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Thread: Mod. 70 .338 w/BOSS

  1. #1

    Default Mod. 70 .338 w/BOSS

    I am looking at picking up a Mod 70 .338 stainless to replace my blued version. The rifle has the BOSS on it which makes the barrel to long for what I need it for. Does anyone have personal experience with cutting down the barrel and re-applying the BOSS? I have seen what the BOSS can do for accuracy and like it but do not want the added inches. I understand that a certain barrel length is needed for full energy (powder burn). What is the shortest length a .338 win. mag can be cut and still maintain full energy?

    Thanks in advance for your input.

  2. #2
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    The barrel without the BOSS will be 24" if this is the model I am thinking it is.

    Cutting down a less than 26" barrel defeats the purpose of the magnum cartridges doesn't it?
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    Member c04hoosier's Avatar
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    I would try screwing the BOSS off, putting a thread protector on there, and shooting it like that to see how well it shoots without the BOSS. If it shoots well, then there's no reason to cut the barrel down. You have just cut off 2 inches or so and didn't lose any accuracy. But if it won't shoot well like that, you should be able to hack a few inches off, re-crown, and re-thread the barrel. Shouldn't be too much effort or money.

    Also, for a .338 Win Mag, I would not go much less than 24 inches. Shorter than that you might as well just buy a .338 Federal or .338-06. You will get similar velocities, but you'll burn more powder, make more noise, and get a bigger fireball at the end of the barrel.

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    Member L. G.'s Avatar
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    Default Thread Protector?

    Got a source or link for one of these items?

    Pard has the excact same thing - stainless .338 w/boss. Looking to unscrew it when hunting in the field.

    He seems to think the rifle with have the same POI - I kind of doubt it. Anyone know?

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    Member shphtr's Avatar
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    Same POI? Prob not, but will need to shoot either way to make sure.

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    Member Float Pilot's Avatar
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    I had a 30-06 stainless M-70 with a boss, which was the least accurate rifle I have ever owned.
    Anyway I tried unscrewing the boss and the groups became HUGE no matter what handloads I tried. I sold that thing as fast as possible.

    But you might get lucky and get one that shoots well without the BOSS. Even if you had somebody trim off the threaded section and do a new muzzle crown, you wll only be loosing a half inch at most. The BOSS itself does not count as barrel and does not add any velocity.

    By the way, when I took off my BOSS, it shot (printed) about 6 inches off in another direction, at 100 yards.
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    I mostly respectfully disagree with the posts above particularly about the barrel length required for the 338 Win Mag.

    I have studied the 338 Winchester for decades and have found that it is not like the 300 Win mag or similar in that it's expansion ratio (bore size to powder capacity) is more like the 30-06 than the 300 mags.

    I have shot it in factory barrel lengths from 18" to 26" and have chronographed all these barrel lengths with many different loads. I also have cut a 28" barrel down to 18" chronographing every inch of it with different loads.

    I think the 338 Win mag does not need even 24" of barrel for peak performance. The loss of velocity per inch around 24" is about 20 fps from 22 to 26 inches of barrel.

    If I had a good model 70 in 338 mag, with a Boss on it, I'd cut the thing to 23" and try to forget the rifle was ever adorned with the hideous contraption. That is the ideal 338 Win mag barrel length.
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  8. #8

    Default Good feedback

    Thanks for the info. That's the stuff I'm looking for.

  9. #9

    Smile the barrel length...

    I hunted with a 24" barreled Mod. 77 Ruger .338 for a few years and liked it, though it was heavy. Then I hunted with a pre-64 Mod. 70 "Alaskan" .338, it had a slender 25" barrel and it worked very well. Then years ago I got the bug and customized a Mod. 70 "Classic Stainless" in .338 mag. It has lots of bells and whistles and a 23" barrel. No, it does not drive those 250 grain bullets as fast as the 25" barrel did, but, none of the critters care. So I guese to my way of thinking, all of those barrel lengths worked fine and it just comes down to individual choice. Cause like I said, those critters won't know the difference!

  10. #10

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    I had the opposite experience with my .338wm and a shortened barrel.

    The fellow i purchased it from had the barrel cut down to 20". I chronographed a load I developed and found it lost over 250fps according to my reloading manual. I had Ruger install a new barrel, the same handload that was 2550fps went to 2800fps with a 225grn bullet.

    I'll keep the 24". The 4" loss in length was 62fps loss per inch in my case.

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    Member c04hoosier's Avatar
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    Murphy, my advice on 24" barrel wasn't based on scientific research, or even personal experience. My thought process is that if I want "magnum" performance from a rifle, then a longer barrel is usually going to give me that better than a shorter one. In other words, I'm talking about efficiency. I wouldn't buy a .257 WBY with a 20" barrel because that would be really inefficient. Might as well buy a smaller, cheaper, lighter .257 Roberts and get a little bit less velocity, but a lot more efficiency. It'll be easier to shoot, and cost a lot less to shoot.

    Same thought process here. That is what I based my recommendation on, but 23" might be perfect, as you said. I have no personal experience with the .338, so I cannot say for sure. Just talking generalizations...

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    Default I have the same rifle you are looking at...

    Model 70 stainless in .338 win mag with a Boss.
    I have had it new since the mid 90's.
    Tuned it in the first week and still shoots real good.
    I am not Murph so didn't try to squeeze every last ounce of accuracy out of it. It will put a few Black Talons in an apple at a hundred and fifty yards though.

    If the rifle is in good shape and the bore is good and the price is right, I would pick it up.

    I don't think anyone here has said the Boss is a bad thing, only that they themselves don't like it and that it should be removed, cut off, etc...

    I would get another one in a heart beat.

  13. #13
    Member Matt's Avatar
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    22"-24" without the boss and a good crown job.

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