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Thread: .378 vs .375

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    Default .378 vs .375

    I am debating rechambering my .375 ZKK 602 to a .378 for long range work. The factory 25 inch barrel is just too long for a .375, and the ZKK magazine will accept .378 with out modification. Make Sense, or do I have"Magnum-i-tess"?
    I have a .358 Norma mag for a short barrel[21 inch] medium bore.

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    Member BrentC's Avatar
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    Quote Originally Posted by jim in anchorage View Post
    I am debating rechambering my .375 ZKK 602 to a .378 for long range work. The factory 25 inch barrel is just too long for a .375, and the ZKK magazine will accept .378 with out modification. Make Sense, or do I have"Magnum-i-tess"?
    I have a .358 Norma mag for a short barrel[21 inch] medium bore.
    I'd try the .378. Sounds like a fun project.

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    Default .378

    Be prepared for some really nasty recoil - much worse than the .375.

    Make certain the stock bedding is well prepared for the extra pounding also.


    Quote Originally Posted by jim in anchorage View Post
    I am debating rechambering my .375 ZKK 602 to a .378 for long range work. The factory 25 inch barrel is just too long for a .375, and the ZKK magazine will accept .378 with out modification. Make Sense, or do I have"Magnum-i-tess"?
    I have a .358 Norma mag for a short barrel[21 inch] medium bore.
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    Member 1Cor15:19's Avatar
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    Quote Originally Posted by jim in anchorage View Post
    I am debating rechambering my .375 ZKK 602 to a .378 for long range work. The factory 25 inch barrel is just too long for a .375, and the ZKK magazine will accept .378 with out modification. Make Sense, or do I have"Magnum-i-tess"?
    I have a .358 Norma mag for a short barrel[21 inch] medium bore.
    I personally have no use for a 378 Weatherby. If you have not fired one I would recommend that you locate a rifle and squeeze off a few rounds before you convert your ZKK. I am not doubting the 378's LR capabilities, but I am not convinced that the extra expense in powder (40-50% more), brass (normally 3-5$ a piece), and substantial recoil is worth the gain in external ballistics. I would suggest that you consider an "Improved" H&H if you are in the market for more velocity with your 375. You could go with the 375 Weatherby or the 375 JRS. Either offer 100-150+ fps and would be fairly easy to convert your rifle. Personally, I would select either of these over a 378.

  5. #5

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    I currently own two 375's, and I've owned a couple of 378's over the years. Everything said about it so far is pretty much on the money. It just took me a whole lot more shooting each year with the 378 to keep it "tamed." You definitely know you've corked off something with lots more whomp that the 375, and it takes lots of work to get all that under control. It can be done, but I wouldn't even think of a 378 unless you were going to shoot it LOTS. It's just not a casual use cartridge, even for confirmed gun nuts like me.

    I haven't shot one, but if I was looking for a little more whomp than the 375, whether or not the extra is really needed (I don't think so), I'd go directly to the 375 Ruger and not look back. I'm betting it's a whole lot more manageable than the 378 while still giving you plenty more than the 375.

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    Member Big Al's Avatar
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    I have never felt recoil like I felt from the .378 Weatherby. I would pick just ABOUT ANY OTHER CTG OVER THE .378 FOR A RECHAMBER . But then again it is a sure way to spend money on what will be your lest favorite rifle.
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    Moderator Paul H's Avatar
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    Default

    A .378 isn't a great long range round because there aren't any high bc .375" bullets. I've never shot a .378, but can appreciate the big fast recoil it would deliver and hence see absolutely no reason to get a .378. It's a great case when you neck it up to 50 cal, or run it as a 45 cal but downloaded from 460 performance to 458 lott levels.

    While the action can handle the added length of the .378 case, you'll have to have the bolt and extractor modified and likely the feed rails will need some work. I can't see having a .378 that didn't feed flawlessly, and expect that it will require a bit more than just a re-chamber and bolt face/extractor work to produce that.

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    Have PPG make you a tight reamer with a tight neck. Sounds like lotsa fun to me....

