Headspace problem on 30-30

[Milsurp Junkie]

I recently picked up a Mossberg 472 (actually the Montegomery Ward's version) Lever action 30-30 in a trade. The rifle looks very gently used: 98% blueing, no dings on the stock, strong rifling, good crown, etc. I was looking for a lever action (always wanted one) hunting rifle.

The gun is currently in pieces, as the guy replaced the sub frame (it was cracked), and could not get the rifle back together. Not a problem, as I have a bit of free time on my hands and Gun Digest has the disassembly instructions.

Here is the problem. The guy indicated that he was having a difficult time extracting the rounds. He also included 2 boxes of factory brass from his shooting session. I noticed when I got home that each and every fired round had primers blown out from their pockets.

Obviously, a headspace issue. Where to start? Should I even try? I talked to one gunsmith in town, and he indicated that it would be cheaper to just buy another one as the problem could be in the locking lugs, the receiver, or the barrel. Opinions?

Jonathan

[jnovotny]

Not necessarialy a head space problem, were the rounds fired of the home brew type? Could be overpressure in that case. Would look at shooting some of your own stuff. Then you will know what you are dealing with. Sticky cases, blown primers are clasic signs of over pressures. Put the thing together and shoot some of your reloads or factory ammo. Keep us up to date would be interesed in what is going on.

[docone31]

If you really want to be sure, I might contact Marlin Firearms and make arrangements to send it to them to rebuild.
There is something about the primers.
I had Marlin rebarrel an old 30-30, a 336, years ago.
Came back a good shooter.
I would be tempted to take that route. Didn't really take long either.

[Char-Gar]

YOu will get lots of advise and possible causes from your question. But you thread indicates..

1.. a cracked sub frame
2. Can't get it back together
3. Hard extraction
4. Blown primers on factory ammo.

My first guess is some idiot shot one or more serious overloads in that rifle and it is pretty well toast. Lots of luck, but I think it will come out your traded for a trot line weight.

There is a big moral to this story and I will let you figure out what it is.

[Trailblazer]

Two things:
1. A Mossberg 472 is not a Marlin so Marlin won't help you.
2. The primers in fired 30-30 cases often protrude from the case head because the chamber pressure isn't high enough to stretch the brass and push the case head against the bolt face and reseat the primer. How far were they blown from the pockets? The only way to check head space is to assemble it and test it with a head space gauge.

[BBA]

Is it possible the bolt is not fully closed?

[Milsurp Junkie]

It is possible that the cracked sub frame was allowing the bolt to travel a bit to the rear. I got everything reassembled, and it seems to lock up tight. While it was apart, I saw that nothing looked bent, peened, cratered, etc. All pieces seem to have normal wear and rub marks. I am tempted to go and sandbag it to a table, and fire a round through it (while pulling a string) to see if the primers are still up.
Oh, by the way, the primers were up approximately 2-3 post-it note thickenesses (I am sorry the battery in my caliper is dead).
Jonthan

[Multigunner]

Look for indentation of the bolt face around the firing pin hole.
I've seen many older rifles which had indentations there due to the primer striking hard against the breech face before the case head moves back.
Old Mercuric primers were very hot, sometimes giving very high pressures in the primer pocket. If case hardening of the breech face isn't thick enough the face can be deformed. Pitting around the circumference of the primer contact due to corrosive salts and gas leakage increases the likelyhood of indentation.
Some people also try to polish out such rings and end up thining the hardened surface as well as increasing headspace.

[John Taylor]

You can do a quick head space check without a head space gauge. Add layers of masking tape to the base of a factory loaded cartridge and keep checking the fit in the chamber till the leaver will not close all the way. Take one layer off and measure the rest with a micrometer. Or count the layers allowing about .004" for each one. Most lever guns are a little loose on head space, two layers of tape or about .008" is were most used lever guns will come in. I have had 94s come in the shop with .016" and they are still being used. With Winchesters the cure is a new locking lug from Wisner's, he has several oversize ones to take up head space. The most common practice to take up head space it to set the barrel back a turn or two and rechamber. But first make sure there isn't any other problems like a cracked frame or a bent lever.

[johnlaw484]

John, you are right on with that.

[bigdog454]

I have a 22-250 that has head space problem, I use only reloads in it and have set my dies so that when I resize they don't move the neck back. I now shoot a 22-250 wildcat so to speak. Solved the problem as long as I don't use factory ammo.
But: I understand that the 30-30 head spaces on the rim. New problem.

[Milsurp Junkie]

I reassembled it. Rounds cycle completely fine if I work the action w/ emphasis. I can not lightly close the lever, as the bolt will not completely close (looks like it is hanging on the extractor). I fired one round through it, it looks the same as the others (primer still sitting up out of the pocket). I will get batteries for my caliper to tell how much they are sitting high.

