David Tubb Final Finish Bullets

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by RDG, Sep 5, 2007.

  1. RDG

    RDG Member

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    Has anyone ever fire-lapped their barrel with these bullets and lost up to 200 fps. velocity. Why would that happen?:confused:
     
  2. Coyboy

    Coyboy Well-Known Member

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    RDG, no I haven't used the product.

    What caused the 200fps drop was the removal of barrel steel. The bullet is having an easier ride down the barrel thus chamber pressure is reduced. You might get the speed back at the cost of greater powder consumption.
     

  3. RDG

    RDG Member

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    Cowboy,
    I know but, they claim increased velocity.......
     
  4. RDG

    RDG Member

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    Cowboy,
    I know but, they advertise higher velocity......
     
  5. RDG

    RDG Member

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    Sorry! for the double posts!
     
  6. keithcatfish

    keithcatfish Active Member

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    I used FF in a .308 Win that fouled very badly but shot quite well (1/2 in). I haven't chronoed my loads, but with a book max load of Varget and a 178 A-Max, my primers (CCI) look just like they do when loaded with a starting load. I strongly suspect my pressure and velocity are low due to less friction in the bore. As such, I suspect book max can be exceeded without increased pressure. However, I would never advocate exceeding book max.
     
  7. RDG

    RDG Member

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    Cowboy,
    The rifle is a Remington 700 in 7mm Rem. Mag. ....I had to go
    up 4 grs. of powder to get my old velocity back......

    RDG
     
  8. Jeff In TX

    Jeff In TX Well-Known Member

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    Just guessing here, but here's my thoughts. I think you ended up correcting a problem moreso than creating one. I'm guessing you had a bad carbon build up in the throat area which increased your pressure of your former loads. Tubb's FF cleaned and polished the throat area putting your throat and barrel back to a normal state.

    I doubt you could lap the barrel enough with FF to lose 200 fps, but a bad carbon build up in the throat area could easily increase pressure enough to get an additional 200 fps.

    Other than the loss of velocity, how's the rifle shoot and clean since using Tubb's FF?

    Just my thoughts.
     
    Last edited: Sep 5, 2007
  9. RDG

    RDG Member

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    Jeff,
    I haven't shot it for accuracy yet. I've been just too busy here at shop.
    I will shoot it for accuracy. Because that's why i fire-lapped it.
    I was shooting a max load of Rel. 22 out of the nosler manual at
    3200 fps. with a 140 grain bullet. Now it shoots only 3000 with the exact same load. I'm now shooting 4 grains over max (nosler Manual) with no pressure sighns, to get my velocity back....Seems to me I shouldn't have to use 72 grs. of Rel.22 to get my performance...

    RDG
     
  10. Jeff In TX

    Jeff In TX Well-Known Member

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    RDG,

    Your current and past performance was effected by the use of Tubb's FF. I still stick with my first thought that the FF cleaned and polished your throat, removing the carbon build up thus decreasing the pressure.

    I think you ended up doing yourself a favor and extending your barrel life. See how it shoots and cleans, a loss of 200 fps isn't all that bad. In you need that extra 200 fps you've showed you can get it back with a bit more powder!

    Keep us posted after you shoot it.
     
  11. royinidaho

    royinidaho Writers Guild

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    What Jeff in Tx said......
     
  12. Mikecr

    Mikecr Well-Known Member

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    Whom ever suggested you'd get increased velocity was full of it.
    I've FF'd a dozen barrels over the years, and haven't seen a velocity change up or down.

    Jeff's probably right.
     
  13. goodgrouper

    goodgrouper Well-Known Member

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    After finding loads for many dozens of guns that had the FF treatment, I have found that it takes an average of 2 grains more powder to get the pressures back to were they were inititally. Some guns may take less, some more. But all cleaned easier, became accurate again, and extended their expected barrel life another 300-500 rounds. It is a real solution to a real problem.
     
  14. Coyboy

    Coyboy Well-Known Member

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    RDG, Jeff might have somthing with the carbon fouling, but this assumes you were not cleaning your barrel all that well. I believe the FF instructions tell you to start with a clean barrel and to clean between every abrasive coated bullet.

    I guess part of this comes down to how many rounds were down the tube before you FF? Or did you do this to smooth out a newer rough factory barrel? Did you use all the bullets in the kit? Was your intentions to make the barrel clean easier, or increase accuracy, or breathe new life in a well used tube?

    If it was a well used barrel, the throught was probably aligator skinned, and may have had a build up of stuborn carbon and copper within the checkering.

    Either way if you remove 3-5 ten-thousandths of an inch from your bore dia. even if it's only in the first few inches of the bore, the bullets will likly "slide" or engrave into the lands a little easier and with less pressure, causing a velocity drop.

    You may have differing accuracy results with bullets of thin versus thick jackets. Barnes and failsafes may not shoot as well as thinner jacket bullets. But this again depends on what happened internally when you FF the bore.

    Let us know how the accuracy changed, I am curious to see what happens.