how IMPORTANT is head space to a rifle?
- Thread starter JACK308
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Technosavant
New member
Too little headspace, the round won't chamber. Too much, and the extra space in the chamber means you're likely to have a blowout.
Generally the headspace is set when the barrel is installed, but if you have tolerances stack just so (the bolt locking lugs are at one extreme, the barrel at another), you can potentially have a headspacing issue even though the parts are technically in spec.
Unless you've installed a new bolt or barrel, it's generally something you don't worry about. Headspace has nothing to do with how you've loaded your rounds; it has to do with the dimensions of the chamber and how the chamber created by a particular bolt and a particular barrel compares to what it should be.
Generally the headspace is set when the barrel is installed, but if you have tolerances stack just so (the bolt locking lugs are at one extreme, the barrel at another), you can potentially have a headspacing issue even though the parts are technically in spec.
Unless you've installed a new bolt or barrel, it's generally something you don't worry about. Headspace has nothing to do with how you've loaded your rounds; it has to do with the dimensions of the chamber and how the chamber created by a particular bolt and a particular barrel compares to what it should be.
You are thinking of the over all length of the cartridge as in the amount of bullet sticking out I think?? That affects the accuracy, The pro shooters and the experienced hand loaders can explain it more.
If you are truely thinking headspace then Technosavant explained it already
If you are truely thinking headspace then Technosavant explained it already
I know someone with a 243 that the headspace is a thread too long.
He expands the necks with bigger ball, and then partial full length resizes to push the small shoulder around the neck back to the thread long position. Then he shoots the gun and it forms the brass.
This has been going on for years.
You would think it would be less work in the long run to pull the barrel and cut a little off the shoulder and the breech.
He expands the necks with bigger ball, and then partial full length resizes to push the small shoulder around the neck back to the thread long position. Then he shoots the gun and it forms the brass.
This has been going on for years.
You would think it would be less work in the long run to pull the barrel and cut a little off the shoulder and the breech.
Headspace is critical for safe functioning of a high power rifle.
The first consideration is the rifle case. The cartridge can only stretch so much than it will rupture. I believe I read it in Col Chin’s book that .006” is the standard maximum safe stretch. At least for a 20mm cannon round. After that the cartridge is highly likely to separate. The Brit’s called it case breakage if I remember right.
There is some confounding data out there, from P.O Ackley. He was able to fire 30-30’s without locking lugs and the case stayed put. I believe the chamber was very clean. Modern analysis of case stretching with a 308 shows how he got away with this.
http://www.thewellguidedbullet.com/mechanical_studies.htm "Yielding of brass case walls in Chamber" by James A. Boatright
Mr Boatright shows that around 25 K psia a 308 case head will stick to the chamber wall and hold the pressure. However above that pressure the side walls will stretch and if the case head is not supported, the case will rupture.
Another issue with excessive headspace is peening. Too much headspace and the case head will slam into the bolt face. This is a shock loading and can peen revolver shields, bolt lugs, receiver seats. It will be aggravated by low friction cartridges. I lubricate the cases used in my M1a. Eliminates case head separations which occur from case stretching on extraction. However I only set my shoulders back .003”. I suspect if I were to have more than .006” headspace difference between case and chamber I might have experienced peening. As it is, I am on my third barrel and everything is good.
Then there are issues with cases which are so long that they are a crush fit to the chamber. This is undesirable as it will cause an interference fit. The first problem is getting the bolt closed. You will read threads on this all the time, the guy does not use cartridge headspace gages to set up his dies and now he can't get the bolt to close. This will absolutely gum up a semi automatic mechanism. The second problem is getting the fat round out of the chamber. The interference fit will be worse after firing.
All modern rifles are checked for proper headspace at the factory. Surplus rifles must be assumed guilty till measured innocent, though if the surplus rifle has matching bolt and receiver numbers it is mostly likely OK.
Headspace is something that must be controlled between the ammunition and chamber for safe reliable functioning of a firearm.
The first consideration is the rifle case. The cartridge can only stretch so much than it will rupture. I believe I read it in Col Chin’s book that .006” is the standard maximum safe stretch. At least for a 20mm cannon round. After that the cartridge is highly likely to separate. The Brit’s called it case breakage if I remember right.
There is some confounding data out there, from P.O Ackley. He was able to fire 30-30’s without locking lugs and the case stayed put. I believe the chamber was very clean. Modern analysis of case stretching with a 308 shows how he got away with this.
http://www.thewellguidedbullet.com/mechanical_studies.htm "Yielding of brass case walls in Chamber" by James A. Boatright
Mr Boatright shows that around 25 K psia a 308 case head will stick to the chamber wall and hold the pressure. However above that pressure the side walls will stretch and if the case head is not supported, the case will rupture.
Another issue with excessive headspace is peening. Too much headspace and the case head will slam into the bolt face. This is a shock loading and can peen revolver shields, bolt lugs, receiver seats. It will be aggravated by low friction cartridges. I lubricate the cases used in my M1a. Eliminates case head separations which occur from case stretching on extraction. However I only set my shoulders back .003”. I suspect if I were to have more than .006” headspace difference between case and chamber I might have experienced peening. As it is, I am on my third barrel and everything is good.
