That option for the magazine wasnt always available.
I kept mine original and therefor sought out the original mags.
To the op sorry for my miss information.
magazine link below.
AR10
ArmaLite AR-10 Magazines are proprietary magazines. Previously ArmaLite AR-10's used converted M-14 magazines (1st Generation). Today AR-10 Magazines (Generation II) come in many sizes. Each magazine will accommodate ammunition variants used on the AR-10 platform.
MAGAZINE CONVERSION KIT W/BOX
Unless you are in "ban states" where current production, regular capacity magazines from Armalite (i.e. - the Gen 2 mags) are not an option as they are illegal, the "conversions" and/or Gen 1 mags haven't been necessary in over a decade now, but if you are "choosing" to keep your rifle OEM and not upgrade a simple part to allow you to use far cheaper, more plentiful mags...so be it.
However, since Armalite began production of the "new" magazines which are superior in strength, design and function to the older conversion mags, they have made the conversion bolt catch available for sale to the public for all to take advantage of the new AND old mags where permitted by law. Hell, even ban states permit SOME of the new mags where capacity is decreased from the usual 20-rounds down to 15, 10 and 5 as dictated under each state's respective laws.
While I realize you said you want your rifle "original" and thus wanted the OEM mags, there is ZERO external/appearance differences between the new and old bolt catches and only VERY minor internal appearance/functional differences that many people would never perceive from a quick look (or even a detailed look if they didn't know what they were looking for). Armalite just modified the "finger"/"tab" on the bolt catch that is activated by a portion of the follower to engage the LRBHO (the old, conversion mags had the silly plunger, pop-out activator for the catch because of the smooth back of the M14/M1A mags while the new Gen 2 mags have a built-in rear rib in which a steel tab on the follower rides that activates the catch).
Its a worthwhile conversion to give you the same outward appearance of your rifle while allowing you maximum flexibility in terms of the mags you can run. This is especially true in today's culture/climate where, at least potentially, there is always a looming ban around the corner (federal or state) and being able to source from a wider range of mags for your semi-auto is desirable if you want/need more for a rainy day.
Either way...no offense intended toward you or anyone else in my previous post. Just didn't want there to be any confusion or misinformation spread on this topic as the whole "mag" differences (especially between Armalite and DPMS/KAC/Magpul pattern rifles) is often a dealbreaker for some who don't fully understand all the nuances of the situation.
