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  • #49984

    Lets face it, the AR-15 is the #1 carbine in the western world.
    Sales, production numbers, and accessories.
    There’s no escaping it, anywhere.

    With that comes improvement and controversy.

    Probably the biggest argument revolves around the magazines, P-Mags vs X.

    Don’t get me wrong, P-Mags are good, excellent but they have one bug if you’re a handloader.
    Because of the limited space available (mag well) to strengthen the mag by using more material, they had to reduce space internally. Just a matter of fact.
    By doing so, it also reduced usable bullet length for the loaded cartridge.

    So for those who use things like 75gr Match bullets, you have to seat them deeper than the manual recommends to start with, for reliable feeding. IF you’re using a P-Mag that is.

    Here’s a 75gr Hornady Match bullet loaded to manual specs of 2.260″ loaded into a P-Mag atop a bunch of Federal 55gr JSP factory loads for comparison.

    As you can see, with the case rim flat against the rear of the magazine, the bullet has mere thousandths to clear the front of the mag inside. Internal dimensions of 2.270″ leave little to prevent bullet damage, possibly deep seating the bullet unintentionally or damage to the mag itself during recoil from the bullet nose.

    Options are to deeper seat the bullet and increase bullet jump, possibly effecting accuracy or…..

    Using a GI style metal magazine.
    The GI mag used here has an internal dimension of 2.290″ front to back.
    And while the mag “dimple” that is supposed to keep the case shoulder rearwards while entirely adequate with 55gr bullets at “normal lengths, is entirely useless with the long 75gr bullets, except to stiffen the mag, however the GI mag still better for this purpose than the plastic for a couple of reasons:

    1. The bullets “pecking” at the mag body in recoil don’t damage the GI mag.
    2: The extra .020″ may not seem like much, but distance is your friend, any additional distance between the bullet nose and the mag body is good.

    Here’s a 20 round GI mag loaded with 75gr handloads at “book” length.

    One nice feature of the 20 round GI mags, they fit nicely in the back pocket of a pair of Wranglers.
    30’s, be it GI or P-Mags, not so much.

    I’m not giving up my P-Mags, they are excellent mags, especially for conventional ammuntion.
    But I’m not giving up GI mags either, for specialty ammo and certain uses, they are perfect.
    And it’s easy to tell the difference between defensive and hunting loads just by choosing the appropriate magazine.

    Profile photo of sledjockey

    Although my son is partial to the P-Mags, I only use the GI 30 rounders. The speedloader/stripper clip factor is high on my list of “must haves” when storing ammo, so that is also a big reason. I am also quite happy when something associated with a gun is either wood or some sort of metal – it just makes me happy……

    I like the reference to the 20 rounders fitting in a back pocket. That is quite true and usually forgotten, so good point. The cheap Condor chest rigs are just so simple and easy to use that I have long since foregone pocket carry of magazines if I can help it, though. There are even some nicer 3 mag rigs that fit nicely under a coat if you don’t want everyone thinking you are Mr. Tacticool Guy.

    As far as the available room for reloads, I have had this argument with my brother on several occasions. He has gotten into the habit of using the ID of his mags for the OAL of his loads no matter what bullet….. Yeah, don’t start – I know and have told him how stupid that is and he should use book specs…. /sigh

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