I am about to retire (Woohoo). I shoot primarily long-range with (mostly) 6.5 Creedmoor and 300 WinMag, although I also occasionally shoot my .308, .224 Valkyrie, 6.5 Grendel, and when I want to beat the crap out of my shoulder ... a .338 Lapua. I've only shot factory ammo, mostly Hornady AG or ELDM, and have gotten solid results with good hit percentages out to a mile (so far). And like everyone else, I've got a safe full of 5.56 and 300-BLK AR's and various caliber pistols (which I rarely shoot).
My focus now is on long range shooting ... 1,000+ yards out to and beyond a mile, eventually getting into PRS competition form.
Primary long range rifles are a Barrett MRAD (barrels in 6.5, .308, .300, .338), MPA 300-WMBA (.300), Tikka T3x TAC A1 (6.5), and LWRCI REPR MKII (6.5).
I've only had time to shoot, not to reload, hence the factory ammo. That all changes soon.
Here's my question to experienced reloaders: Given that profile, and knowing what you know now ... what are the biggest MISTAKES you made when you first got into reloading?
Ok, first, you're WAY ahead of me in the hardware dept and the range you're shooting out to........kudos, you're an example to me.
Ever since Obama got me into shooting ten years ago and then the kids gave me a Hornady reloading kit, I've been a diligent student of reloading for precision shooting........starting with 270 Win before moving to RPR 6.5 CM and RPR 338 LM. I feel very confident of my reloading abilities, while ever seeking to improve them.
That said, the biggest mistake I made reloading? Getting into it solo, aka On The Job Training, with much time on you tube (a blessing) and forever acquiring equipment as I moved up in quality.......leaving so much equipment up on the shelves or under the tables. This might not matter as much to you, but I wasted for me a lot of money on stuff I soon left behind. I'd suggest trying to find someone who reloads who shoots similar to your capabilities and asking to learn from them enough to get started, whether you have to pay for it or what.
A few pieces of equipment I'd highly recommend: The Giraud case annealer and the Giraud case trimmer........Doug knows how to do it. The RCBS Chargemaster (?, old man's memory), cheap one is about $300, pricier one with two tricklers is about $900. I've only had the cheaper one and it does wonderful work. It has it's own trickler and scales. Some people like to have it go so far on a load, then use an independent trickler to top it off. The "Dandy Trickler" is a fantastic little two speed device that works great for this.
I use a Redding T-7 press, there are lots of presses. My original Hornady was great, if only one hole but with quick change inserts.
Dies are important, and precision match dies with sleeves are great to use.
Use good brass that will cycle well a few times before requiring annealing.......Hornady, Norma, Lapua and others.....
Make sure to use the right primers, don't substitute a Large Rifle for a Large Rifle Magnum primer and such.
Powders and bullets can be a little sketchy to find these days of Covid and record gun sales.......Usually you can use more than one powder for your desired bullet weight. Develop a suppliers list. Check with Midsouth if Midway doesn't have it. Etc.
For REAL precision, learn the discipline of keeping all brass segregated not only by manufacturer, but also by lot and by number of times fired.
I originally began reloading with the expectation it was going to save me some money. Soon I realized this was only true if I did not try to pay myself for my time. Now I reload because I feel much more confident with my own loads. One of these days I'm going to buy some good match ammo and take it out to compare to my own, see if I'm a good reloader or an illusionist. But I will admit I'm much more ready to go out and shoot 50-60 rounds when they've just cost me "supplies out of the closet" versus going and spending $30 per 20 round box!
Good luck, hope SOMETHING here helps out a bit. Have fun!