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Thread: Why use taper pins (instead of roll pins) on gas blocks?

  1. #11
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    That is the pin hole.

    This is the barrel:


  2. #12
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    If I'm looking at it right, the G36 gas block doesn't have the front sight sling swivel or bayonet lug as part of its construction.
    Its a low block shrouded by bodywork that is only stressed by gas pressure pulses and the occasional bump of the piston if it comes back into battery a bit out of alignment.

    The M16 gas block is exposed to gas pulses also, along with the regular stress of a sling pulling on it and if not locked down well the potential for the whole thing to rotate if the side of the sight tower is baffed. Little things that happen dozens of times a day on a work rifle.
    There's even obscure incidences of people putting a bayonet on one and putting it to use on hard training targets or actual soft targets.

    In any event, its not really an apples to apples comparison as the M16 gas block has so much more going on at once while the G36 block is neatly tucked out of harms way under protective coverings and does nothing but channel gas.
    Last edited by GTifosi; 11-27-11 at 13:43. Reason: spelling

  3. #13
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    The G36 block has much more stress on it than an M4 because each shot jack-jammers the gas block.

  4. #14
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    Even if the Piston system imparts more stress on the G36s gas block than the DI on the AR, isnt the stress only being implied in one direction? It just seems like the FSB on an AR is being asked to cope with other sorts of multi directional stresses that the G36s block isnt exposed to at all. These may be nonfiring related stresses, but they are stresses none the less. The stress applied by bayonet use may not be taken very seriously today, but 50 years ago it was a very real consideration.

  5. #15
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    The 416 uses roll pins as well. They have a sling mount, bayonet lug and front sight.

  6. #16
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    Swiss SIG 55x series uses two large spring pins.

  7. #17
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    Quote Originally Posted by sgtrock82 View Post
    The stress applied by bayonet use may not be taken very seriously today, but 50 years ago it was a very real consideration.
    Sure - and the taper pins worked well. They are a little more tricky to drill as the depth maters. With a spring pin you just do a hole all the way through. I would consider the spring pins to be the more modern way to do it.

  8. #18
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    All excellent points guys, especially the bit on the 416, a pretty parallel application. Im interested in knowing if the roll/spring pins are in fact more durable or if HK used them because thats what they prefer to use. I can see them being lower cost from manufacturers standpoint, taper pins seem to be more labor intensive.

  9. #19
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    Spirol(R) pins come in light, standard, or heavy duty versions. So one can always find a pin to meet the requirement - either by using a larger diameter or going to a heavier duty version. It should not take much to secure a low-profile gas block that is protected by a rail.

  10. #20
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    Quote Originally Posted by rsilvers View Post
    With a spring pin you just do a hole all the way through. I would consider the spring pins to be the more modern way to do it.
    I would bet that the large groove in the barrel is machined when the gas port is drilled.

    Notice in many of these euro designs, there is no shoulder behind the gas block journal.

    The pin groove is the sole locating feature for the gas port.

    The gas block is pre-machined with the pin hole.

    Assembly should not require any special alignment jigs.

    Just fit them together and knock the pin in.

    The heavy duty 3/16" (.187") Spirol has a double shear strength of 4500 lbs, which is probably about 150% of a single 2/0 taper pin (can't find exact info), that seems like plenty.
    Last edited by Clint; 11-27-11 at 20:30.
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