Gunsmithing Polishing Chamber

[perazzisc3]

What signs indicate that a tight rifle chamber needs to be polished?

 

[Wannashootit]

Not sure what you're asking...
I don't "polish" a chamber, they're supposed to have a tiny bit of "texture" actually- so that the brass can grip the chamber walls when it expands on ignition. I use grey Scotchbrite, everyone has their personal preference.

Are you having issues with chambering a round/closing the bolt? If so, what type of ammo (factory?), or is it a hard extraction problem?

 

[Threadcutter308]

What signs indicate that a tight rifle chamber needs to be polished?

"Polishing" is not a solution for a "tight" chamber. As Wanna said above, there should be a little texture on the chamber for the brass to temporarily grip the walls upon ignition. There are many different ways of doing it, but personally, I use~ 200 grit crocus cloth on a slotted wood dowel to "crosshatch" the walls, similar to honing an engine cylinder. IMHO, the last thing you want is a polished, shiny bright chamber.

Now, as far as a "tight rifle chamber", can you be more specific ? Are you having problems with case chambering or extraction of your re-loads ? What is the specific problem you are trying to solve ?

 

[perazzisc3]

"Polishing" is not a solution for a "tight" chamber. As Wanna said above, there should be a little texture on the chamber for the brass to temporarily grip the walls upon ignition. There are many different ways of doing it, but personally, I use~ 200 grit crocus cloth on a slotted wood dowel to "crosshatch" the walls, similar to honing an engine cylinder. IMHO, the last thing you want is a polished, shiny bright chamber.

Now, as far as a "tight rifle chamber", can you be more specific ? Are you having problems with case chambering or extraction of your re-loads ? What is the specific problem you are trying to solve ?

After thoroughly cleaning the chamber and taking the first 10 shots the bolt does not go fully into battery and I have to push it in with my thumb.

 

[BearNaked]

I might be over stepping but it sounds like a brass problem to me. if i am then please disregard.

if not then this is what i do that works.

take a round that you know is having issues chambering, color the entire case with a black marker (dont half ass this, color the entire case so any mark is from the chamber), put it in the chamber and put a little bit of pressure on it to close. dont gorilla hand it but make sure its enough to leave a minor mark on it. pull out the brass and see where it scratched. this will tell you what you need to know.

1. mark on the bottom of the brass means that you need to run these through a small base die to size the brass down to the min of saami specs.(i do this with once fired LC due to the machine guns)
2. mark on the shoulder means that you need to bump the should back further than you are right now.
3. mark on the neck means your neck thickness is too much and may cause you to neck turn your brass.
4. if the round is loaded and causing this, check the bullet when you pull it out, if it is too long then there will be a ring around the ogive and that leads to two potential issues there.
   1. bullet is seated too long and is jamming into the lands.
   2. if it is factory ammo then your chamber might not be throat-ed properly. i just had to send my match barrel off since this was my issue on a new build.

I would check the brass first as it is the easiest thing to fix.

 

[perazzisc3]

I might be over stepping but it sounds like a brass problem to me. if i am then please disregard.

if not then this is what i do that works.

take a round that you know is having issues chambering, color the entire case with a black marker (dont half ass this, color the entire case so any mark is from the chamber), put it in the chamber and put a little bit of pressure on it to close. dont gorilla hand it but make sure its enough to leave a minor mark on it. pull out the brass and see where it scratched. this will tell you what you need to know.

1. mark on the bottom of the brass means that you need to run these through a small base die to size the brass down to the min of saami specs.(i do this with once fired LC due to the machine guns)
2. mark on the shoulder means that you need to bump the should back further than you are right now.
3. mark on the neck means your neck thickness is too much and may cause you to neck turn your brass.
4. if the round is loaded and causing this, check the bullet when you pull it out, if it is too long then there will be a ring around the ogive and that leads to two potential issues there.
   1. bullet is seated too long and is jamming into the lands.
   2. if it is factory ammo then your chamber might not be throat-ed properly. i just had to send my match barrel off since this was my issue on a new build.

I would check the brass first as it is the easiest thing to fix.

I appreciate help, thanks!
I will try what you suggested, I have and use a small base die.
I was thinking the chamber was too tight or the barrel extension was out of spec, now maybe the throat was not properly cut as you said or a combination of these.
Whats funny is the barrel and my load combination shoots great out to 500 yds.
If there are marks on the neck might this be an indication of throat trouble?

 

[Wannashootit]

Autoloader? Be more specific. AR-10? 15?
A headspace/chamber/OAL issue would be consistent and not present only after you've dumped a mag. If I understand you correctly this is not a "round specific" issue as any given round will chamber and fire on first use but issue arises on the hot rifle?

 

[BearNaked]

I appreciate help, thanks!
I will try what you suggested, I have and use a small base die.
I was thinking the chamber was too tight or the barrel extension was out of spec, now maybe the throat was not properly cut as you said or a combination of these.
Whats funny is the barrel and my load combination shoots great out to 500 yds.
If there are marks on the neck might this be an indication of throat trouble?

you are welcome. sometimes these things are really frustrating.

what kind of rifle are you using? any aftermarket barrel? ammo - factory or reloaded? Is the issue only coming after firing or it happens on the first round?

without knowing those things i wouldnt jump to any conclusions.

 

[perazzisc3]

Autoloader? Be more specific. AR-10? 15?
A headspace/chamber/OAL issue would be consistent and not present only after you've dumped a mag. If I understand you correctly this is not a "round specific" issue as any given round will chamber and fire on first use but issue arises on the hot rifle?

Autoloader, AR 10 chambered in 6.5 Creedmoor, barrel Ballistic Advantage (might be the problem)
after properly cleaning the gun, barrel and chamber. After the first 10 rounds is when issue occurs.

 

[perazzisc3]

you are welcome. sometimes these things are really frustrating.

what kind of rifle are you using? any aftermarket barrel? ammo - factory or reloaded? Is the issue only coming after firing or it happens on the first round?

without knowing those things i wouldnt jump to any conclusions.

Mega Maten build, 6.5 Creedmoor 22" Ballistic Advantage barrel ( might be the problem)
I have put together identical upper using a 24" criterion barrel (no issues.)

reloaded ammo.after properly cleaning the gun, barrel and chamber. After the first 10 rounds is when issue occurs.

 

[BearNaked]

i'm lost if this started to happen after the first 10 shots. hopefully some of these other guys can help you out.