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Thread: headspacing 7.62x25, how much space do i need?

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    Gunco Member Camoguy's Avatar
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    Question headspacing 7.62x25, how much space do i need?

    I am about to headspace my 7.62x25. Without a go or no go guage I am going to use a live round. I have 2 types of ammo sitting around some Sellier and Bellot and some Yugo surplus from 1981. I measured several from each group and the S&B measures 1.366 avg and the surplus measures about the asme on avg. So when I go to headspace how much room should I leave. I was going to go with 2 thicknesses of Masking tape as go and 3 as no go ...will this work or am I way off?

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    Happy Camper hcpookie's Avatar
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    I hate to sound like stickler, but you should get a "no-go" headspace gauge... much cheaper than fixing an OOB explosion, or any hospital visit. Just isn't worth it IMO to guess.

    That said... ahem... you should be sure that the rim area of the cartridge is the only exposed area - this is where the thin sides of the case (blowout area) and the bottom of the cartridge (thicker area) begins. The idea for headspacing on the BACK of the cartridge is to ensure the thin-walled sides are almost completely covered, thus eliminating ruptured case problems.

    AK headspace is ~ .005" - that's a feeler gauge measurement. That's where the masking tape "trick" comes from. Personally I'd use a feeler gauge first. The fact that the 7.62x25 is a lighter cartridge doesn't eliminate the need to headspace properly. If you check a reamer company's website like Clymer, you can get the measurements for the chamber. Not sure if that would help.

    I'm still of the opinion that a headspace gauge is the best bet. You get it down to where a "no-go" gauge cannot close, and just loose enough that the action can close with an "average" factory round.

    Not sure if this helps. I don't think you're way off but like I said, I think gauges are cheaper than fixing broken guns... or faces...

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    Death Ray Operator vulcan762's Avatar
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    Masking tape compresses too much. use clear/frosted SCOTCH tape. Before I bought my 7.62x39 gauges I simply stuck tape on the back of a live round and put it into a known (good headspace) AK after removing the firing pin. After changing the thickness I got what I needed. As far as 7.62x25 I would say determine the amount of tape required for your AK then duplicate that thickness on the x25 round.

    What are you building anyway?
    Visit http://www.WeaponsWorld.comfor the current ammunition sale prices!

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    Gunco Member Camoguy's Avatar
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    Thanks Pookie...I know I should get a headspace guage but..... 7.62x25 isn't the most common round nad it may take many moons to save fot 2 gauges but I will look into it.
    Vulcan- I am building a yugo ak conversion chambered for the 7.62x25 round. Got a parrel done by Paneaca and an using a &4 bolt . Making it a locking bolt system with a reworked gas system so it will still cycle on that little round.

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    Gunco Member Golovko's Avatar
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    If you can only afford one gauge, get the GO gauge. You can always add 0.010" worth of shim material to make it function as as NO-GO. While not ideal, that method is still better than headspacing with a round that could have been manufactured either on the long or short side.

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    Gunco Regular Shadow Walker's Avatar
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    I always use the thickness of two pieces of notebook paper. It doesn't matter if I am headspacing 9mm Luger or .308 Win. I haven't had any problem yet.

    Of course, I have been known to use a long string for the first couple of shots. Check for primer setback, or case altering before shooting the firearm close up.

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    Gunco Rookie 3 WEELIN GEEZER's Avatar
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    Notebook paper? Live round? Does anyone measure these things before they try to use them as some sort of guage? I figger that notebook paper isn't exactly intended to be used like that so it could have quite a difference from the advertised dimension and from page to page. Whats the real measurment anyways? I will be making a ppsh43/suomi/ak47 frankenstein one of these days and am looking to get an idea what I should be looking for using real guages soon as I find some. I would hate to have my hard work . Or me . This or this is more like it.

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    Gunco Regular Shadow Walker's Avatar
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    The purpose of headspacing is to allow the action to work without forcing the cartridge into the chamber, while at the same time NOT having to much space between the cartridge case and the bolt face.

    Two pieces of notebook paper will allow enough space to prevent forcing the cartridge into the chamber, while at the same time NOT giving to much space between the bolt and the cartridge.

    Trying to accomplish more than this is a waste of time, and money.

    I use a long string when headspacing because I am a cautious person. I have never had any problems headspacing with this method.

    Think of all the money I have saved by not having to buy headspace guages for every caliber I have used this method with. That's enough money to BUY an AK.

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    Happy Camper hcpookie's Avatar
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    Quote Originally Posted by Shadow Walker
    The purpose of headspacing is to allow the action to work without forcing the cartridge into the chamber, while at the same time NOT having to much space between the cartridge case and the bolt face.

    Two pieces of notebook paper will allow enough space to prevent forcing the cartridge into the chamber, while at the same time NOT giving to much space between the bolt and the cartridge.

    Trying to accomplish more than this is a waste of time, and money.

    I use a long string when headspacing because I am a cautious person. I have never had any problems headspacing with this method.

    Think of all the money I have saved by not having to buy headspace guages for every caliber I have used this method with. That's enough money to BUY an AK.
    I don't mean to bust your chops, but it would be reckless to say that "anything more than 2 pieces notebook paper is a waste of time and money". Just isn't so... this is really as simple as reminding yourself to buckle up... just makes good sense.

    GRANTED - there are more properly-headspaced kits than improperly-headspaced, but they are out there.

    GRANTED - chances are that if you put the bolt to within .005" on top of a seated bullet, you'll probably be OK. But notebook paper just ain't the way to ensure .005". A spark plug feeler gauge, maybe.

    GRANTED - 7.62x25 carries a really really small powder load - not like a .50 BMG is behind the bullet!

    GRANTED - brand-new off-the-shelf ammo probably has enough strength in the walls to keep blowouts from happening. Not so with 500-year-old surplus of questionable origin...

    HOWEVER

    The problem is that headspace isn't just getting the trigger hole drilled straight, or drilling the holes on the wrong side of the receiver... you're talking the one CRITICAL measurement where the manufacturer determines the thin wall of that bullet is supported enough to prevent a blowout. And I mean a BLOWOUT!!!! GUNPOWDER burning (exploding) in the one area it isn't supposed to be.

    A PERSON CAN GET HURT if headspace errors lead to a blowout.

    Bottom line - just don't go there. Spend the $50 and sleep soundly knowing that every time you pull the trigger, your gun (and your face and arms) won't explode due to a ruptured cartridge blowout due to excessive headspace.

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    Gunco Regular Gunter's Avatar
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    Question on a PPS43/AK. The bolt/carrier is welded together and space off the left side of the trunnion. The recess in the 74 bolt is .013" deep. Using two different types of ammo, .156" of a case is left outside the barrel. So, if we subtract the two then there should be a gap of .143" between the face of the bolt and the barrel. Going with the .005" headspace, can you lock the bolt/carrier to the trunnion, and press the barrel in until a gap of .148" is left between the barrel? Would this not leave a headspace of .005"?

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