FB vs. BT

Discussion in 'Reloading' started by daniel745, Mar 7, 2011.

  1. daniel745

    daniel745 Member

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    I'm having difficulty getting BT bullets to group as well as FB in my 7mm/08. I'd like to use BT due to more availability. Any suggestions?
     
  2. Trickymissfit

    Trickymissfit Well-Known Member

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    Under 300 yards the flat based bullets will do anything you want. I shoot a lot of boat tails, but I also prep my cases for them as well. A regular deburr tool is not what you want, and you need one with a narrower taper in it. I use a junk taper pin reamer, but K&M makes a really nice one. Also BT's often have a problem with the way the meet the seater stem. I've had to modify many of them in the past, but now you can buy different ones from the manufacturer. Looking in the Hornaday and Speer loading manuals I see a total of 21 different flat based bullets made between the two of them! Sounds like you need another dealer to buy bullets from.
    gary
     
  3. rscott5028

    rscott5028 Well-Known Member

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    So, what FB bullets are you using and what's wrong with them?

    What twist does your barrel have? BT's tend to be longer/heavier and require a faster twist to stabilize.

    What BT bullets have you tried?

    -- richard
     
  4. daniel745

    daniel745 Member

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    My preferred hunting bullet was a 140gr. Barnes X but I've run out, and they no longer make them in a flat base. I,ve tried the Nosler AB and a Sierra boattail but can't get the same accuracy.

    The rifle is a Ruger 77 MK 2. I don't know the twist, but you may have a point about not being enough to stabilize the boattail. I would not have thought it would be a problem with a 140 gr. but I could be wrong.

    Almost all of the premium hunting bullets I could find are boattail, except the Partition, which I may have to try.

    Thanks for the input.
     
  5. BigSkyGP

    BigSkyGP Well-Known Member

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    I personaly find Ruger barrels to be super picky, about loads. Bullets, powder, and case. One change, and have to retest everything.
     
  6. rscott5028

    rscott5028 Well-Known Member

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    You may be able to lookup your twist rate from the Ruger website or you can measure it yourself.

    Because Barnes bullets are all copper, they are longer than an equal weight jacketed lead bullet. Hence, you may need to step down in bullet weight to shoot Barnes from your rifle.

    This may still not be your problem as I would think most factory 7mm barrels would be fine up to the 150-160gr bullets. Nonetheless, you might want to try a jacketed lead 140gr BT from another mfg such as Berger. And, keep in mind that Bergers can be sensitive to seating depth. So, once you've dialed in on the powder side, you may need to tweak your seating depth.

    -- richard
     
  7. gr8whyt

    gr8whyt Well-Known Member

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    I found a .pdf file somewhere once-upon-a-time. I've found it very helpful at times, so I pasted it to a web site at:

    Rifle Twist Rate Chart


    -- gr8whyt
     
    Last edited: Mar 8, 2011
  8. rscott5028

    rscott5028 Well-Known Member

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    If this is the rifle (Ruger® M77® Hawkeye® Standard Bolt-Action Rifle Model 37123) then you should have a 1 in 9.5" twist.

    According to Shilen (Welcome to Shilen Rifles, Inc.) you would want a 1 in 9" twist for bullets heavier than 140gr.

    Since the Barnes tends to be longer than a typical jacketed lead 140gr bullet, you may be on the borderline. But, that's a swag at best. So, stabilization may or may not be an issue here. You can try plugging the specific values into JBM (JBM - Calculations - Drag/Twist) and see what they say.

    Berger recommends a 1 in 11" twist for their 7mm 140gr Hunting VLD which should be aok for your rifle.

    In any case, you may simply need to fall back to a good load workup procedure without taking short cuts.

    Also, like TrickyMisfit put it, there are a lot of FB bullets available for 7mm as well.

    Hope this helps,
    Richard