Author Topic: fixing a headspace problem  (Read 2360 times)

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enfieldshooter303

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fixing a headspace problem
« on: March 30, 2009, 12:55:35 AM »
what exactly does a gunsmith do to fix headspace issues on a bolt action rifle?

Rifleman1911

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Re: fixing a headspace problem
« Reply #1 on: March 30, 2009, 01:17:11 AM »
 Well  with the lee enfield they change the bolt head to increase or decrease the head spaceing on the rifle to make the head spaceing correct, As I was taught not to exchange the heads on the rifles when I was in the Canadian Rangers. Now how they do it on solid non-swiveling bolts I dont know.  Mabye get a longer bolt to extend the bolt some how to make the cartrage seat better.?

docbuckhead

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Re: fixing a headspace problem
« Reply #2 on: March 30, 2009, 01:31:00 AM »
http://www.accessmylibrary.com/coms2/summary_0286-31210256_ITM


Quote
Correcting Excessive Headspace Conditions

Should you be dealing with a poorly made firearm, the best advice I have is to tell the owner to retire the thing and replace it with something more durable. Trying to make a silk purse from a sow's ear is the surest road I know to civil and possibly criminal liability. Excessive headspace is a common problem with these firearms. Sometimes it's due to wear and tear, sometimes to mistreatment, and sometimes to poor workmanship or improper materials used in construction.

Long headspace in a revolver that is not due to frame stretching often shows up as cylinder endshake. This can be corrected by adjusting the cylinder's longitudinal position on its axis by the use of shims, by swaging a groove on the axis, or by replacing the axis. Shims are available from Brownells and Midway USA, and a swaging tool (basically a tubing cutter with a dulled wheel) can be bought from Brownells or made by the enterprising gunsmith.

Semi-auto pistols will require barrel replacement.

Shotgun headspace problems due to chamber conditions (not related to worn locking surfaces or other moving parts) can best be corrected by using tooling and rim inserts by Clymer (available from Brownells).

Rifle headspace problems are corrected depending on the type of breeching system used. Most types of front-locking actions (such as Mauser-type bolt-actions, Remington bolt-actions, etc.) will require barrel setback or replacement. It is possible to correct headspace in some rifles by changing bolts, but this is usually a hit-or-miss proposition. (Exception: SMLE rifles had several different sizes of bolt heads manufactured in order to allow headspace adjustment over the expected rifle life.) I've also seen rifles that have had minor corrections made by hard-chroming the bolt face to build it up, but this can only compensate for a few thousandths of error.

Savage centerfire rifles using a locking nut to retain the barrel are the easiest on which to set headspace. Lock the receiver in a receiver wrench (a Remington 700 receiver wrench will fit) and clamp the wrench in your bench vise. Loosen the lock nut with a Savage wrench and back the barrel off a turn or so. Remove the extractor, ejector, and firing mechanism from the bolt. Then chamber a go gauge, and shut the bolt fully. Carefully screw the barrel in until it touches the go gauge (it will stop turning). Back the barrel off just a fraction and tighten the lock nut snug. (It doesn't need to be torqued until it squeaks.) The ideal position is where you can "feel" the gauge in the chamber as the bolt reaches the fully locked position, but absolutely no force is necessary to close the bolt. It takes a bit of experimentation, but is fairly easy to master.

Rifles that use tipping-bolt rear-locking mechanisms usually have their headspace adjusted by the expedient of changing the bolt's locking shoulder. This is a "crossbar" in the receiver that the rear of the bolt cams down in front of. Examples include the SKS, FN49, FAL, SVT-38/40, MAS 1949 and 49-56, Ljungman, and Hakim. If a replacement shoulder is not available, it's possible to weld up the existing unit and refit it. All applicable warnings about knowing your metallurgy and heat-treating methods apply here; if you leave the shoulder too soft it will wear out quickly, and if you leave it too hard it may shatter.

Rear-locking tipping-bolt rifles can also be modified by changing or refitting their locking shoulder. Care needs to be taken when addressing these rifles. That's because it's possible to set headspace properly while simultaneously having a dangerous amount of cartridge head exposure because the chamber is physically too shallow. It's important on these actions to ensure that the cartridge enters the chamber far enough that the front edge of its extraction groove is almost flush with the end of the chamber to guarantee sufficient support of the case head and web.

enfieldshooter303

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Re: fixing a headspace problem
« Reply #3 on: March 30, 2009, 01:58:41 AM »
SO BASICALLY ON LETS SAY A 1903 A3, ONE WOULD TAKE OFF THE BBL AND MILL DOWN THE THREADED END AND REDRILL THE CHAMBER THEN INSTALL THE BBL AND RUN A HS CHECK AGAIN?

