Chamber

[Newfie]

No need to get too far in depth with this one. Just want to make sure I have a good understanding about the chamber on a rifle.
I am guessing that once a chamber is cut and the barrel mated to the receiver that what you have is the best it will
Ever be. In other words speaking to accuracy, there is nothing that can be done other than getting the chamber as clean and smooth as possible. Correct or incorrect?
Also, can a chamber wear to become out of specifications in regards to diameter? My guess is no. The case of the round simple expands against the chamber wall when ignition occurs, correct? I can't imagine that the expansion would cause wear. Could ejection of the expanded case from the chamber after many thousands of rounds cause wear? Especially with steel cased ammo.
I realize a chamber could be lengthened thus increasing freebore but in my mind I see no benefit to accuracy. In fact could lengthening the chamber cause the bullet to have to jump to the rifling thus reducing accutracy?
Cpmments lease

[thughes]

Incoming dissertation from Mek in 3...2...1....

[Meketrefe]

LOL.. ok I will be brief...

No need to get too far in depth with this one. Just want to make sure I have a good understanding about the chamber on a rifle.
I am guessing that once a chamber is cut and the barrel mated to the receiver that what you have is the best it will
Ever be.
If it is well chambered with accuracy in mind then yes. But many are chambered just to be safe with a reasonable degree of consideration to accuracy but not too much
consideration to maximum accuracy unless they are chambered for that purpose.

In other words speaking to accuracy, there is nothing that can be done other than getting the chamber as clean and smooth as possible. Correct or incorrect?

What you want is the cambering to be true to the bore and w/o any run-out and properly headspaced to the bolt. The chamber has to be smooth and free of burrs or defects but
it must not be polished. they are finished with an emery cloth so the brass has a better grip as it expands.

Also, can a chamber wear to become out of specifications in regards to diameter? My guess is no.

Yes, some chamberings estrech with use especially if they are abused and/or with time and if the materials are not properly treated in a way that they did not break but also they gave in to tolerances. A chamber can also swell if not properly installed and depending on the caliber and rifle.

The case of the round simple expands against the chamber wall when ignition occurs, correct? I can't imagine that the expansion would cause wear. Could ejection of the expanded case from the chamber after many thousands of rounds cause wear? Especially with steel cased ammo.

Yes there can be wear with steel ammo but this is normally treated to reduce wear but some russian grabage surplus or tarnished can be more aggressive with time. And it is not just because of the steel that must be lacquered or coated but because folks shooting the types of firearms are used with this ammo they are not the best firearm caretakers so all the dust and debris contributest to teh abbrassion. One could also see swelling in cheap barrels or even on fancy thread relief that is cut too deep inside the trunion. It really depends on the firearm. Normally the rifling is gone before
any of the other issues can appear but they are not totally rare. After all a lot of the current surplus is garbage and military chambers were cut all over the place w/o too much dedication to detail so one could have one awesome and the next be totally off, still safe to fire, but not even close. Inconsistent quality.


I realize a chamber could be lengthened thus increasing freebore but in my mind I see no benefit to accuracy. In fact could lengthening the chamber cause the bullet to have to jump to the rifling thus reducing accutracy?

Extra freebore is done to allow for extra cartridge length (seating of the bullets further out) or to use a specialty type of bullet that could not be done with the original chamber. Sensitivity on the jump from the freebore to the lands depends more on the tolerances and the type of bullet, speeds and pressures. Some bullets are jump sensitive like those with secant ogive but those with tangent ogive might be ok with a larger jump. The increase in free-bore can have a very good effect in accuracy as it is normally done to allow for better match bullets that are more consistent and also show less drop and drift specifically in longer distances. The extra free-bore can also reduce starting pressures. Extra freebore must be given with an objective in mind. In some cases a tad extra freebore has drastically improved the performance of a round. I would start with the bullet choices and loading goals before touching a chamber.


I hope this helps.

[Newfie]

LOL.. ok I will be brief...

No need to get too far in depth with this one. Just want to make sure I have a good understanding about the chamber on a rifle.
I am guessing that once a chamber is cut and the barrel mated to the receiver that what you have is the best it will
Ever be.
If it is well chambered with accuracy in mind then yes. But many are chambered just to be safe with a reasonable degree of consideration to accuracy but not too much
consideration to maximum accuracy unless they are chambered for that purpose.

In other words speaking to accuracy, there is nothing that can be done other than getting the chamber as clean and smooth as possible. Correct or incorrect?

What you want is the cambering to be true to the bore and w/o any run-out and properly headspaced to the bolt. The chamber has to be smooth and free of burrs or defects but
it must not be polished. they are finished with an emery cloth so the brass has a better grip as it expands.

Also, can a chamber wear to become out of specifications in regards to diameter? My guess is no.

Yes, some chamberings estrech with use especially if they are abused and/or with time and if the materials are not properly treated in a way that they did not break but also they gave in to tolerances. A chamber can also swell if not properly installed and depending on the caliber and rifle.

The case of the round simple expands against the chamber wall when ignition occurs, correct? I can't imagine that the expansion would cause wear. Could ejection of the expanded case from the chamber after many thousands of rounds cause wear? Especially with steel cased ammo.

Yes there can be wear with steel ammo but this is normally treated to reduce wear but some russian grabage surplus or tarnished can be more aggressive with time. And it is not just because of the steel that must be lacquered or coated but because folks shooting the types of firearms are used with this ammo they are not the best firearm caretakers so all the dust and debris contributest to teh abbrassion. One could also see swelling in cheap barrels or even on fancy thread relief that is cut too deep inside the trunion. It really depends on the firearm. Normally the rifling is gone before
any of the other issues can appear but they are not totally rare. After all a lot of the current surplus is garbage and military chambers were cut all over the place w/o too much dedication to detail so one could have one awesome and the next be totally off, still safe to fire, but not even close. Inconsistent quality.