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    Quote Originally Posted by Paul H View Post
    A .378 isn't a great long range round because there aren't any high bc .375" bullets. ...
    The .378 does seem a little over the top, but there are a few high-B.C. .375 bullets, especially the Accubond and the 350gr TSX. Based on an Oehler chrono and the published B.C.s, my .375 Wby can do the following with factory ammo:

    375 WEATHERBY – NOSLER 260 GRAIN ACCUBOND (B.C. 0.473; 260 yd zero)
    Yds / Vel. / Impact / KE / Drift
    000 / 3040 / -1.75 / 5336 / 000
    050 / 2932 / 0.88 / 4963 / 0.59
    100 / 2831 / 2.52 / 4627 / 1.05
    150 / 2733 / 3.05 / 4312 / 1.83
    200 / 2637 / 2.43 / 4015 / 2.94
    250 / 2543 / 0.53 / 3734 / 4.40
    300 / 2452 / -2.70 / 3471 / 6.23
    350 / 2362 / -7.39 / 3221 / 8.44
    400 / 2275 / -13.63 / 2988 / 11.05
    450 / 2189 / -21.57 / 2766 / 14.09

    375 WEATHERBY – WBY 300 GRAIN NOSLER PARTITION (B.C. 0.398; 240 yd zero)
    Yds / Vel. / Impact / KE / Drift
    000 / 2830 / -1.75 / 5335 / 0.00
    050 / 2708 / 1.07 / 4885 / 0.64
    100 / 2595 / 2.70 / 4486 / 1.25
    150 / 2484 / 3.04 / 4110 / 2.28
    200 / 2377 / 1.97 / 3764 / 3.76
    250 / 2273 / -0.65 / 3442 / 5.73
    300 / 2171 / -4.96 / 3140 / 8.19
    350 / 2072 / -11.13 / 2860 / 11.21
    400 / 1975 / -19.32 / 2598 / 14.80

    Also, Superior Ammo in Sturgis said that they could load the 350gr TSX as follows:

    375 WEATHERBY – HANDLOAD 350 GRAIN TSX (B.C. 0.425; 222 yd zero)
    Yds / Vel. / Impact / KE / Drift
    000 / 2550 / -1.75 / 5054 / 0.00
    050 / 2444 / 1.34 / 4642 / 0.65
    100 / 2344 / 2.97 / 4270 / 1.30
    150 / 2248 / 3.01 / 3928 / 2.41
    200 / 2153 / 1.32 / 3603 / 4.01
    250 / 2060 / -2.24 / 3298 / 6.12
    300 / 1970 / -7.86 / 3016 / 8.77
    350 / 1883 / -15.73 / 2756 / 12.02

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    Default 260 noslers

    What are you trying to shoot? Pliestociene Short-Faced Bears or Tyrranosaurus Rex?
    My experience with the 375 with 260 noslers is very accurate for long range. 300 yards for caribou.
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    Premium Member MarineHawk's Avatar
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    Quote Originally Posted by Mkay View Post
    What are you trying to shoot? Pliestociene Short-Faced Bears or Tyrranosaurus Rex?
    Just shooting the only factory ammo available for my rifle. Preparing for a Sept. brown bear hunt. I could get by with less, but I like this rifle, and so far, i shoot it well.

  12. #12

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    Quote Originally Posted by tvfinak View Post
    Be prepared for some really nasty recoil - much worse than the .375.

    Make certain the stock bedding is well prepared for the extra pounding also.
    Well, that's one reason I want to keep the original barrel. It has a integral barrel recoil lug in addition to the normal receiver one.
    I appreciate all the input. I actually would prefer a .338-.378 but now we are looking at a new barrel.
    For those of you who wonder why I would do this, the 602 just seems wasted with a .375. Like a model 70 .22 hornet.

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    As others have said 378 recoil is some of the most vicious out there, I would rather shoot a 460 then a 378 any day.

    Another conversion you might think about that won't need bolt face work and will give you some more snort is going to the 375Ultramag.

    If you do the conversion definately get the stock glass bedded, recoil lug on the barrel or not, I've seen a bunch of the 416 and 458 CZ's with split stocks and even a few that were just 375s. It seems that the recoil lugs usually dont fit very square in their abutments and the screws touch in their holes under recoil, the stock then splits through the screw holes. I've also seen some less commonly I might add that split horizontaly when the front crossbolt is pushed back by recoil.

