I'm doing a new one in a few days.
Will be .243, 105 Targex with N560 in Lapua brass and Fed 210 match primers.
I will take 20 cases. Pity these cases. I want fired brass to work with, as fired vs unfired is pretty different sometimes I have found. I full length size everything.
I will rummage around on the internet and find a starting load. If I can not find one, I typically graph a bunch of other cases, look at bore to capacity ratios etc, similar weights and see where the case and projectile I have chosen would fall on the line. Also I will look at how much lighter a starting load typically is for that type of powder. Or I will get the gimp to make me one in Quickload.
I only want a genuine starting load. If you go too low you get gas back round the case or the mysterious low load blow up (real thing?).
I don't speak "thou" so for a long time I seated everything 1mm off the lands. Thats where my 6.5x47Lapua is sitting, and it shoots pretty spectacularly. It is however 40 thou off the lands and it upsets the Gimp when he sees it on the wall in my loading room, so this time I may go .5mm as that seems more the done thing (20 thousands of an inch).
I will load two rounds at 1.5g increments from the starting load and shoot them over the chrony. Im not seriously interested in starting loads, but I also do not want to discover the hard way I have one of those weird rifles that gives scary pressure signs at a starting load. Pressure signs or excessive velocity at this point and its going to the Smith.
I once the velocity gets into the vicinity of where it "should" be, probably 2x 2 shot groups, I will switch to 3 shot groups and .5g increments. I will start looking for pressure signs. All the fuss about STRAIN gauges.
Strain means
deformed. Elastic strain is when it springs back to its original shape. This is what a strain gauge measures, and it assumes you know your metal properties, and their elasticity very very well. If you do, then you can convert the amount of stretch to a pounds per square inch (PSI) number. As in how much pressure would it take to stretch the action X much. If you do not know them perfectly, the number is non-sense.
Permanent strain is when the item is permanently changed. This is what happens to your brass case. It gets deformed/strained and it stays in its new shape. You will hear people say that using "traditional" methods for identifying pressure signs is not quantitative and your will see things written like "you are just guessing". This shows a very poor understanding of what stress and strain actually do. A fancy strain gauge measures elastic strain of about one one millionth of a bees dick, in a tiny fraction of an instant. And it assumes you know the metal properties. Get that wrong and its nonsense, but how do you know its wrong?
Probably look at the cases. A case is a perfectly respectable, quantitative strain gauge. Its as quantitative as the fancy stick on PSI one, it just wont give you a number. Your measuring relative, permanent strain. Which is ideal, because that is all you wanted to know anyway. A blown up action is a permanently strained action. So is a wrecked case. PSI numbers, by comparison tell you very very little.
I measure the basses, and I load in 3 or 5 shot increments and come back to my shed and knock the primers out to check the primer pockets. Im a bit spoilt as my loading room is by my range and I can leave the rifle to cool right down while I load rounds and take all day. I polish the case base up and look hard for an ejector mark. I want to see no signs that I am permanently deforming the case base. To be honest in the past, I was more willing to abuse a case, but now I want them to last, and I care less about velocity. If I can find no signs of the case suffering but the primers are struggling I might switch to a harder primer (probably only relevant to the x47 and the small primered 08 case). Obviously sticky bolt lift is bad news. I would suggest (this is purely conjecture on my behalf but makes sense to me) that serious sticky bolt lift is the action/chamber starting to stretch excessively. It will stretch and expand slightly and spring back, the case definitely will not. So the chamber expands temporarily, then clamps down on the permanently deformed case, which expanded to fill the expanded chamber. You don't want to be regularly deforming your chamber, as this
could lead to metal fatigue and BOOM. Plus its super annoying, especially if you have a remington, as you will have to take your rifle and stuck case to the smith in one hand and your bolt handle in the other.
You brass is the weak link. As long as you are not permanently straining it, you will not be hurting anything else. Arguably, if your beating it up a bit with no sticky bolt lift, then you may be safe enough, I certainly know some people who are still alive who are constantly looking for stronger extractors and can count their firings from the number of ejector marks. I'm happy enough just getting a bigger gun or twisting the elevation turret a bit further.
I log velocity the whole way, and look for where the gains in velocity per grain start to plateau. I still want to go as fast as I can without wrecking the case. Lucky for me almost everything I have loaded for has tightened up around here somewhere. Once I have a clear front runner from the three shot groups, I will load a few at that weight and .2g either side in 5 shot groups, look at the velocity spread and see if it tightens up. If it just does not look like its going that well, with velocity or group size, I will just start over with a different powder at this point before I mess with seating depth.
Once I have a load I will load some more and do some dot shooting. Depending on how hot I went my 20 cases are probably looking pretty sad by now. I will keep them and use them as fouling rounds after a clean or lose them into circulation with the other cases where they can cause fliers for the next 2000 firings of my hundred cases.
Attachment 9026
Then I go out and cold shoot a single round semi regularly and log what happens.
Then I find some other problem and spend 6 months trying to figure out how to fix it.
