long range 7mm cartridges

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by ClickMonkey, Mar 22, 2011.

  1. ClickMonkey

    ClickMonkey Member

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    I've been looking into appropriate long range (1000 yd and under) calibers now for a while, trying to make up my mind for a new rifle. I saw on the sierra website that their advertised BC for a 7mm 180gr Matchking is 0.660 @ 1650 fps (!) compared to the .30 caliber 220gr SMK with a BC of 0.629 @ 2100 fps. This has certainly piked my interest and made me lean toward some sort of 7mm magnum for this build. The rifle will be almost entirely custom, with a lilja 3-groove barrel or schneider poly barrel if it's a barrel burner, so barrel seating and twist rates shouldn't be a problem for these heavy bullets. I also handload, so a lack of commercial loads shouldn't be a problem, though brass availability and price should be taken into consideration. This rifle will be used mostly for target shooting, but may also see informal competition and/or hunting use as well.

    Anyway, now that we've gotten those things straightened out and a caliber specified, which cartridge will be most effective at pushing these suckers downrange? I've looked through my handy-dandy Hornady Handbook of Cartridge Reloading (8th edition) and discovered the 7mm Weatherby Magnum. It's based on a shortened 300 Weatherby case and has all the other traits associated with it. According to Hornady it will shoot a 175 grain bullet at 3000 fps with approximately 4-5 grains less powder than a 7mm Dakota and approximately 10 grains less than the 7mm STW all from a 26" barrel, a significant difference. Whats more, the Hornady data for the Weatherby includes muzzle velocities up to 3100 fps whereas the Dakota and STW are limited to 3000 fps from the same length test barrel.

    Has anyone on this forum achieved the claimed velocities?
    Any caveats I have failed to mention?
    Does anyone have real-world feedback to share?
    Are there any other options I should look into?

    Since the weatherby burns less powder, it should prolong the barrel life over the other cartridges I mentioned, that's what attracted me in the beginning. Does anyone have feedback on this point?

    On a side note, will the weatherby fit into a .300 Win Mag magazine? the dimensions that hornady specified put it only 0.02" longer and the same belt diameter as the win mag, is this a significant enough difference to complicate feeding or loading?

    Also, I'm open to other ideas for in terms of calibers and cartridges if you make a good enough argument... :D

    Thank you guys in advance. Your expertise has been very valuable in the past and hopefully will continue to be in the future.
     
  2. Long Time Long Ranger

    Long Time Long Ranger Well-Known Member

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    I have a few 7mm wby's and 7mm STW's. Have shot them extensively since the 70's at long range. Yes the 7mm wby will get the published velocity. It is right between the 7mm rem mag and the STW. I have extensive loading data on these three. It is an excellent cartridge that I couldn't figure why it didn't catch on big. The reason is it was only offered in the Mk5 for all those years and at that price they don't sell like a cheap remington, winchester or savage.

    The 7mm STW will shoot faster than the 7mm wby. The 7mm STW is the one you want to build. It is an exceptional long range cartridge and I have used it's cousin the 7mm-300 wby to take animals up to elk beyond 1000 yards. Depending on which action you have the STW might need modification of the magazine to load long VLD bullets. The 7mm wby would fit just fine on your 300 winchester action and should feed well with the long bullets. Tell us which action you have and somebody on here can tell you how to modify for the long STW.
     

  3. Edd

    Edd Well-Known Member

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    Why do you place the Weatherby above the Remington? The cases I am currently using in my 7mm Rem are fire formed Weatherby cases. The Weatherby has a longer neck but the Remington has more capacity to the bottom of the neck.
     
  4. ClickMonkey

    ClickMonkey Member

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    I have not actually started on this build yet. If I were to go with the STW, I would need a magnum length action, correct? I was planning on using a borden rimrock LSR (remington pattern, long action), but haven't really decided yet. Borden doesn't offer a magnum length repeater in their rimrock line. I could always go with another action if necessary, though.

    The reason I'm hesitant on the STW is the barrel life. While none of the 7mm magnums are really exceptional in this area, I would like to prolong it as much as possible. If the Weatherby can reach 3000 fps with a 180 Grain bullet, I'm content. If it can do this with less powder than most anything else in its class, even better, no disrespect intended. I've also played with the idea of necking down and slightly shortening a .300 Win Mag, while lengthening the bearing surface on the bullet. Still hesitant about purchasing all the equipment necessary to do so however, and even more so on a design that has not been really tested before. What do you think?
     
  5. Long Time Long Ranger

    Long Time Long Ranger Well-Known Member

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    If you do that you have a 7mm wby with the standard shoulder. The 7mm wby is easier on barrels and will shoot well at long range, mine do. However if you take care of your STW it is worth doing. Brass is available now from other suppliers for the wby so you don't have to buy the expensive wby brass. Either really will do well. A little over 100 fps difference. The wby feeds better with long vld bullets seated to the lands. The Dakota is good but brass is expensive.
     
