Is it legal to turn a high capacity Sig pistol mag into a 10 rd California compliant mag?  If so what do they require as far as being a permanent modification or acceptable modification?

You mean just use all those standard capacity mags that were bought during freedom week correct?

No but thanks for the help.  I will be sending two Sig pistols to my son as soon as he returns there from Afghanistan.  Jerk.

You used to be able to put a rivet in that would stop the follower at 10. I’m not certain if that is still applicable though.

You ask a question but give no details, a member replies with legitimate information, then you provide vital information and call him a jerk.

"Permanent" isn't defined in the law, and there is no reference to any special legal definitions located elsewhere, either.  

There's definitely disagreement on what constitutes "permanent".

You need to chill the fuck out, I gave you a solution to the problem you were asking about.  Go to google and type in “California freedom week” and see what comes up.  While you are at it you can also google the laws for reducing capacity of standard magazines to low capacity in CA if you want.  It’s amazing to me that arfcom thinks Californians are sensitive.

There are ways of getting around unjust laws without actually breaking any laws with a bit of creativity.

Is it legal?  Yes.  I seem to recall having read some discussions about conversions, possibly in the work up to the laws and later inclusions in the California Code of Regulations.  You could check with the CRPA and see if they have some information.  In the past, I purchased commercially converted mags which used blocks, rivets, etc.  My impression is the conversion is not supposed to be readily reversible, that is, not without destroying the magazine.  That would suggest a rivet that could be drilled out may not make it?  That's my impression.  I can't point you a spot in the laws or Code of Regulations that says that.

Legally, right now, one may not import or manufacture magazines holding more than 10 rounds.  There are licensed dealers that can do conversions and/or sell over capacity mags to authorized users.  That might be a possibility if having trouble finding the specific mags you need.  I suppose a Google search would turn them up.

The wink, wink, nudge nudge, idea that one can simply ignore the laws, is of course, not something I would suggest, remaining compliant with the CoCs.

Wow, someone’s having a case of the fucking Monday’s on a damn Tuesday.

Nothing is permanent.  Absolutely NOTHING is permanent.  It is a fictitious, falacious concept.  It is impossible to achieve.

Epoxy bonding can be reversed with heat.

Welding can be reversed with grinding.

Riveting can be reversed by drilling.

Screws can be unscrewed.

Cutting off can be reversed by extending.

Blocks can be taken out.

Have I mentioned 3D printing yet?

Show me a design (high cap or low cap) and I will show you how to reverse it.

I could go on and on.

Freedom week was fantastic!  It felt like a week-long party where the beverage of choice was freedom.