What is Headspacing and help with Savage Mark II

[G P]

Hey guys, kinda new to gunsmithing.

I have a savage mark II from the mid 90's. Sometimes when I fire it the firing pin puts a small hole or cracks the casing and sends black powder back around the bolt and in my face. At first I thought this was because the firing pin was too sharp or long, so I filed it down very slightly. But the problem still occurs from time to time.

In addition, sometimes the extractors do not grab the empty casing. The casing is not jammed, it can easily be pulled out with a screwdriver or pocket knife, but the ejectors just aren't grabbing it.

I mentioned this to the guys at the local gun shop and they said it might be a head spacing problem. From what I gather, that means the distance between the flat face of the barrel and the bolt face. Is that the correct definition of headspacing? And could headspacing be the source of these problems?

 

[brnolvr]

I have seen old ammunition blow out at the rim due to the brass getting brittle over time, this is one possible cause if you ammo is new it could be like you mentioned a overly sharp or long firing pin.

As for the extraction failure, remove the extractor claws and clean the crud that build up underneath them, this allows the claws to fully grip the rim.

For headspace you'll need a set to check. Excessive headspace could cause your problem.
Headspace is checked between barrel chamber face and bolt face.

my Forster gauges measures as follows:

.043 Go
.046 NoGo
.050 Field

Hope this helps

 

[jethunter]

What is headspace?

Headspace is a measurement used to determine if the cartridge fits properly in the chamber. The chamber does need to be slightly larger than the cartridge to allow the cartridge to enter, but it must be a close fit within specific tolerances.

In the case of excessive headspace, the chamber is oversize (or in some cases it may be possible that the cartridge case is undersize). When a cartridge is fired in this oversize chamber, the cartridge case may rupture because the chamber walls do not support it properly under pressure. The ruptured case allows gases to escape through the action which can damage the rifle or injure the shooter.

Headspace is measured with a set of gages. The gages are shaped approximately like cartridges and are specific to each cartridge; ie, for a 30-06 rifle, a set of 30-06 gages must be used to measure headspace. Two gages are used, a "GO" gage and a "NO GO" gage.

The "GO" gage SHOULD allow the bolt to close when it is inserted into the chamber. If the bolt will not close on a "GO" gage, it means that the chamber is under size and the rifle should not be fired. Undersize chambers are usually not encountered by the shooting public unless the chamber was not made properly by the builder.

The bolt SHOULD NOT close on the "NO GO" gage when it is inserted into the chamber. If the bolt does close on a "NO GO" gage, it means that the condition of excessive headspace is present, and the rifle should not be fired until it can be corrected by a gunsmith.

 

[Phadeout]

What is headspace?

Headspace is a measurement used to determine if the cartridge fits properly in the chamber. The chamber does need to be slightly larger than the cartridge to allow the cartridge to enter, but it must be a close fit within specific tolerances.

In the case of excessive headspace, the chamber is oversize (or in some cases it may be possible that the cartridge case is undersize). When a cartridge is fired in this oversize chamber, the cartridge case may rupture because the chamber walls do not support it properly under pressure. The ruptured case allows gases to escape through the action which can damage the rifle or injure the shooter.

Headspace is measured with a set of gages. The gages are shaped approximately like cartridges and are specific to each cartridge; ie, for a 30-06 rifle, a set of 30-06 gages must be used to measure headspace. Two gages are used, a "GO" gage and a "NO GO" gage.

The "GO" gage SHOULD allow the bolt to close when it is inserted into the chamber. If the bolt will not close on a "GO" gage, it means that the chamber is under size and the rifle should not be fired. Undersize chambers are usually not encountered by the shooting public unless the chamber was not made properly by the builder.

The bolt SHOULD NOT close on the "NO GO" gage when it is inserted into the chamber. If the bolt does close on a "NO GO" gage, it means that the condition of excessive headspace is present, and the rifle should not be fired until it can be corrected by a gunsmith.

That was excellent...

But what does the Field gauge do?

 

[jethunter]

That was excellent...

But what does the Field gauge do?

You don't need to use a "FIELD" gage if you have measured with the "GO" and "NO GO" gages.

My understanding is that the field gage was developed by the military to check battle rifles that failed the NO GO test. Under wartime conditions slightly larger tolerances could be accepted, because there was a shortage of replacement rifles and any rifle is better than no rifle when someone is shooting at you.

