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Thread: AK47 headspace Go, No Go, Field

  1. #1
    Boolit Master Idz's Avatar
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    May 2013
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    AK47 headspace Go, No Go, Field

    There seem to be lots of opinions on the 'correct' way to headspace a barrel in the AK trunnion. Looking at SAAMI specs for min/max lengths the 7.62x39 cartridge is 1.245"/1.252" and the chamber is 1.252"/1.262". SAAMI specs MIN and a MAX gages for headspacing at 1.252" and 1.262" which correspond to the GO and FIELD gauges. The NO-GO spec is set by the rifle manufacturer and falls in between MIN and MAX and is rifle specific. So when one purchases a NO GO guage it can be anywhere between 1.252" and 1.262". This explains why people have difficulty checking their rifles. Since SAAMI considers it safe to have a minimum length round in a maximum length chamber the maximum safe headspace is 0.017" for the AK47. Using masking tape (or better foil tape) on the end of a round one can easily get within 0.017" so the the expensive gauges ground to within 0.0001" seem a little overkill for an AK-47.

  2. #2
    Boolit Master
    nekshot's Avatar
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    I bet a bunch of those ak's are really generous in dimensions!
    Look twice, shoot once.

  3. #3
    Boolit Buddy
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    The AK in all its many forms is NOT a precise piece of equipment. Kind of a close enough cave man specs lol

  4. #4
    Boolit Master OptimusPanda's Avatar
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    This makes me wonder what the actual Russian spec is...surely they have their own metric gauges.
    It's only hubris if I'm wrong.

  5. #5
    Boolit Buddy
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    Gauge. ... more like bang no bang

  6. #6
    Boolit Buddy
    Join Date
    Feb 2018
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    So I posted this, which kind of pertains to the original post here, on some other forums and got yelled at and told to purchase the correct gauges.

    What do YOU guys think?? Here it is:

    I have a question. It just seems crazy how expensive headspace Go, No-Go, and Field gauges are, and sometimes they are even hard to find. 35 to 50 bucks seems to be the going rate, which to this poor boy, is nuts!

    Now I know this is a really "redneck", "bubba" idea, but I'll stick my neck out and pose the question anyway. Why couldn't you take a new brass case for whatever caliber/gun you are working with, and fill it with epoxy so that it is solid and can not deform. (Couldn't crush or change the shoulder datum.) Then glue a piece of brass shim stock or steel feeler gauge onto the base of the brass, of the appropriate thickness. Presto; a $1.98 No-Go gauge. Right? No?

    (I happen to be working on an AK.)

    Kindly comments appreciated....

    Vettepilot
    "Those who sacrifice freedom for security, have neither."
    Benjamin Franklin. (A very wise man!)

  7. #7
    Boolit Buddy
    Join Date
    Feb 2018
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    Note also, that if I made my $1.98 NO-GO gauge, I would verify its length with my Hornady headspace bushing and caliper setup before use. I really don't see how you could go wrong. After all, measurements are measurements....

    Vettepilot
    "Those who sacrifice freedom for security, have neither."
    Benjamin Franklin. (A very wise man!)

  8. #8
    Boolit Master Bazoo's Avatar
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    Vettepilot, if you had a cartridge check gauge for the caliber, I'd think you could use that and shim out the head to make a no go gauge.

  9. #9
    Boolit Buddy
    Join Date
    Feb 2018
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    Yeah, if I had a GO gauge, I could shim that to make a NO-GO gauge, but I don't have one. Why couldn't a new cartridge case serve a a pseudo-GO gauge, and shim THAT for a NO-GO gauge. After all, that is what a GO gauge does; ensures that a cartridge will fit....

    Vettepilot
    "Those who sacrifice freedom for security, have neither."
    Benjamin Franklin. (A very wise man!)

  10. #10
    Boolit Master Bazoo's Avatar
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    Well, a cartridge check gauge is normally at minimum chamber dimensions. A casing is going to be smaller than that. But you don't know how much smaller so you need something as a base to start for making a no go.

    You could measure to the shoulder on a case and let's say for example, it is .003 smaller than the deminsion listed for your cartridge in your manual, then you could shim out to a few .001 more. The measurement listed should be max allowable cartridge deminsion. That would get you pretty close for a good guess.

  11. #11
    Boolit Buddy
    Join Date
    Feb 2018
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    Yeah, or just reference the SAAMI specs, as mentioned in the original post in this thread, and work out the case from there as you say.

    But so many people say "OH! NO! You'll blow yourself up for sure if you don't use a 50 dollar, real, live, No Go gauge!!"

    Vettepilot
    "Those who sacrifice freedom for security, have neither."
    Benjamin Franklin. (A very wise man!)

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check