  6. ICANHITHIMMAN

    ICANHITHIMMAN Well-Known Member

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    I dont own an 7mm's but from what you said why dont you just keep cost as low as you can since that seams to be a concern as well as barrel life. You dont need all that power for paper so why not just stick with the 7mmRM?
     
  7. ewallace

    ewallace Well-Known Member

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    You stated "target shooting, but may also see informal competition and/or hunting use as well"

    I would go with a 7 WSM guys are having good results at 1000 yard bench rest with the 7 WSM. For just hunting I would go 7mm Dakota.
     
  8. TMR

    TMR Well-Known Member

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    The 7 WSM or 7 Rem Mag will reach 3000 fps with a 180 in a 26" barrel as well. Less powder than the Weatherby and STW as well. I have built a bunch of 7's in the last couple years for guys and have alot of experience with the STW. Here are my findings:

    7 WSM: 180 Berger = 2950-3050
    7 Mag: 180 Berger = 2980-3100
    7 STW: 180 Berger = 3150-3200
    7 STW: 168 Berger = 3340 (28" barrel)

    This is based off my own data and information from guys that I have built them for. Keep in mind that my reamers may be different than others and could have an affect on velocities as well.
     
  9. Long Time Long Ranger

    Long Time Long Ranger Well-Known Member

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    TMR hit the nail on the head, it depends on reamers. The Dakota and the STW are the fastest of these. The weatherby and remington are next followed by the wsm. On average with same throat designs your looking at around 250 fps from top to bottom.

    With the ones I have shot 2900's are tops safely with the remington and wsm. TMR's reamers may allow for more velocity depending on throat design, etc. I was just speaking in general terms considering factory chamberings. I have never got 3000's with the remington or wsm in the ones I have shot. I have two 7mm remingtons and they top out in the 2900's absolute max with a 175 grain bullet. These are with 26" barrels. The STW will shoot 200 fps faster than either of these.

    As far as the 7mm wby with factory rifles it will average 100 fps faster than the 7mm remington. The Mk5 wby rifles chambered in 7mm wby have the wby freebore which adds velocity. Factory rifles offered in 7mm remington do not have freebore and are 100 fps slower on average than the 7mm wby. Loading manuals typically use factory rifles so there is your difference. With a custom reamer and varying throat designs all goes out the window. You can take 308 norma brass and neck it to make the 7mm remington, 7mm wby, 264 winchester, 270 wby, 257 wby, 338 winchester, etc, etc. They are all virtually the same case and capacity. Cartridges off this case can not compete with cartridges based off the full length H&H magnum case such as the STW's, 300 and 340 wby's, etc. You will jump 150-200 fps on avergae with this extra powder capacity. There are no free lunches. Look at case capacity and design and if those are similar performance will be similar. Throat designs and such can alter the velocity some but if somebody claims amazing velocity out of the ordinary somethings not right.

    I did not see where you said mostly targets and little hunting. But considering that I recomend the 7mm wsm if you want to stick with a 7mm. It has better barrel life, is extremely accurate at long range and a pleasure to shoot with lighter recoil. The short cartridge allows for plenty of room to allow for long vld bullets to be seated out to the lands. This makes it a good choice to easily do on any magnum action. If you are looking at long range hunting get the STW. It is cheaper and easier to get components than the Dakota. Either are excellent long range hunters.
     
    Last edited: Mar 23, 2011
  10. elkaholic

    elkaholic Well-Known Member

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    I'll throw another possibility into the mix. You might consider the .280 Sherman if accuracy, barrel life , as well as good velocity are your goals and all on an '06 sized case. The velocity is equal to the WSM with equal barrel lengths........Rich
     
    Last edited: Mar 23, 2011
  11. Flare

    Flare Well-Known Member

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  12. elkaholic

    elkaholic Well-Known Member

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    All else being equal, this is someone stating the impossible! The .280 A.I. is a very capable round but will NEVER attain as much velocity as a 7 mag. Its as simple as case capacity to bore (as I said, all else being equal). If that was the case, my .280 Sherman would definitely beat the 7 mag, and it won't!
     
  13. Flare

    Flare Well-Known Member

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    Well I would normally say that but too many people that I trust that have them are getting the same results. Sounds like it won't work but it does. I'm not familiar the Sherman round.

    Corey
     
  14. CHARLIEDUECE65

    CHARLIEDUECE65 Well-Known Member

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    I personally am looking strongly into the 7mm-300 Winchester Magnum. After reading about the accuracy, efficiency of this round it's gotten my attention. I currently have a new 7 rem mag with a 26.5" 9.5 twist krieger shooting 162 amax's very accurately. LTLR how does the 7mm-300 compare to the STW in regards to powder capacity, velocity, and accuracy.
     
    Last edited: Mar 23, 2011