If I could go back and do a few things over, their were a few guns I would have keep and not trades off over the years, a colt diamond back 22, a colt 1911, a colt 380, some s&w's, even ruger's, but you can't go back so now you just have to bang your head on a wall
The one do-over I'd take would be NOT selling the 4" S&W 629 ten years ago. I had a new family at the time and needed the money, but I've always missed it.
Sig Sauer p250C bi-tone .45 and OMG was it the worst firearm ever I really wish I could go back and buy something different if I could it would either be a glock 21 or 30 or a 1911
My first handgun purchase was a 6.5" Ruger Single-Six with both cylinders (.22lr and .22wmr) and I still have it so apparently I did pretty good! I don't own my first GP100....but the one I do have (4" fixed-sight, full-lug, GP100 in .357mag) is by far my favorite!
I've owned a few that I sold (Colt 1991A1 Officer's Model, Kahr PM-9, a few Taurus's, etc.) but only one do I regret selling...a 2.75" Ruger Security-Six that I traded for another pistol but later (4 days) I decided I really wanted that back and had to wait a day before I went in and it had sold that morning!
The biggest thing I'd redo is to not have waited 24 years after I turned 21 before buying my first hand gun. Or, at the very least, not waiting 10 years after moving out of California before getting into shooting. I had done a lot of shooting back in the 70s but then just walked away from it when my family moved to CA in 81. Lots of lost years there.
My first handgun was a Ruger MKII Government model. To this day it is one of the best I have ever shot. I did put a target trigger in it years later, but I was shooting tight groups before the trigger job. It allowed me to learn all the shooting fundamentals without developing any bad habits like flinching from the recoil. Back in the good old days, a brick of .22 was $5 and was within my budget at the time. My brother purchased it for me, I was not old enough. One of those Indiana things, you can own it under 21, but can't purchase it under 21. At 18 I had my first handgun and have never looked back. That was back in 1980 something.
My first center fire handgun was a Desert Eagle 44 magnum, I regret selling it later when my vehicle broke down and I needed money, but I don't regret the smile it put on my face every time I pulled the trigger. I purchased a Smith 629 44 magnum later to replace it.
I wouldn't change a thing. My first was a Colt Targetsman 22 cal , which I bought right before they quit making them. Still have it and have no plans on getting rid of it any time in the future.
A Tanfoglio TA 90 in 9mm. Still have it and still shoot it-every once in awhile. Had to get new magazines because the poor thing was having feed issues and that situation might be remedied by stretching the springs out a little in the original magazines but we will see. Had much greater success with the second an M & P Colt in .38 Special. Also the first pistol I learned reloading with. Still have it as well and enjoy busting caps through it regularly.
I'd buy the same thing again. My first handgun was a Beretta 92F, I loved the way it looked and felt in my hand the first time I picked it up. Nothing has changed since I got it 25 years ago. Still have it, still love it!