SORRY ABOUT CAPS, THE BUTTON STICKS 8)

HK91-762MM

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Re: fixing a headspace problem
« Reply #4 on: March 30, 2009, 12:00:24 PM »
The 1903s have a cone at the chamber end .This makes it a bit hard  to set back --You need a lathe -You  calculate the distance the barrel turns  In with one thread -I think 03s are 1-10 square thread So you turn the shoulder back 100 thousanths this sets the sights straight up when screwed back on -Then you will need a chamber reamer and start cutting a new chamber -Go slow its a fine line to go to far only a few turns of the reamer..  You will have to cut back the cone feed and the extractor clearance .

Danjal

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Re: fixing a headspace problem
« Reply #5 on: March 30, 2009, 03:58:33 PM »
As doc's article said.. its dependant on the actual workings of the rifle.

http://www.accessmylibrary.com/coms2/summary_0286-31210256_ITM


Quote
Correcting Excessive Headspace Conditions

Should you be dealing with a poorly made firearm, the best advice I have is to tell the owner to retire the thing and replace it with something more durable. Trying to make a silk purse from a sow's ear is the surest road I know to civil and possibly criminal liability. Excessive headspace is a common problem with these firearms. Sometimes it's due to wear and tear, sometimes to mistreatment, and sometimes to poor workmanship or improper materials used in construction.

Long headspace in a revolver that is not due to frame stretching often shows up as cylinder endshake. This can be corrected by adjusting the cylinder's longitudinal position on its axis by the use of shims, by swaging a groove on the axis, or by replacing the axis. Shims are available from Brownells and Midway USA, and a swaging tool (basically a tubing cutter with a dulled wheel) can be bought from Brownells or made by the enterprising gunsmith.

Semi-auto pistols will require barrel replacement.

Shotgun headspace problems due to chamber conditions (not related to worn locking surfaces or other moving parts) can best be corrected by using tooling and rim inserts by Clymer (available from Brownells).

Rifle headspace problems are corrected depending on the type of breeching system used. Most types of front-locking actions (such as Mauser-type bolt-actions, Remington bolt-actions, etc.) will require barrel setback or replacement. It is possible to correct headspace in some rifles by changing bolts, but this is usually a hit-or-miss proposition. (Exception: SMLE rifles had several different sizes of bolt heads manufactured in order to allow headspace adjustment over the expected rifle life.) I've also seen rifles that have had minor corrections made by hard-chroming the bolt face to build it up, but this can only compensate for a few thousandths of error.

Savage centerfire rifles using a locking nut to retain the barrel are the easiest on which to set headspace. Lock the receiver in a receiver wrench (a Remington 700 receiver wrench will fit) and clamp the wrench in your bench vise. Loosen the lock nut with a Savage wrench and back the barrel off a turn or so. Remove the extractor, ejector, and firing mechanism from the bolt. Then chamber a go gauge, and shut the bolt fully. Carefully screw the barrel in until it touches the go gauge (it will stop turning). Back the barrel off just a fraction and tighten the lock nut snug. (It doesn't need to be torqued until it squeaks.) The ideal position is where you can "feel" the gauge in the chamber as the bolt reaches the fully locked position, but absolutely no force is necessary to close the bolt. It takes a bit of experimentation, but is fairly easy to master.

Rifles that use tipping-bolt rear-locking mechanisms usually have their headspace adjusted by the expedient of changing the bolt's locking shoulder. This is a "crossbar" in the receiver that the rear of the bolt cams down in front of. Examples include the SKS, FN49, FAL, SVT-38/40, MAS 1949 and 49-56, Ljungman, and Hakim. If a replacement shoulder is not available, it's possible to weld up the existing unit and refit it. All applicable warnings about knowing your metallurgy and heat-treating methods apply here; if you leave the shoulder too soft it will wear out quickly, and if you leave it too hard it may shatter.

Rear-locking tipping-bolt rifles can also be modified by changing or refitting their locking shoulder. Care needs to be taken when addressing these rifles. That's because it's possible to set headspace properly while simultaneously having a dangerous amount of cartridge head exposure because the chamber is physically too shallow. It's important on these actions to ensure that the cartridge enters the chamber far enough that the front edge of its extraction groove is almost flush with the end of the chamber to guarantee sufficient support of the case head and web.

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DRman

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Re: fixing a headspace problem
« Reply #6 on: March 30, 2009, 04:36:15 PM »
Please learn from my experience. DO NOT try to adjust the headspace on a bolt action rifle unless you are a very good machinist or a qualified gunsmith. It takes serious skill and know-how and can get you killed or blinded if you f*** it up.
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