Velocity question, 26-in barrel

Discussion in '7mm STW' started by hemiford, May 3, 2014.

  1. hemiford

    hemiford Well-Known Member

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    Sorry if this has been discussed, I read a lot of the posts here, but the thread
    with 4000 posts I haven't finished !

    I have two new take-off 26" STW barrels I got on Gunbroker (Rem700).
    My plan is to dedicate this gun to shooting 160-gr bullets. ( I shoot 140-grainers
    out of my 7 RM.) If I get a 7 RUM it will only see 175-180 grainers.

    So my question is, if I want more velocity than the factory ammo, how fast
    can I expect to get, keeping the barrel at 26" and the bullet at 160-gr ??

    I may get a longer STW barrel way down the road, but for now this is the
    package I'm going to work with.

    Thanks All !
     
  2. Truc

    Truc Well-Known Member

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    there are some cartridges that we can't match advertised velocity. but make no mistake accuracy is more important than 100fps. I found one for my rifle and the loading books said 3100fps but with a Magneto V2 chrono its only getting 2976fps but when it shoots like this who cares

    The single shot is from a 6.5 rifle which was my aiming point and three above is from my 7STW

    IMG_1561.jpg
     

  3. MudRunner2005

    MudRunner2005 Well-Known Member

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    The 7mm RUM is not really all it's cracked up to be, and I don't see it with any gains over the 7mm STW. I push 180's out of my 26" 7mm STW right at 3,000 fps, and it puts 5 inside a dime @ 100 yards. What more could you ask for?
     
  4. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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    The 7rum vs 7stw has twice the boiler room change of the 280 and 280 ai yet nearly everyone dumps on the 7rum. :rolleyes:

    Just had to toss that in there about the 280 as I know you like the 280ai so much Muddy!!

    I'm able to get a bit more from my 7rum than my 7stw but I'm actually shooting 140's in both at present since my heavy bullet load is flaky. With the 171 Barnes the 7rum was at start load at faster speed (3130 fps) than the stw was topped out (3100 fps). Unfortunately the Barnes isn't handling the speeds well in either rifle, so I'll have to play with other heavies.
     
  5. FEENIX

    FEENIX Well-Known Member

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    Have you tried .284 Caliber Bullets Custom Built for Accuracy | Matrix Ballistics VLDs in 168 or 190?

    Good luck!
     
  6. MudRunner2005

    MudRunner2005 Well-Known Member

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    Was that the 171 Match Burners?

    If your STW was topping out around 3100 with 140's, something is wrong... My STW pushes 180's right at 3K, and I'm still climbing the velocity ladder to see if I can get higher while staying in that node.
     
  7. hemiford

    hemiford Well-Known Member

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    After more reading, it seems 3200 f/s is hard to beat out of factory rifles
    with any 160 gr bullet, as a round number. I'm not trying for world record
    velocity of course, just seeing how big the performance envelope is.

    Wouldn't it be interesting if there was something like nitrous oxide for ammo.....
     
  8. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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    yep, the 171's.

    Actually, the 140 grain load I use has proven mild in my 7stw and I'll have to push it a bit to get 3300-3400 fps from it, but I don't really care as she shoots sweet loafing. I'm using a 24" 10" twist bbl. with a rather long chamber too, so you 9" twist guys won't hear what I land on for a full throttle load as it'll be slightly too much for your rifles. I actually am just going to push it to see where the top really is, and probably won't ever load there; it's good to know your cushion with a load.
     
  9. MudRunner2005

    MudRunner2005 Well-Known Member

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    My mistake...I thought you meant you were topped-out on velocity. I didn't know 140's would be that slow to keep accuracy. I would have figured 3200-3300 would have been easily do-able in finding another accuracy node.

    Yeah, at 71gr of 7828 SSC I'm not seeing any pressure signs with the 180's, and 3K fps is very nice. I might to bump it up to 71.5 to see if I can get an even 3,000 fps. Right now it's at like 2,965 or somewhere around there, figured another ½ grain oughtta bump it up that extra 35 fps, while still being inside of that accuracy node. Who knows, might even be slightly more accurate. I'll just have to try it and find out.
     
  10. Big Jake Duke

    Big Jake Duke Well-Known Member

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    My best load for the 160 class STW is 80 gr of imr 7828 and a fed match magnum

    primer. They run slightly over 3200. I just recently moved to the Nosler 150 LRAB. I think they are running closer to 3400. Great bullet, some ground squirrels were displeased with their arrival at silly distances.

    I havent had a clear chrono day with the 150s the speed was backed into by drop data.
     
  11. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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  12. Big Jake Duke

    Big Jake Duke Well-Known Member

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    QUOTE]

    year wasn't much further out (give or take a couple of yards from 480) as I wouldn't have had a chance once she started really dropping being off on velocity as I was.[/QUOTE]

    What speed were you actually shooting the 140s?
     
  13. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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    What speed were you actually shooting the 140s?[/QUOTE]
    3200 fps..
    The load seemed rather mild, but shoots well and I had a couple of hundred loaded from the old rifle, so I loaded a couple of hundred more. This rifle is a slower twist with a generous chamber, so she wants more go juice. It is also a 24" bbl., so the short barrel throws another variable in.