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Thread: New barrel for an m305

  1. #1
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    New barrel for an m305

    I'm wanting to replace an old barrel on an m305with another. I picked this barrel up at a gun show from a gunsmith who replaced the one I bought with a match barrel. It's new, or so the smitty said. I got it so that I could continue to blast the cheap chineese steel jacket ammo. It was $120. I got the old barrel off and noticed that the old barrel had no chamfer around the chamber. This one did. I dropped the head space gauge in both and measured. This new one was .010 less from barrel face to the head space gauge, than the other. Ok. Less headspace is better until minimum is reached. What bothered me is that the brass from reloaded brass when slipped in would have a small portion (3/32 ? by naked eye, exposed) due to the chamfer. All my bolt guns have no part of the brass head exposed. Should I consider the barrel bad? Consider it a loss? I'll see if I can take a picture of it.

  2. #2
    GunNutz buzzmagoo's Avatar
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    If you could find a chamber reamer that should get you where you need to be !

  3. #3
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    Is the chamfer factory or added?
    OK, the GO gauge projects .010 further from the chamber than it does with the original barrel.
    How was the headspace when the original barrel was installed in the rifle?
    With an additional .010 projection of the gauge, is the bolt going to close on the GO gauge when the barrel is assembled to the rifle?
    Unless the chamfering is a great dramatic countersink, I don't think I'd worry - is it just enough to facilitate feeding?
    Remember that a casehead is solid for a ways. Would thin sidewall brass be exposed by the chamfer? Drop in a new case, see where the transition zone is relative to the chamfer.

  4. #4
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    I can not answer the question about when the chamfer was put in. I just noticed that the chamfer was there when I started to change the barrel.
    The smitty had the crown, chamber end (including the threads) and the gas port taped up.
    There is no hint of any marking on the barrel from a lathe chuck, but he could have wrapped cardboard around it.
    The headspace gauges are marked match grade, go- gauge is + .002, no-go gauge is +.004.
    I stacked cut feeler gauges on the back of the no-go gauge and got a reading of +016 in total.
    .016 headspace - .010 diferential brings the headspace to .006. Not perfect but not bad for an m305.
    I think that you are correct about it being there to help facilitate feeding. Nothing else makes sense.
    As to, would the sidewall of the brass be exposed? That's why I'm nervous about this barrel and why I have started this thread.
    I am starting to think that it may be factory and that the manufacturer in China may not have taken into consideration that non milspec brass could be shot in it. If this is the case, the rifles with the chamfered chambers may be dangerous to fire with regular brass.
    It is my understanding that the head of milspec brass is significantly thicker.
    I'm trying to upload a picture.
    Still working on the pictures

  5. #5
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    Take a commercial case. Section the head. Drop it into the chamber, and see where the transition zone is, relative to the chamfer.

  6. #6
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    I just sectioned the head and placed it in the chamber as you said. The place where the chamfer meets the brass is right where the brass thins out and typically case head separation occurs. Upon taking another look at the chamfer, I noticed the chamfer only goes as deep as the depth of the feed ramp into the chamber. I've decided to turf this barrel. I hope that these are not what is coming in on the new Norinco M305s. Thanks Tiriaq

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