How can a case expand enough to stick in the bore??

chaz12 · November 6, 2009, 09:06 PM

after the cartridge is fired??

I have been looking for the cause of intermittent jamming during extraction on a Marlin 336 in .30-30. I took it to a gunsmith; I have polished parts in the action; I have taken it apart and put it back together many times; I have worked the action with parts out trying to see the cause of the jamming. Nothing has made any difference. I am back to square one.

It seems to me that, once in while, after a shot, a casing is simply jammed so tight it the bore that the bolt will not open. I can cycle a live round thru the rifle indefinitely with no problem. The cartridge feeds into the bore and ejects out perfectly. But I am sitting here this evening with a spent casing and feeding it into the bore. As soon as I close the lever, I can feel that it is jamming tightly into the bore. It is very difficult to extract; very nearly the same level of jamming I experience at times after firing a live round.

I know the casing expands as it fired. But can it expand so far that it jams itself in the bore? If so, why? By the way, I only use factory ammunition. This in particular happens to be PRVI, but the same jamming has occurred with Winchester and Remington.

Obviously, the next step is to send the rifle back to Marlin, but I would like to know what might be causing this anyway.

Thanks

Chaz

Christchild · November 6, 2009, 09:38 PM

The 1st thing that comes to my mind... Case Neck Length.

Factory ammunition (from my experiences with factory brass) can often have Case Neck Length's longer than SAAMI Maximium, and if the dimensions of the portion of Your chamber that conform to/house the case neck, are fairly tight (in length), the case necks could possibly be portruding into the throat, causing the case to get stuck, as the fired brass will be slightly larger after it expands upon firing.

If You have, or have access to a set of Dial Calipers, check the length of Your fired cases. 30-30 Winchester has a Maximum case length of 2.039". Much longer than that, combined with a "tight" chamber dimension, could possibly result in the problem You're having.

Just my $0.02.

eric75 · November 6, 2009, 09:58 PM

I have a rifle that came from the factory with a ring in the chamber because the chambering reamer had a chip in one of the flutes.

Inspect your fired brass closely for any markings that were not there before firing.

Clean the chamber but do not attempt to polish, lap or hone the chamber. Even if the headspace is re-checked and OK'd afterward, it will do bad things to your brass.

If you send it back to the factory, insist that they re-cut the chamber to an adequate depth to completely remove all the old surfaces. It is enough machine work to do it properly that they will probably go the cheaper route and replace the whole barrel.

Edit: after reading your post again, I think Christchild is more correct that myself about the actual cause of your problem. Do inspect the spent brass.

U.S.SFC_RET · November 7, 2009, 05:39 AM

Inspect that chamber for rusted pits. If there are pits then the brass will swell into those pits and sieze.
Frequently happens to some of the semi auto types that I know of. Remington comes to mind.

MTT TL · November 7, 2009, 07:47 AM

Quote:

If there are pits then the brass will swell into those pits and seize.

Assuming the ammo is good, I second that, could also be some other kind of damage in the chamber, not just rust. I saw a 9mm chamber that had become badly scratched due to improper cleaning methods that was a jamomatic.

bamaranger · November 8, 2009, 01:13 AM

Pitted chamber, maybe. What about a weak extractor, slipping off the rim just when it needs to pull a bit more. I's try that before I started to rechamber/rebbl.

November 6, 2009, 09:06 PM	#1
chaz12 Member Join Date: May 22, 2008 Posts: 95	How can a case expand enough to stick in the bore?? after the cartridge is fired?? I have been looking for the cause of intermittent jamming during extraction on a Marlin 336 in .30-30. I took it to a gunsmith; I have polished parts in the action; I have taken it apart and put it back together many times; I have worked the action with parts out trying to see the cause of the jamming. Nothing has made any difference. I am back to square one. It seems to me that, once in while, after a shot, a casing is simply jammed so tight it the bore that the bolt will not open. I can cycle a live round thru the rifle indefinitely with no problem. The cartridge feeds into the bore and ejects out perfectly. But I am sitting here this evening with a spent casing and feeding it into the bore. As soon as I close the lever, I can feel that it is jamming tightly into the bore. It is very difficult to extract; very nearly the same level of jamming I experience at times after firing a live round. I know the casing expands as it fired. But can it expand so far that it jams itself in the bore? If so, why? By the way, I only use factory ammunition. This in particular happens to be PRVI, but the same jamming has occurred with Winchester and Remington. Obviously, the next step is to send the rifle back to Marlin, but I would like to know what might be causing this anyway. Thanks Chaz

November 6, 2009, 09:38 PM	#2
Christchild Senior Member Join Date: June 19, 2009 Location: Loadbenchville, Bolt 02770 Posts: 339	The 1st thing that comes to my mind... Case Neck Length. Factory ammunition (from my experiences with factory brass) can often have Case Neck Length's longer than SAAMI Maximium, and if the dimensions of the portion of Your chamber that conform to/house the case neck, are fairly tight (in length), the case necks could possibly be portruding into the throat, causing the case to get stuck, as the fired brass will be slightly larger after it expands upon firing. If You have, or have access to a set of Dial Calipers, check the length of Your fired cases. 30-30 Winchester has a Maximum case length of 2.039". Much longer than that, combined with a "tight" chamber dimension, could possibly result in the problem You're having. Just my $0.02. __________________ If the Ignorant say to You, "The Soul dies like the Body", reply to them, "The Flower dies but the Seeds remain"... That is a Law of God.

November 6, 2009, 09:58 PM	#3
eric75 Member Join Date: October 22, 2006 Posts: 18	I have a rifle that came from the factory with a ring in the chamber because the chambering reamer had a chip in one of the flutes. Inspect your fired brass closely for any markings that were not there before firing. Clean the chamber but do not attempt to polish, lap or hone the chamber. Even if the headspace is re-checked and OK'd afterward, it will do bad things to your brass. If you send it back to the factory, insist that they re-cut the chamber to an adequate depth to completely remove all the old surfaces. It is enough machine work to do it properly that they will probably go the cheaper route and replace the whole barrel. Edit: after reading your post again, I think Christchild is more correct that myself about the actual cause of your problem. Do inspect the spent brass. Last edited by eric75; November 6, 2009 at 10:02 PM. Reason: re-read original post

November 7, 2009, 05:39 AM	#4
U.S.SFC_RET Senior Member Join Date: December 12, 2005 Location: The Old line State Posts: 257	Inspect that chamber for rusted pits. If there are pits then the brass will swell into those pits and sieze. Frequently happens to some of the semi auto types that I know of. Remington comes to mind. __________________ 1. Treat every firearm as if it were loaded. 2. Never point a firearm at anything you do not intend to shoot. 3. Keep the finger off the trigger and firearm on safe until ready to shoot. 4. Know the target and what's beyond it.

November 8, 2009, 01:13 AM	#6
bamaranger Senior Member Join Date: October 9, 2009 Location: North Alabama Posts: 187	what about this Pitted chamber, maybe. What about a weak extractor, slipping off the rim just when it needs to pull a bit more. I's try that before I started to rechamber/rebbl.