jekla, let me try. The suggestion for formal training wasn't about being safe, but about context-based learning. You have asked a series of questions on the forum that have been quite vague and the query here is the same. Curiosity is great, but not only have your questions been vague, it would appear you haven't done much in the way of searching the forum for information even when the topics have been covered in some detail previously. So, not only are some on-line opinions likely to be insufficient, but without asking the right questons with the proper context, you aren't going to get the answers you need.
You are talking about your own personal protection, right? So why hamstring the forum members in answering your question by NOT providing relevant information?
"regardless of the mags capacity be it a preban 16rdr of the new 10 rd mags how many is enough for a gun? lets say the gun is your main piece. basically its for ccw/defense. not to be used in any ipsc or other matches."
First, you have not specified what type of gun or caliber you are talking about. So there is no real context about which an answer can be provided to you. I think you are talking about pistols, but there are some very small carbines and shotguns. Maybe you carry large or maybe you carry small. Maybe you carry a .22 and maybe you carry something in .50 AE.
Second, when it comes to defense issues, the capacities of the magazines is a salient point for many folks. A lot of folks feel that they can get by just fine with a single 15 (or more) round magazine that is double or even triple that of some single stacks. They choose high cap mags so that they don't have to carry spares. So, by writing off the mag capacity issue, you have killed another area of context that would be relevant to your query.
Third, you have provided not context for the carry of this gun. Is ths a general carry issue, work carry, carry around the house, and are you carrying in what you believe to be safe or unsafe circumstances? Are you a higher risk target because of the type of work you do or because you carry valuables. If I were a repo man or diamond merchant, I would likely be making some different decisions about carry from what I am doing now.
How many mags are enough? One, unless you need more and then one isn't enough. With no context, that is going to be about the best answer you are going to get that covers all the vague attributes of the query with a comparably inclusive vague answer.
"If you look through your scope and see your shoe, aim higher." -- said to me by my 11 year old daughter before going out for hogs 8/13/2011
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