gun by sizing right.

[gnoahhh]

In the case of Savage lever guns, when they were being built the guys would simply screw in a new barrel into the receiver fully chambered and with the extractor notches lined up. Then various bolts were tried until one fit within the headspace parameters, the bolts having been made in varying lengths. (Note that the Savage bolt has no locking lugs, it butts solidly against the back of the receiver.) When building my latest M1899 custom takedown I played a frustrating game of mix-and-match until I finally found a bolt long enough to correct the impossibly excessive headspace I initially encountered.