Troubleshooting a Model 300--Pics Added
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  1. #1
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    Default Troubleshooting a Model 300--Pics Added

    Greetings! New member, looking to help a friend get his older 300
    back into firing condition.

    The rifle appeared to be complete and in functional order, with
    exception of a missing buffer. I fab'ed one up from a synthetic
    wine cork, and it seems to allow full cycling of the action.

    The original HK magazine has secreted itself in an unknown
    location. My friend obtained a new magazine--unmarked,
    possibly a Triple-K or ProMag (?).

    We've gone thru the action (short of disassembling the
    trigger group), cleaned and lightly lubed.

    We're seeing two, possibly three problems, at this point.

    1. The magazine is problematic in feeding. Seems to
    require several attempts to chamber a round.

    2. The rifle will fire, and sometimes the bolt will lock back (even
    if rounds remain in magazine), with the fired case remaining in the
    chamber. Other times, the rifle will fire, and attempt to feed the
    next round from magazine, with the fired case still remaining in
    chamber.

    In both cases, the bolt is propelled to the rear, so (I
    assume) the fired case is extracting/"unchambering"-- at least
    partially, but not ejecting...

    The extractor seems a bit "loose", in terms of it's clearance
    for case rim. I'm not familiar with this style of extractor. Is
    it normal for the left side to lack a hook, and have only a
    slight nub (this is where I wish I took pics!), and the right
    (ejection port side) to have only a shallow hook?

    I'm guessing with the fixed/non-spring load extractor design,
    it can't be too 'tight', dimensionally, or risk acting like a firing
    pin...so his ejector may well be, A-OK...

    Ejection: looking inside the receiver, there's a rail that runs
    along left ("solid, non-ejection port") side of receiver. As
    the bolt runs back in recoil, that rail gradually encroaches
    into the bolt face. I'm guessing that is the ejector, yes?

    The ammo was CCI, jacketed with a red polymer tip--
    sorry, didn't note the specific type. Are the 300's
    picky about ammo, is there any one variety that seems
    to give better results?
    Last edited by Steverino99; 01-05-2020 at 01:14 PM.

  2. #2
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    Congratulations on a great rifle. With respect to your first question, I highly recommend using authentic hk 300 mags. They are expensive; you can find them on gunbroker. Usually in the $150-200 range. I have read that the promags have problems feeding. I do not use any of these, only authentic HK mags. With respect to the buffer, there is a company that makes them. There are two styles for the HK300. Since you do not have a buffer to go by, look at your serial number. Make sure you tell them what it is as there were some changes with the HK 300 over the years. The early rifles are 15,000 and below, while newer are 15000 and above. You can also tell by the stock of rifles. Here is a link to the company that makes the buffers: https://www.critrcall.com/h-k-buffer-plates.html. With respect to the extraction issue, extractors I believe they may still be available. I am at work and can not remember the hook on the extractor. Check Midwest parts or Numrich on line. I have never had any issues with mine extracting. I use CCI, but can not remember the type of CCI ammo. I can tell you later today or tomorrow what I have used, but have not had any problems and did not use the ones you have described. I have not read if they are finicky with ammo and like I stated, the type of CCI 22wmr I use have problems. Please post pics also.

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    Sorry on the previous post, but I left out: I have had no problems with the CCI WMR that I have used. Will tell you the type later, as I am at work.

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    There are a few places making HK 300 and Hk 270 replacement buffers and they are only $50 (gentleman above has the link) and i have shot them extensively. My HK300 (was NIB when i bought it ~ 7 years ago functions flawlessly. I got 7 orig HK mags with it so never used the replacement mags (and wont as i heard they are crap).

    What is the serial #, i seen a 300 extractor listed a few days ago but i think it was for a 15K serial number +. https://www.gunbroker.com/item/833140876

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    Thanks, gentlemen!

    I'll pass along the info regarding buffer & magazine availability.

    I saw the serial # but don't remember it--I believe it was below 7000.

    I'll try and get pics of the extractor, and post here.

    Is the ejection accomplished by the fixed rail inside the receiver?

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    Welcome to the site--- keep us updated!!!

    Tony
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    How's the extractor look?

    Additionally, this rifle is S/N 67xx.

    Troubleshooting a Model 300--Pics Added-extractor-02.jpg
    Last edited by Steverino99; 01-05-2020 at 01:26 PM.

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    Boltface crack; can be felt with fingernail. Not sure about pulling extractor (without
    bending it), so depth is unknown. Is this a common occurrence with 300's?

    Troubleshooting a Model 300--Pics Added-boltface03.jpg

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    I have never seen this before on the HK 300. All the ones I have seen have a smooth finish and not pitted like yours. Is that pitting caused by some rust, contributing to the crack? I would check Numrich for a replacement part if it is even available.
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  11. #10
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    Not mine, it is a friend's rifle. Don't know much
    about history/handling. The 'pitted' area showed
    no rust--just looked almost like some type of coarse
    blast finish.

    Does the extractor look like it's still serviceable?

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