The Lone Haranguer said:
On the 10-round Sig magazines I've seen (and used), the magazine body was shortened and a very deeply recessed floorplate was used to take up the space. It would not be feasible to make such a conversion to your existing mags. There may also be legal issues with using the full capacity bodies for a conversion as they could be converted back. I suggest selling the full-capacity mags and using the proceeds to buy some 10-rounders. You will probably find a ready market for them on this very forum's classifieds.
CA law [PC 12020(c)(25)(A)] requires large capacity magazines that have been reduced to 10 round magazines to be permanently altered to do so.
That's why some manufacturers used a short body magazine with an extended floorplate to make 10 round magazines.
Since it is legal to import magazine parts and possess magazine parts in CA...
I suggest you dissassembly your large capacity magazines into parts & never assemble them while in CA (keep them for use while you are in other states) and get the factory 10 round magazines for use in CA.
CA Penal Code 12020
(a) Any person in this state who does any of the following is punishable by imprisonment in a county jail not exceeding one year or in the state prison:
(2) Commencing January 1, 2000, manufactures or causes to be manufactured, imports into the state, keeps for sale, or offers or exposes for sale, or who gives, or lends, any large-capacity magazine.
(c)(25) As used in this section, "large-capacity magazine" means any ammunition feeding device with the capacity to accept more than 10 rounds, but shall not be construed to include any of the following:
(A) A feeding device that has been permanently altered so that it cannot accommodate more than 10 rounds.
(B) A .22 caliber tube ammunition feeding device.
(C) A tubular magazine that is contained in a lever-action firearm.
