I'll only carry after running a couple hundred rounds of range ammo through it and testing it with my carry ammo. Each mag gets several mags full.

For mags that hold more than six or seven rounds I test carry ammo by loading two at the bottom, two in the middle, and two at the top--filling the rest with range ammo. That way the mags get tested with carry ammo throughout their range w/o sending mags-full of expensive carry ammo down-range.

New mags: Same test protocol as a new pistol.

I would never even consider carrying an untested firearm--handgun or long gun.

I am part of the crowd that tests before carrying. I would only do otherwise if the only other option would be going unarmed. I prefer a hundred rounds and at least a mag of carry ammo through each mag. With a new Glock 17-19-26 , in a pinch I might be ok with full mag with each mag and a mag of carry ammo if the above had no malfunctions. My P320 has been flawless out of the box for about 400.

For a carry gun I feel comfortable with it after at least 200 trouble free rounds, but preferably 400 or more. I think it's important that this includes a couple boxes of your carry ammo.

150 rds ball and 60 rds of s,d,
unless you have a jamb.

then additional

Absolutely must test it first, with both fmj and hollow point. Test all mags as well. Chances of ever having to pull in a self defense scenario are slim but you better make sure it will go bang when you do.

I go with 200 rounds of ball and another 100 of carry ammo. I go with 200 because that was what Kahr used to recommend, not the best reason but it works for me.

My Sig MPX shipped without a trigger. I remember standing In the gun store looking at it and thinking how could a brand new firearm ship without a trigger.

I put several thousand rounds through my P365 before deciding to carry it. That said, it could easily fail at several thousand and one.

Of more interest is whether one should carry a firearm with which one is not proficient.

Given that proficiency is perishable, round count isn't nearly as significant as shooting enough to establish and maintain proficiency.

You may have to drive a bit but I can't imagine it would be that hard to find an isolated piece of land where you can run a few boxes through your new 365.

When I bought my 365 I considered all the rumors and such that were talked about. I was convinced that Sig had fixed everything but still fired 1200 rounds that BTW were flawless before it went into the rotation.

An aside on break ins. It depends on the gun for me. As a big H&K fan I usually just fire 300 rounds including 50 of my preferred self defense round since any machine can come not put together properly. BTW I have NEVER had any issue with a H&K or Sig for that matter. Now 1911's I usually give at least 500 rounds with more attention to JHP's since they can be more particular with no feed ramp unless a 9mm.

Minimum of a couple boxes of ammunition. If I experienced more than a failure or two, I wouldn't feel comfortable until a couple more boxes without any malfunctions that I couldn't attribute to my own error.