7mm RUM for Long Range

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by JYuke, Jan 18, 2009.

  1. JYuke

    JYuke Member

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    First Off hello to everyone, been reading posts here for some time and decided to join.

    I did a search but came up with little so I figured this was as good of a place to ask.

    Do you feel the 7mm RUM is up to standards not in velocity, we all know velocity is no issue, but the fact its a bit pickey and unpredictable for reloading to make a long range hunting cartridge.

    I do own 2 in 700 actions, and have seen first hand how picky they are, however i found 2 loads that suit my needs on with 160s and the other with 140s, i would not call them tac drivers. but acceptable for hunting to resonable distances

    I am just looking for comments with regards to the 7mm rum, and what you found that works with this cartridge.

    Thank you
     
  2. gamedog

    gamedog Well-Known Member

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    Welcome to the forum!
    My 7 RUM shoots 180gr Bergers very well. If your looking to strech that caliber out, I'd consider shooting heavier bullets with higher bc bullets .
    You won't have the velocity, but the heavier bullets will perform better.
     

  3. eddybo

    eddybo Well-Known Member

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    What makes it picky and unpredictable, never noticed that. I have loaded for at least 4 different 7RUMs and found them to be very easy to load for using about 94 plus or minus grains of Retumbo with either the 160AB, 168 berger or the 162 hornadys.
     
  4. JYuke

    JYuke Member

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    I have found i can not get them as accurate as a 7mm rem, just are not paper puncher accuracy like you see with other cartridges. I have a hard time wih them, unless I expect too much.
     
  5. davewilson

    davewilson Well-Known Member

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    i would agree with the word "picky" and i would also agree with the 180 Bergers.

    what i found works with this cartridge is to make it a 338!
     
  6. J E Custom

    J E Custom Well-Known Member

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    The 7mm RUM is about the flattest shooting factory round on the planet and any time you
    have a large overbored case you will have a somewhat finicky round .

    But just like a hotrod engine it can be made to perform with some good bullet and powder
    combinations.

    I like to load 99 to 100% load density with all loads especialy the cases with 100+ grain
    case capacities.

    Also heavy long barrels work best in the big cases. The bigger the barrel normaly the less
    finicky they are.

    The main advantage of the big 7mm is it's ability to handel the heavest bullets better.

    Lets say you want to shoot 1000 yards. the 7 Rum will push a 175gr bullet 20" flatter
    than a 7 Rem mag can push a 160gr bullet an deliver 160 ft/lbs more energy .

    I have a sporter weight #4 conture 7 RUM that shoots consistantly in the .400 range
    and one of these days I will build one with a heavy( #7 ) 28" barrel just to see how well
    it will shoot.

    J E CUSTOM
     
  7. LouBoyd

    LouBoyd Well-Known Member

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    Re: 7mm RUM vs 338 RUM at Long Range


    The following is a "Quickload" comparison of a 338 RUM vs a 7mm Rum, both with 30" barrels, both with ~90% SAAMI max pressure using available powders picked for high velocity. In this example "long range" is 2000 yards.

    cartridge 7mm RUM 338 RUM
    Bullet 180 Berger 300 SMK
    Powder H870 91.8gn Retumbo 96gn
    Muz V 3170 fps 2725 fps
    2k V 1117 fps 1044 fps
    2k E 494 ft-lb 726 ft-lb
    2k drop 1568 inch 2033 inch
    2k wind 25.1 in/mph 27.1 in/mph
    2k TOF 3.32 sec 3.74 sec

    At some distance a higher BC projectile will have a flatter trajectory than one with a lower BC independent of initial muzzle velocity (within reason) . In the case of the 7mm RUM and 338 RUM however that distance occurs when both projecties are subssonic. The 338 needs more case capacity or higher pressure to equal the supersonic trajectory of the 7mm RUM than the 338 RUM case can provide.

    The 7mm RUM offers a flatter trajectory, a little lower wind deflection, and most noticably less recoil. The 338 RUM offers more delivered energy, larger holes, and longer barrel life.
    I woudn't bet on either to give best accuracy. on a given day. That would depend on a lot of factors incuding the atmospheric conditions even if the rifles and bullets were perfect.

    I don't own a 7mm RUM but I have a 7mm STW which shoots 180 Bergers and 338 RUM which shoots 300 SMKs. I built both for 1 mile silhouette and they are similar in design and weight. (Rem 700's, 29 & 28" barrel, HS stocks, no brakes. The 7mm STW is much easier to shoot because of lower recoil and typically gives better accuracy (for me). The 7mm STW case has less capacity than the 7mm RUM but it still gives a lower time of flight and flatter trajectory than the 338 RUM.
     
    Last edited: Jan 20, 2009
  8. davewilson

    davewilson Well-Known Member

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    not that there's a whole lot of difference, but i said i made the 7rum into a 338, not a 338rum. your comparison doesn't use the same case.

    what i meant was, a 338 is just a whole bunch easier to get to shoot accurately, than a 7mm. i also believe it can be shot more accurately in varying hunting conditions. i know it delivers a whole bunch more killing power and impacts are a lot easier to see.

    a 338/300 can shoot a 250 gr bullet at 31-3200. the 7mm version shoots a 180 at about the same speed.

    the reason it's better is because the 7 is just a VERY overbore cartridge. the farther away from overbore you are, the easier it is to get them to shoot and more consistant with varying conditions.

    the numbers you have are nice, if you're interested in 2k stuff. which it looks like you are. i really don't look at transonic, it's kinda BFD. way too far to shoot at game for me. well, maybe groundhogs. fun to play at rocks though!

    IMHO, in hunting situations, it's easier to make a killing shot with a 338, than a 7mm. the farther the distance, the more this holds true.
     
  9. Chopaka81

    Chopaka81 Well-Known Member

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    I am curious about the 7mm Rum. Does it have free-bore? Same question of the 7mmSTW?

    I have a donor 700 long action that I am wanting to have built into something that came push a Berger 7mm 168gr VLD to 3200fps.

    Am I dreaming?

    Don
     
  10. JYuke

    JYuke Member

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    No they do not have free bore, but they are too long to contact the lands and still feed out of the mag box.

    I have great luck with mine this weekend, after doing some work to them both, new stocks and bedding along with triggers..

    I am shooting 140 accubonds with RL-25 in the first RUM, for intermeadiate range shot 5 shots for .8 at 100 yards. Its no target rifle but the flinch factor always come to play with this big case no matter who shoots it, try as you might there is alot of jump.

    The second rifle did the same at 10 yards with 160 TSX bullets, and Retumbo powder about 95.0 grains. about .8, those last 2 shots lol! would have been better if i stopped at 3.