Then there are issues with cases which are so long that they are a crush fit to the chamber. This is undesirable as it will cause an interference fit. The first problem is getting the bolt closed. You will read threads on this all the time, the guy does not use cartridge headspace gages to set up his dies and now he can't get the bolt to close. This will absolutely gum up a semi automatic mechanism. The second problem is getting the fat round out of the chamber. The interference fit will be worse after firing.
All modern rifles are checked for proper headspace at the factory. Surplus rifles must be assumed guilty till measured innocent, though if the surplus rifle has matching bolt and receiver numbers it is mostly likely OK.
Headspace is something that must be controlled between the ammunition and chamber for safe reliable functioning of a firearm.
as stated before, headspace isn't something you DO.
Headspace is a dimension, the distance between the face of the bolt, and whatever dimension "stops" the cartridge, whether it's the datum line on the shoulder of the case, or the rim, on a rimmed cartridge, or the case mouth, on most auto pistol cartridges. It is "set" when the barrel is either screwed into the action, or by the locking lugs of most autoloaders.
Too much headspace, and cases usually separate, usually with bad results.
Too little headspace, and SAAMI standard cartridges won't chamber.
You can purchase gauges, called go/no-go gauges for whatever cartridge you are shooting, and check the headspace, if you wish, but changing the headspace is usually a job for a qualified gun mechanic.
Headspace is a dimension, the distance between the face of the bolt, and whatever dimension "stops" the cartridge, whether it's the datum line on the shoulder of the case, or the rim, on a rimmed cartridge, or the case mouth, on most auto pistol cartridges. It is "set" when the barrel is either screwed into the action, or by the locking lugs of most autoloaders.
Too much headspace, and cases usually separate, usually with bad results.
Too little headspace, and SAAMI standard cartridges won't chamber.
You can purchase gauges, called go/no-go gauges for whatever cartridge you are shooting, and check the headspace, if you wish, but changing the headspace is usually a job for a qualified gun mechanic.
If you handload, and you're concerned about accuracy, you need to know the distance from the boltface, to the lands - as it relates to each bullet type you shoot.
Most "precision" shooters (I use the term loosely, as I still have a lot to learn) will experiment with bullet "jump"- the distance from the ogive of the bullet to the lands- because finding the sweet spot will result in maximum accuracy.
Two inexpensive- and indispensable gauges- will give you this information.
Hornady's OAL gauge, and Bullet Comparator.
I often exceed "max length" (as long as the round fits in the mag) with my loads using high BC bullets.
You never want to load too long, and jam the bullet into the rifling as it can increase pressure to a dangerous level.
Excessive headspace, if not caused by a massive overload that damaged the action, can be accomodated by setting the resizing die to the chamber length.
This is how: AFTER a case has been fired in a rifle with somewhat long headspace, it fits the chamber. The reloading die should be backed-off, so it only re-sizes the neck. Check the chambering and see if it still fits, then resize all cases, charge with primers, powder and bullets and fire them.
Again, re-size case necks and see how a case fits in the rifle. If it's a bit difficult to close the bolt, turn the die in a bit and try again. Keep turning the die in and testing until the bolt closes easily.
As brass is fired/reloaded several times, the brass will become more brittle, so the sizing die should be turned in a quarter turn at a time until it fits easily again. Lock that setting, as it should be fine for several more loadings.
This is how: AFTER a case has been fired in a rifle with somewhat long headspace, it fits the chamber. The reloading die should be backed-off, so it only re-sizes the neck. Check the chambering and see if it still fits, then resize all cases, charge with primers, powder and bullets and fire them.
Again, re-size case necks and see how a case fits in the rifle. If it's a bit difficult to close the bolt, turn the die in a bit and try again. Keep turning the die in and testing until the bolt closes easily.
As brass is fired/reloaded several times, the brass will become more brittle, so the sizing die should be turned in a quarter turn at a time until it fits easily again. Lock that setting, as it should be fine for several more loadings.
Gunplummer
New member
That was a very good question, but extremely hard to answer. There are so many variables involved that it really depends on the situation you are talking about. None of the answers posted are wrong, however they are not totally correct either. I am guessing that you want to know how head space affects accuracy? I suppose if you are shooting competition that demands the utmost accuracy with little brass movement, and repetition, then tight head space is critical. I have never really noticed a difference at a few hundred yards with a typical hunting rifle. A rimmed cartridge with a shoulder may have the head space called off the recess cut for the rim and the bolt face but it is not what I would call " True" head space. You guys with .303 British rifles know what I am talking about. Due to liberal war standards and extreme wear it is possible to have good head space on a .303 and be close to case separation. Head space is a very involved subject dependent on the situation.
While you are correct when it comes to obtaining optimum accuracy, the original poster is concerned about headspace. Lest we confuse him, we should state that headspace is unaffected by the distance from the boltface to the lands. It is controlled by the distance from the boltface to the chamber shoulders.
