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Thread: Checked my Factory Chamber with a Borescope

  1. #1
    Join Date
    May 2007
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    76

    Checked my Factory Chamber with a Borescope

    Had a look at my factory .22RF chamber with a bore scope, here is what I saw, the leade had some very light faint tooling marks where the rifling begins as well as about the first inch or so of the lands, I did not see any burrs on one side of the lands like I have seen photos of online,the grooves in the area just ahead of the chamber looked nice and smooth actually as well as the rest of the bore.I had just cleaned the bore with a brush and Rimfire Blend and could see no leading or carbon present and I did not see any lead on the patch's after cleaning the rifle . With that said are the tooling marks going to be a problem? I have shot the rifle but only a few shots to sight it in and one group at 50 yards before it got dark one evening the group measured .300" with Eley Match ammo. Is there any chance this rifle will perform ok with the tool marks present?. Thanks in advance.

  2. #2
    Join Date
    Feb 2003
    Location
    Tennessee
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    5,192

    Sounds OK....

    Before anyone could answer specifically, you'll need to say what you plan to shoot at with the rifle. The only difference in an hunting rifle and a target rifle is daylight and dark. Further, you haven't tested the rifle with different ammo and it seems you didn't have wind flags. The rifle very well could be a really good one! A .300 group at 50 yards ain't nothing to sneeze at with a factory rifle.

    If you plan to shoot casually, sell that borescope (just kidding) and simply enjoy shooting. If you plan to shoot competitively, sell that borescope (just kidding) and just say so - we'll help any way we can to put you in the winner's circle.

    Really though...depending on how that .300 went down. you may have a really good rifle.

    AND finally, If I'm way off base here just ignore this post as if it never happened.

  3. #3
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    May 2007
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    76
    I dont shoot competition,just shoot for a hobby,but like to try and get all the accuracy I can from a rifle

  4. #4
    Join Date
    Jun 2010
    Location
    Miss. Jones Co.
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    56

    You will see a lot in a chamber with a bore scope!!

    First thing is how many rounds have been put through the rifle? You talking about seeing the fraze on the side of each rifling, that happens when cutting the chamber but not as bad when you hob it out for a polished finished. The hob will smooth out the tool marks as you are bumping it up at low speeds in the lathe. You will see tear or tooling marks if it's just only been reamed, factory cut barrels. What kind of rifle is it you are playing with? This is some of the things I've seen in my years of working and building rifles.

    Rambo

  5. #5
    Join Date
    Jul 2014
    Posts
    6
    Quote Originally Posted by Rambo View Post
    The hob will smooth out the tool marks as you are bumping it up at low speeds in the lathe. You will see tear or tooling marks if it's just only been reamed, factory cut barrels. What kind of rifle is it you are playing with? This is some of the things I've seen in my years of working and building rifles.

    Rambo
    Rambo,
    Although I understand what a hob does and why, I am not a machinist. Could you explain what it looks like? Is it a type of finishing reamer or something abrasive like a stone or grinding compound.
    thanks
    ghgs

  6. #6
    Join Date
    Feb 2003
    Location
    Oregon
    Posts
    181

    Forget the term "hob".

    In machining a hob is used to cut gears. In this case the term is coming from a smith who makes up words for his tools and has inadvertently used the wrong term. Basically it is a very hard tool that has the exact same dimensions as the reamer that was used to cut the chamber but has no flutes. With just a little bit of gentle pressure it flattens the ridge tops of the tool marks left by the reamer and pushes that material down into the valleys forming a smooth surface. It removes no material. Google "burnishing tool" if you want a more complete explanation as that is actually what it is. If you think your chamber is to rough try something simple, short stoke a snug fitting patch using some Isso or Flintz. Try about 50 strokes, if it was cut with a sharp reamer it will polish up mirror bright. Every reamer leaves minor tooling marks, the sharper the reamer the smaller they may be but most of them get worn away after a few hundred rounds.

    Dennis

  7. #7
    Join Date
    Jun 2010
    Location
    Miss. Jones Co.
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    56

    You are right!

