Fire lapping and cryo-treatment

Discussion in 'Gunsmithing Forum' started by MisterMcCool, Aug 14, 2014.

  1. MisterMcCool

    MisterMcCool Well-Known Member Supporter

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    Just another way to separate a fool and his money?
     
  2. Txhillbilly

    Txhillbilly Active Member

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    And just why would you have that opinion?

    There are many shooters that have positive results with both processes. I'm a firm believer in the fire lapping process on barrels that have bad tooling marks in the bore.
    My Savage 110 FLP 25/06 had one of the worst barrels that I've ever seen.It shot patterns not groups when it was brand new,and would copper foul so bad in a few shots that it would take days to clean the copper out of it. I hand lapped the barrel twice with very little improvement,it would only shoot 100 grain bullets after that.
    I fire lapped it as a last resort before tossing the factory barrel,and that brought the rifle alive. It is a fantastic shooting rifle now.

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  3. MisterMcCool

    MisterMcCool Well-Known Member Supporter

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    I was reading about both processes and they sounded too good to be true.
    That's one yea on barrel lapping.
     
  4. Highpower

    Highpower New Member

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    I used a Krieger stainless heavy contour barrel when building my match AR. It was double cryo treated. Once before contouring the blank, and once again after. All Krieger barrels are hand lapped. The gun shoots better than I can is all I can say. How much (if any) of that can be contributed to the cryo process, I can't say.

    I also built a 1903A3 rifle using a NOS, short chambered, 2-groove Remington barrel that was still in the wrapper. After cleaning the barrel of all cosmoline and inspecting the bore, I was shocked to find rifling grooves that looked like they were cut with a dull butter knife. :eek:

    Horrible rough chatter marks that would shred a cleaning patch to bits when passed through the barrel. I spent quite a bit of time hand lapping the barrel until it was slick as snot. It's the best shooting 1903 I own. Go figure.

    Fire lapping can help, but it all depends on the condition of the bore that you have to start with. It's not going to bring a worn out barrel back to life.
     
  5. MisterMcCool

    MisterMcCool Well-Known Member Supporter

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    I thought that was the purpose?
     
  6. c3shooter

    c3shooter Administrator Staff Member

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    Worn barrel means oversized bore. Lapping- by hand, machine, fire or tongue- wears away material. Your oversized bore becomes even more oversize.

    However, if you have a good but ROUGH bore, It can help smooth the bore. Not a fix all for all problems.
     
  7. JonM

    JonM Moderator

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    My rra national match ar15a2 uses a cryo treated wilson arms barrel it shoots rings around every other rifle i have. I run it open sights and its a submoa rifle out to 300yards.

    Cryo wont make a shoddy barrel better but what it does do is stress relief a barrel allowing repeated shots to poa as the barrel heats up. It decreases poi shift from heat in a properly constructed barrel.

    Your average remington is going to see no benefit from the process. Taking a barrel off a rifle to have it cryo treated is probably not going to help. I wouodnt go out of my way to have it done as only the barrel maker knows if the composition of their barrels will benefit from the process or not.
     
  8. Highpower

    Highpower New Member

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    Metals contain internal stresses because of the way the raw material is formed through rollers or extrusion dies. Especially on the surface. If you remove a good portion of material from one side of a piece of cold rolled steel bar stock for example, the rest of the bar can warp like a banana.

    Now imagine having a raw barrel blank that has been bored though perfectly straight and true. Then you begin to remove the outer surface of the steel barrel blank in order to obtain a particular profile to fit the rifles stock. The stresses give way, the steel moves, and your perfectly straight bore is no longer straight. That is why barrel manufacturers have machinery to "straighten" barrels.

    Using cryogenics helps to reduce those residual stresses and helps to control unwanted movement of the material. The type of material used, and the order in which machining operations are done all play a part in how well well a barrel will hold it's proper "shape" through a range of temperatures.
     
  9. MisterMcCool

    MisterMcCool Well-Known Member Supporter

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    Wow, I never run across services that actually work. Maybe I shouldn't be so skeptical.
     
  10. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    Highpower, i understand cryo-treatment and have heard of fire-lapping, but could you go into some detail on how fire-lapping is done?
     
  11. robocop10mm

    robocop10mm Lifetime Supporting Member Lifetime Supporter

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    All the barrels for my Glocks, both factory and Lone Wolf have been Cryo treated. Alan my buddy at Sprinco has dome all of them for free. He send me an e-mail when he is about to do a cryo run and I drop a couple off.

    Stress removal is one benefit. It also toughens the metal. He has a contract with the USPS. He cryo treats brake rotors for them. Their own internal studies have found that a cryo treated rotor will outlast the vehicle. When they have to replace a rotor, they send the new one to him before installation. He has never gotten any negative feedback. The rotor NEVER fails
     
  12. Steel_Talon

    Steel_Talon New Member

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    I've done both and have been pleased with the results I was looking for.... But cryo for a regular shooter isn't for me....

    I make my own less aggressive lapping compound. A mix of lanolin, glycerin, and Diatomaceous earth. When I buy a used rifle I run a few rounds down the barrel to help clean things up a bit....
     
  13. Highpower

    Highpower New Member

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    You fire abrasive coated bullets through the barrel in order to smooth out any rough areas in the bore. Progressively finer grits are used to even out the scratches and "polish" the bore and rifling. Similar to prepping a rusted or slightly pitted outside of a barrel for a bluing job.

    You can buy bullets and/or loaded ammunition that are pre-coated with varying grits of abrasive, or you can buy kits to coat your own bullets.

    http://www.davidtubb.com/final-finish-loaded-ammo

    http://www.neconos.com/details2.htm

    http://www.midwayusa.com/product/646612/wheeler-engineering-bore-lapping-kit

    I've never used the fire lapping method myself. I prefer hand lapping where I can feel how the lap is moving through the bore, and concentrate on any tight/rough areas as needed.