Jonathan

[Trailblazer]

I have some fired 30-30's here with primers sticking out about .009". This is in R-P brass and the rims measure .057" to .059" thick. According to Dunlap's Gunsmithing the "rim space" should be .063" to .067". I believe "rim space" is maximum rim thickness of .063" plus maximum headspace of .004". If you do the math you will see that my 30-30 is right at the maximum headspace with primers out .009". Seems like a lot but those are the facts.

[MtGun44]

How about casting the chamber. A short chamber would cause the same issues as too
long brass in a normal chamber, basically the neck couldn't let go of the bullet. This is
consistent with your difficulty chambering a round. Look for marking on the brass at
the very end of the neck as if the chamber is too short.

Blown primers is a SERIOUS pressure sign, NOT likely from minor excessive headspace.

Something is wrong dimensionally, probably in the chamber or bore. You are using
factory ammo, right?

Bill

[John Taylor]

MtGun44, he is not talking in blown primers as having a hole in the primer. The primers are backing out because of headspace. The 30-30 does not have enough pressure to stretch the brass back to the bolt face so the primer backs out to meet the bolt face. Firing pin pushes the cartridge forward, fires cartridge, cartridge expands with pressure gripping chamber wall, pressure pushes primer back. This is very common on lever guns.

[Multigunner]

I have a few Federal .30-30 fired cases I found at the range.
These show obvious signs that the case haed made full contact with the breechface under pressure, but the primers stand proud by several thousandths.

Breech bolt or lug springing was noted from the first cartridge breech loaders, and some designs depended on it to loosen the fired case for extraction.

I have a strong feeling that in some instances at least, the case if strong and springy will in part return to very close to its unfired dimensions, and residual pressures inside the primer pocket hold the primer against the face while this goes on. The case then springing back into the chamber leaving the primer protuding slightly.

Its fairly common for cases used only with very light loads to return almost to the unfired dimensions, or in the case of rimless cases sometimes shorten as far as headspace goes.

When using very light rat loads in my S&W .38 Sp I found that I had to drill out the flash hole oversized, other wise the primer would stay firmly locked against the recoil shield tying up the cylinder. There was not enough gas pressure from these tiny charges to overcome residual pressure in the primer pocket to reseat the fired primer flush with the case. The case of course has to spring back to shape otherwise extraction (especially six hulls from six chambers at one time by the tiny revolver ejector rod) would be extremely difficult.

[John Taylor]

I thought I would throw out another type of repair for head space although it is usually done for a faulty chamber. The chamber can be sleeved and left a bit long. Have done this many times but only on rifles that still have a good bore. If the bore is not good then it's time to install a liner which will work to take up head space problems at the same time.

[Milsurp Junkie]

After miking the primers (actually had to mike a piece of cardstock that seemed to feel even with the primer height), it seems that the primers are up maybe 0.002 to 0.003". Most of the rims that I measured on the Winchester factory brass was 0.057" thick.
Jonathan

[Multigunner]

After miking the primers (actually had to mike a piece of cardstock that seemed to feel even with the primer height), it seems that the primers are up maybe 0.002 to 0.003". Most of the rims that I measured on the Winchester factory brass was 0.057" thick.
Jonathan

I would not give that little protrusion a second thought.

The smaller diameter .30-30 case can take a great deal more pressure before reaching its limit of elastic deformation (vs Plastic deformation). In other words a chamber pressure level that permanently stretches the case of say a .303 ( a case of similar shape but larger diameter and with more bearing of case wall to chamber wall) won't be as likely to give plastic deformation of the smaller case.

I recently ran across a disscussion on the 94 Big bore Winchesters and problems some had with the larger diameter cases compared to the .30-30 in the same basic action type. I can't recall all that was said but I think I got that much right.

PS
An online study of the effects of chamber finish on case deformation put the pressure applied by the average Large Rifle primer at about 900 PSI (IIRC).
But the primer pocket is also subject to the full chamber pressure during bullet travel, and then must bleed this pressure back out through the flashole while residual pressures are still in case and bore.
Its a balancing act of many forces at work at one time, governed by finite time limits for each phase that are almost too small to measure.

With the poor (if indeed any) primary extraction of lever action rifles, a cartridge that left a case tightly expanded in the chamber would be difficult to operate in a hurry.

[MtGun44]

OK, sorry I misunderstood "blown out from their pockets" as blown primers, not
protruding primers. Sorry for the confusion.

I have these only when I am shooting very light loads.

Bill