    Quote Originally Posted by Dennis D. View Post
    In machining a hob is used to cut gears. In this case the term is coming from a smith who makes up words for his tools and has inadvertently used the wrong term. Basically it is a very hard tool that has the exact same dimensions as the reamer that was used to cut the chamber but has no flutes. With just a little bit of gentle pressure it flattens the ridge tops of the tool marks left by the reamer and pushes that material down into the valleys forming a smooth surface. It removes no material. Google "burnishing tool" if you want a more complete explanation as that is actually what it is. If you think your chamber is to rough try something simple, short stoke a snug fitting patch using some Isso or Flintz. Try about 50 strokes, if it was cut with a sharp reamer it will polish up mirror bright. Every reamer leaves minor tooling marks, the sharper the reamer the smaller they may be but most of them get worn away after a few hundred rounds.

    Dennis
    In the oilfield business back some few years ago we had a machine that hobbed threads on collars, drill pipe and Hevi-Wate. But it went out quick as there was to many steps in getting the connections ready for threading. The term is used loosely for the hob!! Why does PTG call them a hobb if they are not a hobb?

    Rambo
    Last edited by Rambo; 01-23-2015 at 12:40 AM.

  8. #8
    Join Date
    Jun 2010
    Location
    Miss. Jones Co.
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    56

    You are smoothing up the lead or throat!

    Quote Originally Posted by ghgs View Post
    Rambo,
    Although I understand what a hob does and why, I am not a machinist. Could you explain what it looks like? Is it a type of finishing reamer or something abrasive like a stone or grinding compound.
    thanks
    ghgs
    All it does is irons out the tooling mark for a smoother finish, then when that is done you need to lap the bore some to get burrs or fraze by each rifling. You put in the tail stock of the lathe, turn the machine down as slow as it will turn, you use uncut pig fat and you bump it up as it turns slowly, just enough to iron out the tooling marks and then it will ready for lapping to get the burrs off the corner of the riflings. There is so much to this stuff as every little thing makes accuracy better!

    Rambo
    Last edited by Rambo; 01-23-2015 at 12:39 AM.

  9. #9
    Join Date
    Feb 2003
    Location
    Tennessee
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    5,192
    "There is so much to this stuuff as every little thing makes accuracy better!"

    I know what you meant but somehow feel the need to clarify. "Every little thing" might make matters worse.

  10. #10
    Join Date
    Jul 2014
    Posts
    6
    Thanks for the great explanations.
    ghgs

  11. #11
    Join Date
    Jan 2007
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    71
    Quote Originally Posted by Rambo View Post
    All it does is irons out the tooling mark for a smoother finish, then when that is done you need to lap the bore some to get burrs or fraze by each rifling. You put in the tail stock of the lathe, turn the machine down as slow as it will turn, you use uncut pig fat and you bump it up as it turns slowly, just enough to iron out the tooling marks and then it will ready for lapping to get the burrs off the corner of the riflings. There is so much to this stuff as every little thing makes accuracy better!

    Rambo

    Do you have to eat a heead cheese and vidalia onion sammich while doing this??
    Melvin Calliham

  12. #12
    Join Date
    Jun 2010
    Location
    Miss. Jones Co.
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    56

    Can't do 2 things at a time!

    Quote Originally Posted by Melvin Calliham View Post
    Do you have to eat a heead cheese and vidalia onion sammich while doing this??
    Melvin Calliham
    Melvin,
    I can't do two things at a time more less remember what happened yesterday. It all comes out to having chittlings and cornbread waitng for when you get done!!

    Rambo

  13. #13
    Join Date
    Jan 2007
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    71
    Quote Originally Posted by Rambo View Post
    Melvin,
    I can't do two things at a time more less remember what happened yesterday. It all comes out to having chittlings and cornbread waitng for when you get done!!

    Rambo
    Rambo,
    That sounds a lot better than head cheese!!!!
    Melvin

  14. #14
    Join Date
    Jun 2010
    Location
    Miss. Jones Co.
    Posts
    56

    Most of that is seasonal food Melvin.

    Quote Originally Posted by Melvin Calliham View Post
    Rambo,
    That sounds a lot better than head cheese!!!!
    Melvin
    Melvin,
    Most of this we are talking about is a seasonal food and a good bait is good to!! But once a year is enough for me.
    Rambo (Douglas)

  15. #15
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    Jun 2010
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    Miss. Jones Co.
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    56

    I'm still learning about this stuff!!

    Quote Originally Posted by ghgs View Post
    Thanks for the great explanations.
    ghgs
    Hey ghgs,
    I'm still learning this on these RF rifles, every little thing does help or hurt accuracy but this is so much fun to do!! Building a centerfire is no problem cause you can reload for it!! We will figure something out on them one day!!
    Rambo (Douglas)

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