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    Premium Member MarineHawk's Avatar
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    I assume that the easiest conversion would be to the .375 Wby because of similar cartridge dimensions. It will add another 300 fps to you caretridge capibilities. As shown above, this does not equal .378 velocities, but it would allow you to fire a .350gr TSX that still is moving at almost 2,000fps (and over 3,000 ft-lbs) at 300yds. It also will allow you to shoot a 260gr AB such that it never rises significantly more than three inches above the line of sight and yet hits only 13.6 inches low at 400yds and, at that 400 yd distance, still hits with slightly more kenitic energy than a 30-06 produces at the muzzle. If that's a little too anemic for your needs, then never mind.

    FWIW, my Mk V DGR, all loaded up with bases, rings, and sope and removable bipod and mercury tube weighs in at a dainty 12 lbs, but it is far more comfortable to shoot than my 6.5 lb 12ga pump shooting 2-3/4" slugs.

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    Quote Originally Posted by MarineHawk View Post
    FWIW, my Mk V DGR, all loaded up with bases, rings, and sope and removable bipod and mercury tube weighs in at a dainty 12 lbs, but it is far more comfortable to shoot than my 6.5 lb 12ga pump shooting 2-3/4" slugs.
    That would do it. My 50-140 only tips the scales at 8 pounds, and with a 650 grain bullet and 130 grains of ffg black powder, it really, really rocks you back- more than either of the two 378's I've owned. But it's low velocity recoil, and actually fun. Weight and mercury would bring a 378 into line pretty quickly.

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    I have shot one and all I can say is OUCH! It will do the trick. I would stay with the 375. Just my 2 cents....


    Ron

  17. #17

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    Well looks like I am running more no then yes here, But since I have a gun crank's mind I am still in favor of a .378. I can go high on the weight since it's not a carry gun.[ boat/4 Wheeler]
    As mentioned, I have a .358 for carry all day work.

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    Quote Originally Posted by jim in anchorage View Post
    Well looks like I am running more no then yes here, But since I have a gun crank's mind I am still in favor of a .378. I can go high on the weight since it's not a carry gun.[ boat/4 Wheeler]
    As mentioned, I have a .358 for carry all day work.
    I have a friend that shoots a 378. It's a beautiful West German (J.P. Sauer) Mark V that actually belongs to an older friend of his. He has been loading 260 ABs at 2950+, or about the same velocity as the factory lists 300s. This makes the rifle significantly more comfortable to shoot and duplicates the various "improved 375s" such as the Weatherby/JRS/Ackley external ballistics. FWIW, he loves the rifle but does not care for the cartridge at all. It requires expensive brass (available on a limited basis and produced by one manufacturer) and uses more powder to achieve that velocity. However, it no doubt achieves that velocity at lower pressure than the various "improved" cartridges, but does so with a loss in magazine capacity. If you are set on a 378 I wish you well, but I hope you are not easily disappointed.

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    Premium Member MarineHawk's Avatar
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    Quote Originally Posted by 1Cor15:19 View Post
    I have a friend that shoots a 378. It's a beautiful West German (J.P. Sauer) Mark V that actually belongs to an older friend of his. He has been loading 260 ABs at 2950+, or about the same velocity as the factory lists 300s. This makes the rifle significantly more comfortable to shoot and duplicates the various "improved 375s" such as the Weatherby/JRS/Ackley external ballistics. FWIW, he loves the rifle but does not care for the cartridge at all. It requires expensive brass (available on a limited basis and produced by one manufacturer) and uses more powder to achieve that velocity. However, it no doubt achieves that velocity at lower pressure than the various "improved" cartridges, but does so with a loss in magazine capacity. If you are set on a 378 I wish you well, but I hope you are not easily disappointed.
    1Cor, has your friend hunted with the 260gr AB? If so, how did that bullet do?

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    Member 1Cor15:19's Avatar
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    Quote Originally Posted by MarineHawk View Post
    1Cor, has your friend hunted with the 260gr AB? If so, how did that bullet do?
    He has hunted with that behemoth of a rifle a good bit, but he has yet to drop the hammer on a living creature with the 378. My understanding is he thinks the 378 is almost as much fun to carry as it is to shoot. I'll report how it works, when/if he finally connects. He came into possession of a Model 71 (348 Win) a few years ago and he loves to hunt with that rifle so the 378 often stays at home.

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