Also a new reloader (still getting things together before I start) and would love to chuck a couple of questions into the mix.
- How important is case trimming for a double rifle (9.3x74r)?
- Is a Lee autodisk powder dispenser 'good enough' or do I need to measure the charges on a scale as well?
Case trimming is vitally important for safety. Yes, you have some leeway with bullet seating depth, but you do not with case length. Chamber a case that is too long and it can lead to excessive pressure or failure to extract. I avoided reloading for decades because I ignorantly feared the case trimming process. Trimming is just another measurement and action; still the least enjoyable part of reloading, but I've come to enjoy it more now that I have a good trimmer. Case length is important for all rifle cartridges.
No dispenser is 'good enough' on its own without some way to verify the charge it's throwing. EVERY responsible reloader needs an accurate scale to verify the charges that are thrown. Most reloaders who rely on a dispenser to throw an accurate charge still weigh every 3rd or 5th or 10th throw just to make sure nothing has changed. Speaking for myself, I weigh EVERY charge on TWO scales; a balance beam and an electronic.
I see someone already listed a RCBS link that details the steps for reloading. It really isn't rocket science as I'm sure you've figured out by now. That link does a good job of explaining it.
But, at the risk of being labeled "that guy on the internet giving questionable advice", I do take issue with one of the steps that RCBS details. This step is where you set your resizing die. RCBS says to screw the die down until you hit the shell plate with the ram in the full upward position. Then lower the ram and screw the die down 1/8 to 1/4 of a turn.
That may work fine for some rifles, but definitely not others. For some rifles that is excessively resizing, bumping the shoulder of the case back to far. This results in excessive case stretch upon further firing. Case head separation can and does occur. It happened to me.
My gunsmith said that I was likely oversizing. I did a little more research and basically ended up in most cases just turning the die in further by just a smidge. Just enough to kiss that shoulder back in about 0.002". This ensures the case will fit, but limits the stretch that occurs on next firing.
This leads to longer case life and hopefully not a full case head separation once you get to end of case life.
This is good advice, but maybe not for the beginning reloader. It's best to follow the die manufacturer's instructions at the beginning and then experiment with shoulder setback as experience grows. The die manufacturers write their instructions so that sized cases are at SAAMI spec, which guarantees feeding and extraction without excessive pressure. Matching shoulder bump to the chamber is a detail that can be worked on as the new reloader gains experience. NOT chasing the lands, NOT neck sizing only, and NOT just bumping the shoulder is good advice for the beginner. Follow the manufacturer's instructions when getting started.
I would argue that anytime a case is longer than SAAMI spec, you should trim regardless of caliber.
I'm not familiar with the powder dispenser you mentioned, but for me, I want every charge weighed and to see what it's at. At least when it comes to rifles. I load for accuracy which means consistency.
What is typical of MOST reloading manuals is to trim to 10/1,000 (ten thousandths) below SAAMI maximum. Some manuals have this at 5/1,000. Again, no matter what powder dispenser you choose, you can't trust it without some accurate way of measuring the charge. This is a pet peeve of mine (probably no one else's): DO NOT believe/trust the oldtimers or newtimers who say that powder is dispensed by volume and leave it at that. That statement is ignorance of what a grain is - it's a measure of MASS, which is a weight. It is true that a volume can be calibrated to deliver a certain mass depending on the density of the powder, but there are so many powders that there is no fixed density that allows volume to be the sole arbiter of powder charge. Even published and revered experts make this mistake. (Okay, I'm ranting; get a trustworthy scale to verify your powder charges)
If you use a balance scale, keep all plastic bags away from it--they mess with something and you do not get a consistent charge. Something about static electricity ? Just move them out of reach while using it. Powder dispensers are probably fine. Jim Carmicheal wrote that some of his best groups were with thrown charges. Other things matter more. Small mistakes add up together.
Nothing wrong with thrown charges as long as they are first verified by weight and then checked periodically.