 

[Baribal]

Actually, the Field gauge is the upper limit from where your rifle starts to be dangerous. Over that point many firearms won't even light a primer and if ever it lights it, the brass will be prone to crack and the primer will set back, too.
The headspace is a different measure depending on how the cartridge was designed.
The rimmed cartridges headspaces with the rim thickness.
The rimless cartridges heaspaces on the shoulder and is measured by the diameter mid-way on the shoulder angle
The Belted magnums headspaces between the base and the top of the belt, but some may also headspace at the shoulder.
The straight walled pistol/revolver rimless cartridges, with some exceptions, headspace at the mouth (the "neck") of the case. For these, the case lenght, after trimming, becomes a critical dimension.

If a rimfire cartridge fails on the rim, you must have a firing pin protusion problem, not related to headspace. also check the rim at the chamber level to determine if there is no damge done to the flange by repeatedly dry firing the rifle.
Rimfire rifles are not really prone to headspace problems, unless the bolt was replaced by a non-matching one.

 

[jethunter]

Actually, the Field gauge is the upper limit from where your rifle starts to be dangerous. Over that point many firearms won't even light a primer and if ever it lights it, the brass will be prone to crack and the primer will set back, too.

Agreed, but I would add that for most of us a chamber that fails the "NO GO" test needs the attention of a gunsmith. The NO GO gauge has some built in safety margin, the FIELD gauge does not.

 

[Quaid]

If a rimfire cartridge fails on the rim, you must have a firing pin protusion problem, not related to headspace. also check the rim at the chamber level to determine if there is no damge done to the flange by repeatedly dry firing the rifle.
Rimfire rifles are not really prone to headspace problems, unless the bolt was replaced by a non-matching one.

This was the first thing that came to my mind when I read the description of the symptoms, not a headspace problem.

If it turns out that the firing pin protrudes too far, that is an easy fix. Just grind a tiny bit off, polish, and test. Repeat if necessary.

 

[sunray]

Headspace is a rifle manufacturing tolerance that allows the use of any manufacturer's ammo in any rifle of like chambering. It's from the bolt face to a spot in the chamber. Keeping with the .30-06, the spot is on the area of the chamber where the case shoulder fits. A rimmed case headspaces on the rim. A belted case on the belt. Rimless pistol cases and straight walled rifle cases headspace on the case mouth.
The 'Go' guage(Headspace guages measure nothing. They only tell you if the headspace is within tolerance.) tells you if the tolerance is within minimum spec.
The 'No-Go' tells you low end maximum tolerance. The 'Field' is absolute max.
The bolt should close completely on a 'Go'. It should not close on a 'No-Go' but if it does, try the 'Field'. If it closes on the 'Field', the headspace is excessive and th erifle is not safe to shoot with any ammo.
In the case of your .22, it's most likely the ammo. Possibly headspace, but not likely. Start by changing ammo, then remove and cleaning the bolt, inside and out. That may fix the extraction issue as well, but look at the extractor and spring. Go here for a .pdf manual.
http://www.savagearms.com/downloads.htm

 

[Quaid]

I might recommend this quick read:
h ttp://www.rimfirecentral.com/forums/showthread.php?t=243342

The gentleman that wrote that has done quite a lot of work with the Savage Mk II's and knows his way around them. If you're still unsure about the problem and or solution, I'd get in touch with him.

 

[G P]

Update:

After a light filing on the firing pin and switching to Federal ammuntion from remington thunderbolt I have not had any pierced casings.

The reason the gun was not pulling the empties form the chamber was because the ejector spring clip had become stretched and was not pushing the extractors close enough together to grasp the rim of the casing. I basically bent it back to shape with some pliers and now the gun works perfectly. I still need to test fire a few more rounds but so far so good.

 

[Quaid]

Glad you got it sorted out.

 

[Ganderite]

As I read the first posting, it reminded me of a batch of 22 ammo I had with bad brass and it sometimes blew.

If the pistol does this with different makes of ammo, it is not the brass, but brass is my best bet.

Clean the bolt and extractor with solvent and a toothbrush. They do tend to crud up.

By the way - there are two ways to have excess headspace. Chamber too deep or bolt face too far from back of case. First is not a danger, second is very dangerous.

Chamber too deep. Load a 308 case in a 3006. About a half inch of excess headspace - but no danger. If case fires it just comes out looking like a 444 Marlin Rimless.

Bolt too far from rear of case. This allows the solid section of the case (the web) to be unsupported by chamber wall, and case will blow. This destoys the rifle.

In the latter situation, the headspace might be perfect, but the chamber cut too shallow. By threading barrel so barrel is moved forward a bit, the headspace can be perfect, but the rifle a disaaster. I have seen this.

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