extreme speed 7mm stw

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by redeye, Feb 12, 2011.

  1. redeye

    redeye Member

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    Got a consistant reading on my chronograph of around 3800fps with a 140gr Nosler sbt is this possible or do I need to get my chrony checked out?
    Redeye
     
  2. Long Time Long Ranger

    Long Time Long Ranger Well-Known Member

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    Max with a 26" barrel in 7STW with a 140 grain bullet is a little over 3500 fps. I think you got a bad reading.
     

  3. J E Custom

    J E Custom Well-Known Member

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    Unless you have a 30+'' barrel I would say you have a chronograph issue.

    A while back I built a stw with a 31.4 " barrel and tried to see how much velocity I could get.

    With the A Square 140gr loads (Listed at 3500 ft.sec) I got 3590 ft/sec but with hand loads I
    managed 3700 ft/sec with decent accuracy. but when I bumped it close to 3800 ft/sec the
    bullets failed.(Shed there jackets and accuracy was non existent).

    So if you are not having bullet problems then the chronograph is not correct.

    J E CUSTOM
     
  4. eddybo

    eddybo Well-Known Member

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    I got 3600+ with a 180 berger once and my chronograph was working good. The rifle did not ever work so well anymore. 7mm/338 LM does not mix with 95.5grs of 8208.
     
  5. Long Time Long Ranger

    Long Time Long Ranger Well-Known Member

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    JE, what powders are you using to get those velocities. My STW's are only 26" barrels and with five more inches of barrel you are going to be way faster. I was just wondering if I am using the wrong powder combos with the 140's. About 3550 for me and I am starting to flatten primers pretty good. I use mine pretty much for 800 yards and closer on deer-antelope size stuff so shoot the 140 class bullets quite a bit for flatter trajectory.
     
  6. redeye

    redeye Member

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    I was using 84.0gr of IMR7828, shot it today while the temperature was up around 70 degrees I did notice some splatter on the target.I figured I was on the edge when I loaded those rounds, this confirmed it. Went back and loaded some rounds with 83.5gr of Retumbo, speeds were back down to 3250 fps but the accuracy was excellent.
    Redeye
     
  7. Long Time Long Ranger

    Long Time Long Ranger Well-Known Member

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    I pulled out some of my loading notes on my 7mm STW's. One of my best accuracy loads with 140 grain bullets is 86 grains of 7828 producing 3547 fps average in my 26" barrels. One of my best loads with the 162 Amax is 83.5 grains 7828 at 3349 fps. With the 180 Berger 86.5 grains of H-870 at 3212 fps. Hope this helps some with where you are.

    I will add that with my 7mm-300 wby with a 28" barrel my accuracy load with the 140 grain bullet is 3645 fps and 3415 fps with the 162 Amax. It is very similar to the 7mm STW and was very popular until remington came out with the 8mm rem mag in 1977 and we all started wildcatting that case instead of the wby because of cheap remington brass. After nearly 20 years of strong popularity by many shops all over the country it was pushed by shooting times for standardization with the STW name. Factory remington 140 grain loads averaged 3469 fps out of my 26" barrels.
     
    Last edited: Feb 13, 2011
  8. J E Custom

    J E Custom Well-Known Member

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    I was using H 5010 and a compressed load (I think It was 91 to 93 grains but dont quote me on that)
    I will have to go back and look at my loading notes, I do remember that primer pockets did not
    last but 2 to 3 shots. and with poor accuracy I abandoned the heavy loads and settled for 3650 to
    3700 ft/sec.

    I also had some barrel issues and later re barreled the rifle with a 26" lilja and the velocity dropped
    back to 3540 ft/sec average and shot great. ( So much for the experiment to get higher velocity)

    J E CUSTOM