338 AM vs 375 AM?

Discussion in 'Long Range Hunting & Shooting' started by supercrossbmx69, Feb 12, 2011.

  1. supercrossbmx69

    supercrossbmx69 Well-Known Member

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    which would you professionals out there choose? according to the G7 ballistics chart using a 325 gr. RMB with a bc of 1.035 for the 338 at est. 3300 fps, and a 370 gr. RMB with a bc of .924 at an est. 3200 fps, the 338 has more energy and with a 10 mph wind the 338 only would be pushed 6 MOA vs the 375 would be pushed 8 MOA, which i dont understand because the 375 bullet weighs 45 gr. more, but the 338 bucks the wind better? and the 375 starts off with 8411 ft-lbs of energy and the 338 starts with 7857 ft-lbs of energy but at 2000 yrds the 338 has 1620 fps and 1893 ft lbs of energy, and the 375 only has 1416 fps and 1647 ft-lbs of energy. if this is all correct, considering good 375 bullets are way harder to find the 338, then why have i heard some people say they prefer the 375 over the 338? the only thing i can think of that the 375 has the advantage over the 338 is barrel life?
     
  2. RDM416

    RDM416 Well-Known Member

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    I just went through the same thought process in the last day or so and came up with about the same conclusion. I have a 338 AM on order from Kirby and checked in with him to see if I could still change to a 375 AM...... he said yes.

    I am a fan of big bore stuff and have several that would qualify, up to and including one of Kirby's 510 AMs. However, I came to the same conclusion. I am not seeing a real ballistic advantage to the 375, although I would expect some terminal performance advantage simply because of the initial larger caliber. There are lots and lots more choices for bullets in 338 and some like the 300 SMK are quite inexpensive. So, it comes down to barrel life seems to be the primary advantage......Oh, and the fact that I just want one!! :D
     

  3. Varminator 911

    Varminator 911 Well-Known Member

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    Super:

    Bullet weight has nothing to do with wind drift, it's all about BC and muzzle velocity. For your example the 338 wins on both counts. And the BC you posted are G1, not G7. For those bullets the G7 would be better.
     
  4. supercrossbmx69

    supercrossbmx69 Well-Known Member

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    Ok that makes sense thanks varminter
     
  5. trueblue

    trueblue Well-Known Member

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    Go with the 338.
    Unless you need more down range energy, I don't see the need to go with the 375's.
     
  6. FEENIX

    FEENIX Well-Known Member

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    Bullet weight is directly proportional with BC and inversely proportional with velocity.


    CAL WT BC(G1) BC(G7)

    .338RBTAL 225 gr. .773 .356

    .338RBTAL 250 gr. .846 .390

    .338RBTAL 275 gr. .918 .423

    .338RBTHP 300 gr. .892 .418

    .338RBTAL 300 gr. .979 .455

    .338RBTAL 325 gr. 1.035 .492

    .375 RBTAL 370 gr. .926 .451

    .408RBTHP 420 gr. .822 .411

    .408RBTAL 420 gr. .861 .430

    .416RBTAL 450 gr. .923 .445

    .50RBTAL 750 gr. 1.005 .502
     
    Last edited: Feb 13, 2011
  7. groper

    groper Well-Known Member

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    The BC of the 325RMB is VERY optimistic to say the least... in reality its alot less than 1.0 and over long range the AVERAGE BC, which is the number your interested in to input your ballistic calculator, is much less than this.

    The 370gr RMB in .375cal, has an average real world BC of about .87.
    The 350SMK in 375cal, has an average real world BC of .78.

    Having never shot the 338 RMB, i cannot give you real world numbers, but there is no way its over 1.0. Having shot numberous other bullets in 338cal including super slick solids, so far none of them have exceeded a real world BC of ~0.93 (which was a copper solid).

    So, id ask around for an experienced person that has ACCURATELY figured a real world BC for the .338 bullets before you "run the numbers" on paper and base your desicions on that.

    I can tell you tho, that with copper solids, the .375 cheytac wildcats whips the .338 cheytac wildcats in ultra long range ability. Out to 1000yds, (which isnt really long range for these calibers) you cant tell the difference between them.
     
  8. Colcalcipherol

    Colcalcipherol Well-Known Member

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    What .338 is capable of launching a 325 gr. bullet at 3300 fps? And can this be done without significant overloading?
     
  9. bman73

    bman73 Well-Known Member

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    My understanding is the 338AM is a 408 Chey Tac case necked down to .338 and is more than capable of these kinds of velocities. It makes a 338 LM case beside it look small. Check out Kirby Allen's web page and you can see for yourself, he makes some pretty amazing toys that one day when the wife isn't looking I'm going to get
     
    Last edited: Nov 26, 2012
  10. Colcalcipherol

    Colcalcipherol Well-Known Member

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    Send her on a shopping trip with enough money that she thinks she is getting away with something. That's my plan . . .

    I am currently in Afghanistan but before I return, I am going to have my "dream rifle" built and, hopefully, have it ready when I get home. My plan is to give my wife $5k and let her have her way so I can go dump 8 or 9k on a new toy.
     
  11. royinidaho

    royinidaho Writers Guild

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    338 AM vs 375 AM?

    My read on this is that they are both very similar with the exception of the 375 having an advantage in bullet weight. But when push comes to shove a game animal isn't going to know the difference.

    The 338 may be a bit more of a barrel burner. If used as designed, for hunting only, it'll last a couple of lifetimes.

    I went with the 375 AM simply because I finally got tired of "settling for" and went as big as I could imagine . . . and a 357 barrel was immediately available.:)

    The 350 SMK @ 3250 has about the same flight time as my 270 AM shooting 170s.

    Plus the Kirby built 375 AM is much more of a pleasure to shoot than my braked 338 RUM w/300s and its nice to shoot.
     
  12. laserflat

    laserflat Well-Known Member

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    Mr Roy, have you tried any of the CE 375, 400, or 425gr bullets? Is 3000fps possible with the 425gr CEB?
     
  13. royinidaho

    royinidaho Writers Guild

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    No, and I don't know. . .

    I'm pretty much over my tinkeritus as far as "trying" different bullets. Plus solid bullets give me the vapors.:rolleyes:

    The 350 SMK shoots exceptionally well and at my elevations is supersonic to 2700 yards.

    I'd be wasting barrel life, powder, primers and brass simply to put better numbers on drop charts.

    I'm confident, under well understood conditions and locations to 1200 yds and will by next season work up to the same level of confidence to 1500 yds hoping for a shot under 1k. The SMK will do it well if I can "make the shot.":)
     
  14. Kiwi Greg

    Kiwi Greg Well-Known Member

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    Yes out of a 375/408 imp that is very possible :)

    I have found basically the 350,375,400 & 425 CEB are ballistically indentical.

    As the speed goes down the BC goes up.

    I have shot the 350s & 425s back to back at 2050 & 2550.

    The windage was only 0.1 moa different according to my ballistic calculator & the bullet strikes confirmed that.

    So you can shoot which ever you or your rifle likes the most :)