Heavy 7mm Projectiles

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Wild_Bill, Jan 26, 2007.

  1. Wild_Bill

    Wild_Bill Well-Known Member

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    Hi i was asking for some info from Rich Machholtz at Sierra about the possibility of a 7mm projectile up there with BC like the 240gr 30 cal and 300gr 338 and this is his reply
    We just brought out the 175 grain 7mm MatchKing with a BC of .608 so I
    don't see another 7mm long range bullet in the very near future.
    If there is enough demand we'll build anything but we aren't there yet
    with the really big 7mms.
    Rich

    So if every one gives Sierra a call or email asking for heavier projectiles for the big 7mm's and a BC over .700 we might have a chance of getting a 7mm projectile that will keep the 7mm in the hunt with the balistics from Sierra.

    Cheers Bill
    Australia
     

  2. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Bill,

    Why not just get some 200 gr ULD RBBTs from Richard Graves and be done with it. They are already available, proven and kick the hell out of the .7 BC your looking for.

    I know shooting my lightweight 7mm AM loaded with this bullet at 3150 fps and comparing it side by side out to 1000 yards with my 338 Kahn loaded with the 300 gr SMK to 3100 fps with top loads, the 7mm shoots noticably flatter and is effected by the wind noticably less as well.

    Yes it would be nice if Sierra would give us a heavy bullet option as well but don;t hold your breath. Good thing is that there is a good choice out there right now.

    Kirby Allen(50)
     

  3. dakor

    dakor Well-Known Member

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    You will want to give the 180gr Berger a try. Posted bc at sea level is .673 but I feel I am getting closer to .710 myself.
     
  4. Wild_Bill

    Wild_Bill Well-Known Member

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    Hi Kirby i already have some 200gr Wildcats on order from Richard it would be great if their was also a comercial projectile that was up there as well as sometimes it is hard to get other projectiles in some countries and if your barrel does not like a particular brand you are out of luck. What twist are you using in your 7mm's with the 200gr i am looking at using an 8X68S RWS case improved and hopefully i will get them to 3000fps this is for long range F Class not hunting so it has to shoot under 1/2 MOA all the time and wind drift is a big issue and also recoil so if you step up to a 30 cal and use 240gr projectiles at that speed it becomes a lot harder to shoot them accurately as muzzle breaks are not allowed. Richard thought an 8.25 twist should be good. Also could you email me with your actual results as to the BC as i understand why they are not published it will give me a starting point to look at as my round will be slower the BC will also be lower.

    Cheers Bill
    Australia
     
  5. jeffbird

    jeffbird Well-Known Member

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    Bill,
    Bob Cauterucio makes a 7mm 176 gr with a bc of .74, and they are remarkably consistent.
    Jeff
     
  6. Wild_Bill

    Wild_Bill Well-Known Member

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    Hi Jeff do you have a email address for Bob Cauterucio?
    I would like to try some to see how they compare

    Cheers Bill
    Australia
     
  7. FRANK21

    FRANK21 Well-Known Member

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    I have a real soft spot for the 168/180 Berger VLDs.
    Excellent lot to lot consistancy, great BC, good performer on game.
     
  8. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Bill,

    More bullet options are never a bad thing, I totally agree!!! That said, I have yet to see a rifle set up for the 200 gr ULD RBBT not shoot them very well, impressively well to be honest.

    Your case should be just slightly less potent then a 7mm RUM. I think you will get your 3K fps with top loads. THe RWS brass is pretty stout stuff so you should get there without to much trouble.

    A 1-8.25 should easily handle that bullet in any conditions at the velocities you will be shooting in. Just make sure bullet baring surface compression by the lands is less then 20% or you may run into problems which I think we have already talked about.

    I have used 1-9 twists in every thing from the 7mm STW to my 7mm AM with these bullets and will say that out to 600-800 yards I have yet to see a problem in accuracy or consistancy.

    Past that, with the 1-9 twist barrels, accuracy seems to drop off noticably. Not dramatically but enough that at 1K I would not take a shot at a deer with my lightweight 7mm AM which shoots these bullets to 3150 fps comfortably in a 27" barrel.

    I can not say for 100% this is a stability issue or the fact that all the rifles I have shot these at that range with were light weight rifles and that just makes shooting them at longer ranges more difficult.

    I can say I have shot a 1-9 4 groove barrel at these ranges in my 7mm AM with these bullets and accuracy was extremely good. That was a 34" pipe and velocity was in the 3350 fps range. You will have to ask Buffalobob about that rifle, its his!!

    I have been working with Rock barrels on a special thin land 5R rifling design for this specific bullet and we have settled on a 1-8.7 twist as being just about as perfect as we can get for the 7mm AM.

    FOr your round, I would probably say a 1-8.5 would be totally adiquate for your needs but you will never see any issues with a 1/4" more twist at these velocity levels and in cool temps and high humidity, it will just give you that extra spin to make sure things stay on point at long range.

    I have no problem listing what I have found for BC testing these bullets in my rifles. That is because I state these numbers as what I have found measuring actual bullet drop over 1K yards. These are not what many would say are scientifically pure BC numbers but when you plug them into the ballistic programs, I can hit what I am shooting at out to very long ranges so something is working.

    I use .900 for a BC on my heavy 7mm AM rifle(3300 fps) and .88 BC for my lightweight 7mm AM(3150 fps). My customers have reported BCs ranging from .780 to .920 depending on the velocity they are using, altitude they are shooting at and pressure and humidity values.

    TO get started with your velocity levels from what I have seen in rifles such as the 7mm STW and the like, I would start with a BC of .850 to .880 and tweak it from there. They will most often get you within 1 to 1.5 moa at any range with these values to start with.

    Now to those of you that want to raise hell with these numbers, remember, these are only the numbers I have to plug into my Exbal program with my muzzle velocity and three acutal down range impact measurements from zero to get my prejected ballistic model to match up to actual bullet flight so take that for what you will. /ubbthreads/images/graemlins/grin.gif

    Good Shooting!!

    Kirby Allen(50)
     
  9. remingtonman_25_06

    remingtonman_25_06 Well-Known Member

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    The 176g Cauterucio, few questions. One, are these easily obtainable, and how much?? Two, how do they perform on deer size game? With a .74 BC, I am really interested in trying them out of my 7 RM. Its the highest BC 7mm cal bullet I've seen. Will they stabilize out of a 1 in 9 1/4"?? Thanks to anyone with the information.
     
  10. deerhunter7UM

    deerhunter7UM Member

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    180 bergers are the way to go! im runnin them at 3400 fps out of my 7 RUM. killed a whitetail this yr at 1515 and the bullet still did some serious damage killing it with one hit to the body.
     
  11. MagMan

    MagMan Well-Known Member

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    longgun7UM, can you give us some specs on your rifle and load.
     
  12. deerhunter7UM

    deerhunter7UM Member

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    win model 70 action with a 30" lilja barrel and im using 104 gr. of WC 872 around 3400fps with the 175 SMKs and the 180 bergers