I realize a chamber could be lengthened thus increasing freebore but in my mind I see no benefit to accuracy. In fact could lengthening the chamber cause the bullet to have to jump to the rifling thus reducing accutracy?

Extra freebore is done to allow for extra cartridge length (seating of the bullets further out) or to use a specialty type of bullet that could not be done with the original chamber. Sensitivity on the jump from the freebore to the lands depends more on the tolerances and the type of bullet, speeds and pressures. Some bullets are jump sensitive like those with secant ogive but those with tangent ogive might be ok with a larger jump. The increase in free-bore can have a very good effect in accuracy as it is normally done to allow for better match bullets that are more consistent and also show less drop and drift specifically in longer distances. The extra free-bore can also reduce starting pressures. Extra freebore must be given with an objective in mind. In some cases a tad extra freebore has drastically improved the performance of a round. I would start with the bullet choices and loading goals before touching a chamber.


I hope this helps.

Yeah, you always help. Thanks.
I am guessing the emery cloth in the chamber give some mechanical foot so to speak for the cartridge to grip. Where as something like crocus cloth would be detrimental as it would be more of a polish with less foot.
I think We at her by has some calibers with a large amount of free bore. I guess that is caliber dependent as you explained.
Thanks for the Info.

[EvilD]

LOL.. ok I will be brief...

No need to get too far in depth with this one. Just want to make sure I have a good understanding about the chamber on a rifle.
I am guessing that once a chamber is cut and the barrel mated to the receiver that what you have is the best it will
Ever be.
If it is well chambered with accuracy in mind then yes. But many are chambered just to be safe with a reasonable degree of consideration to accuracy but not too much
consideration to maximum accuracy unless they are chambered for that purpose.

In other words speaking to accuracy, there is nothing that can be done other than getting the chamber as clean and smooth as possible. Correct or incorrect?

What you want is the cambering to be true to the bore and w/o any run-out and properly headspaced to the bolt. The chamber has to be smooth and free of burrs or defects but
it must not be polished. they are finished with an emery cloth so the brass has a better grip as it expands.

Also, can a chamber wear to become out of specifications in regards to diameter? My guess is no.

Yes, some chamberings estrech with use especially if they are abused and/or with time and if the materials are not properly treated in a way that they did not break but also they gave in to tolerances. A chamber can also swell if not properly installed and depending on the caliber and rifle.

The case of the round simple expands against the chamber wall when ignition occurs, correct? I can't imagine that the expansion would cause wear. Could ejection of the expanded case from the chamber after many thousands of rounds cause wear? Especially with steel cased ammo.

Yes there can be wear with steel ammo but this is normally treated to reduce wear but some russian grabage surplus or tarnished can be more aggressive with time. And it is not just because of the steel that must be lacquered or coated but because folks shooting the types of firearms are used with this ammo they are not the best firearm caretakers so all the dust and debris contributest to teh abbrassion. One could also see swelling in cheap barrels or even on fancy thread relief that is cut too deep inside the trunion. It really depends on the firearm. Normally the rifling is gone before
any of the other issues can appear but they are not totally rare. After all a lot of the current surplus is garbage and military chambers were cut all over the place w/o too much dedication to detail so one could have one awesome and the next be totally off, still safe to fire, but not even close. Inconsistent quality.


I realize a chamber could be lengthened thus increasing freebore but in my mind I see no benefit to accuracy. In fact could lengthening the chamber cause the bullet to have to jump to the rifling thus reducing accutracy?

Extra freebore is done to allow for extra cartridge length (seating of the bullets further out) or to use a specialty type of bullet that could not be done with the original chamber. Sensitivity on the jump from the freebore to the lands depends more on the tolerances and the type of bullet, speeds and pressures. Some bullets are jump sensitive like those with secant ogive but those with tangent ogive might be ok with a larger jump. The increase in free-bore can have a very good effect in accuracy as it is normally done to allow for better match bullets that are more consistent and also show less drop and drift specifically in longer distances. The extra free-bore can also reduce starting pressures. Extra freebore must be given with an objective in mind. In some cases a tad extra freebore has drastically improved the performance of a round. I would start with the bullet choices and loading goals before touching a chamber.


I hope this helps.

too long, didnt' read

[Meketrefe]

Yes the emery cloth is to provide more friction so when the brass expands with pressure there is a good grip and seal and it minimizes thrust on the bolt. as you know this is specially critical with blow back actions but one never polishes a chamber unlike the bore that might be laped to a glass like finishing. When you see casings with bullets sticking out even with long bearing surface those normally have a long freebore like the 30/30 for example. It is the specific design of the case and intended bullets that dictates that.

[Newfie]

Yes the emery cloth is to provide more friction so when the brass expands with pressure there is a good grip and seal and it minimizes thrust on the bolt. as you know this is specially critical with blow back actions but one never polishes a chamber unlike the bore that might be laped to a glass like finishing. When you see casings with bullets sticking out even with long bearing surface those normally have a long freebore like the 30/30 for example. It is the specific design of the case and intended bullets that dictates that.

Thanks, more than likely there will be other areas I will have questions about.
By the way, in my last post what I wrote was Weatherby. However this tablet that has a mind of it's own broke it down into several words.
Don't have the computer with me and I sure miss the keyboard.

[Meketrefe]

Thanks, more than likely there will be other areas I will have questions about.
By the way, in my last post what I wrote was Weatherby. However this tablet that has a mind of it's own broke it down into several words.
Don't have the computer with me and I sure miss the keyboard.

NP. My pleasure. Most Weatheby cases are belted magnums so they headpsace on the belt, I am sure you know.