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Thread: When and why did the 30rd mag come about?

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    When and why did the 30rd mag come about?

    The title pretty much says it all. Why was the first AR mag 20 rds? When and why did the 30rd come about? Why is it curved instead of being straight like the larger capacity FAL/M14 30rd mags?
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    I'm interested to hear from those who know for sure also, buy my educated guess is this:

    The vertical stacking of tapered cartridges produces a natural curve. The curve in the magazine, AFAIK, is to prevent a nosediving of the rounds during feeding, which would cause hangups on the ramps. The effect is probably not so great in 20 round magazines to make a difference, but in 30's the curve seems to be needed.

    The more tapered nature of 7.62X39, for example, seems to me to be the reason why AK magazines are more curved than AR magazines, and consequently, why 7.62X39 does not work all that great with the straight magazine well of the AR.
    Last edited by a0cake; 03-23-12 at 12:16.

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    IIRC the first magazines started entering into service around 1969. There was alot of reluctance because 30 round magazines did not prove as reliable as 20 rounders.

    Of ccourse the AK magazines that we were seeing in Vietnam seemed to be working fine. Alot of it had to do with the way the magzines curve. AK magazines are considered "constant curve" and AR magazines are considered an interrupted curve.

    I believe that SAR did a write up on this several years back (maybe the Stoner interview).

    As for why they came about I would assume it was to increase the firepower available to the grunts on the ground and to reduce the amount of mags that had to be carried.



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    Quote Originally Posted by a0cake View Post
    I'm interested to hear from those who know for sure also, buy my educated guess is this:

    The vertical stacking of tapered cartridges produces a natural curve. The curve in the magazine, AFAIK, is to prevent a nosediving of the rounds during feeding, which would cause hangups on the ramps. The effect is probably not so great in 20 round magazines to make a difference, but in 30's the curve seems to be needed.

    The more tapered nature of 7.62X39, for example, seems to me to be the reason why AK magazines are more curved than AR magazines, and consequently, why 7.62X39 does not work all that great with the straight magazine well of the AR.
    That makes sense about the curvature, but then how well do 30rd M14 and FAL mags feed? Do they have issues since they're straight?
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    Quote Originally Posted by Iraqgunz View Post
    IIRC the first magazines started entering into service around 1969. There was alot of reluctance because 30 round magazines did not prove as reliable as 20 rounders.

    Of course the AK magazines that we were seeing in Vietnam seemed to be working fine. Alot of it had to do with the way the magzines curve. AK magazines are considered "constant curve" and AR magazines are considered an interrupted curve.

    I believe that SAR did a write up on this several years back (maybe the Stoner interview).

    As for why they came about I would assume it was to increase the firepower available to the grunts on the ground and to reduce the amount of mags that had to be carried.
    I think you just answered the OP's question!! The first 30-round AR magazine came shortly after, a soldier with a 20-round AR magazine encountered an enemy soldier, with a 30-round AK magazine. Especially, if the soldier was being fired upon by said 30-round AK magazine.

    The soldier came back and said, why can't we have these, too?
    Last edited by Lone_Ranger; 03-23-12 at 13:29.

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    Quote Originally Posted by Lone_Ranger View Post
    I think you just answered the OP's question!! The first 30-round AR magazine came shortly after, a soldier with a 20-round AR magazine encountered an enemy soldier, with a 30-round AK magazine. Especially, if the soldier was being fired upon by said 30-round AK magazine.

    The soldier came back and said, why can't we have these, too?
    Obviously more ammo in a single mag is a good thing (within reason) but I'm interested in the process of the evolution in design.
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    The first M16 magazines were 20 rounders simply because detachable box magazines that came before (M14) had a max capacity of 20 rounds.

    A 5.56 30-rounder is more curved than a 30-rounder 7.62 because the 5.56 cartridge has a steeper taper.

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    Quote Originally Posted by danco View Post
    The first M16 magazines were 20 rounders simply because detachable box magazines that came before (M14) had a max capacity of 20 rounds.

    A 5.56 30-rounder is more curved than a 30-rounder 7.62 because the 5.56 cartridge has a steeper taper.
    Huh?

    AK mag sure seems more curved than the AR mag.



    Last edited by SteadyUp; 03-23-12 at 15:17.
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    StG44 magazines- 30 rounds.

    M2 carbine magazines- 15 round with optional 30 rounders.

    The U.S simply had it's head up it's ass (especially post WWII) and the ability was probably there, not the mindset.

    Quote Originally Posted by danco View Post
    The first M16 magazines were 20 rounders simply because detachable box magazines that came before (M14) had a max capacity of 20 rounds.

    A 5.56 30-rounder is more curved than a 30-rounder 7.62 because the 5.56 cartridge has a steeper taper.



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    I've read somewhere that we didn't start using thirtys again until the round burst came out. I'll try and find the source but wanted to see if any of you guys have seen the same writing. Apparently because guys were wasting too much ammo fa with thirty rounders.
    Last edited by Ghost__1; 03-23-12 at 15:58.
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