OK, since you've asked several questions, and in an attempt to make it a little easier to follow the answers, I'll answer each one inside your post.
Thank you for your input. The first time I started collecting brass not too long ago, I was picking up whatever I could get my hands at. One time I even started chatting with the fellow in the lane next time mine, and when I found out he didn't collect his brass, asked him if I could have his! While that may work for many, after much reading, I heeded to one of the things you warned about, of not knowing how many times a particular brass has been fired. Being so new, the more I read, the more I started worrying about the what if's. Now I collect what comes out of mine, and even then, I'm inspecting each brass before they go under the knife, so to speak!
A very wise decision, at least for the time being. Always, always be sure to closely inspect each and every case you intend to load. And a very important issue to keep in mind is how much better you can inspect if all your brass is spotlessly clean. You can tumble them dry, or wet, or use ultrasonic cleaning ….. the method is secondary to the final product. But clean brass (not necessarily shiny, just clean) is far easier to inspect than when it's dirty, corroded, etc. And here's a tip … if you dry tumble them with walnut shell or other hard buffers, always (ALWAYS) check to be sure the primer pocket/hole is not blocked with a piece of shell. And keeping track of the # of times reloaded is just as important. You can sometimes go a few loadings before needing to 'full length' resize if you're loading them for the same firearm they were first fired in. But if they're being loaded for use in another firearm, always 'full length' resize. It may not always be totally necessary, but it is always prudent.
While I probably have almost 1500 reloads under my belt now (plus still have all my fingers), I still consider myself a novice. I do check OAL, but can't say I do the same with checking case length on 9mm, though I'm always checking on 223 after trimming/chamfering/deburring. I'm sneaking a little forum time at work so don't have my note/cheat sheet, but I have come across a few brass considerably shorter than others. Which brings me to my question about seating depth, and you may have indirectly already answered it above, but I'll ask anyway. If my brass is too long, wouldn't seating the bullet deeper still give the same OAL necessary? Or are we now taking the chance of added pressure due to the bullet seating too deep?
A couple real important issues here ….. “OAL” is a critical measurement in all cases. And even more important in the 9mm case than the .223 case. Remember the 9mm headspaces on the case mouth, the.223 headspeces on the case shoulder. Maybe I shouldn't say 'more important', but it is everybit AS important. Most 'too long' cartridges will do one of two things, both potentially dangerous. One – if it's too long due to not having seated the bullet deep enough, some guns will actually seat the bullet deeper when it goes to battery. Especially bolt actions, some pump actions, and on rare occasions even a good strong auto-loader. But, when that happens you may, depending on the load data you're using may find yourself with a 'compressed' charge. That is where the powder charge has been squeezed down tight inside the case due to the base of bullet compacting it. There are cases where that's desirable, but in your case I would strongly advise against it. Sometimes the action on a semi-auto won't have enough 'ummmph' to close on a 'too long' cartridge, in which case you've spent a lot of time loading and now will have to pull each bullet and start all over. But even more important is when the cartridge headspaces on the case mouth, like the 9mm. If the case itself is too long, the action almost assuredly won't close. So I would for now encourage you to ensure the case Max. Length is according to SAAMI specs. Takes a tad longer to trim them to length, but the possible alternative can be catastrophic. If a too long case is forced into a chamber, it could squeeze the case mouth into the chamber throat and the result is almost (or can be) the same as a plugged bbl. More likely in rifles and other shouldered cases than a straight case like the 9mm, but can happen. Remember the 9mm headspaces on the case mouth so it's really critical just how long that case is, both before and after crimping. Somewhere in your loading manual, I'm sure there will be a section on SAAMI specs for various calibers. Pay attention to all the measurements, not JUST the OAL. The case length is every bit as important, maybe more so than the OAL. Yes, seating a bullet deeper in a too long case will get you to the OAL, but in a potentially very dangerous way. You answered that question yourself with this quote “Or are we now taking the chance of added pressure due to the bullet seating too deep?” See, you're learning more than you thought.
Now for just a bit of an eye opener ….. You mentioned you now have 1500 loads under your belt and that you still have your fingers. That's a fair number for now but at some point you might see just how few that really is to where you will eventually get. An example is that back in the late 70's-80's and 90's, my wife and I shot an awful lot of competition around the SE. I would typically load >15 thousand (yeh, that's more than fifteen thousand) rounds per year just for our competitions. That didn't even include my and her plinking and hunting loads. Now you may never have a need to load that number, but try to make each and every load you do as perfect as you can make it.
One other hiccup I've run into that I thought I'd ask about is reloading 147gr. Up until recently, I've used Speer 115gr RN, Berry's 124gr Copper RN, and SNS 115gr RN with no issues. I happened to get my hands on some BlackBullets 147gr FN, and am having the most inconsistent seating depths on this group. Based on my initial testing, 1.130 OAL worked really good with the load I was using. I'll have 6-8 seat perfectly, then the next few will drop to 1.123ish. Then I'll have some go the opposite direction to 1.145. I measured a few brass to make sure I had the same length on them, but even then there was no consistency in my OAL. Could it be due to brass not resized to full length consistently? Variance in diameter of the bullet? The most logical explanation I've been able to find so far has to do with the ogive, but I wasn't fully convinced, so your thoughts would be much appreciated.
Let me start here with this one …. 1st a 147gr .355 dia bullet will be longer than either of the others you mentioned and will require you readjust your bullet seating die. The ogive may be affecting you, but if that were the case the variations should be pretty much consistent. Take a clean, empty case, no primer, and full length resized to use as your 'set-up'. Put a bullet in it and adjust/readjust your seating die until you get exactly the OAL you want (rely on SAAMI until you gain a little more experience). You may have to pull that bullet several times to get to the adjustment you want. And everytime you pull it, run that case back through the sizing die before you reseat the bullet. Why? Because the sizing die makes the case mouth just couple thousandths smaller than the actual bullet and each time the bullet goes in, it tends to stretch the case mouth out those couple thousandths leaving you a too loose seat to get a good setting on your seating die on your next adjustment. Now all this relies on your having been critical of all your die settings through the entire process. Sizer dies are important to get the overall size you're looking for especially concerning the case mouth. Also recognize that when you run a case through a full length sizing die, that very process will make that case a tad longer than when you started, just the same as shooting that case will also make it a tad longer than when you loaded it. The variation in some of your OAL's, leads me to believe you might not be checking the case length on all of them. If there's a difference in length of cases, or a difference in how the case was resized, or a number of other variations that you control, you will see variations in OAL. And I promise you these differences will make a difference in how they shoot, sometimes even how safe they are. I can't stress just how important it is to replicate the settings of each of your dies each time you sit down for a loading session. 'Replicating' what you're doing is the key to 'duplicating' your results.
I'll have to continue in the next post .....................................