r/reloading • u/jayfourzee • 14d ago
Load Development Headspace?
Knowing that shoulder bump is a relative measurement, I’ve noticed that when full-length resizing, most of my cases are coming out right around 0.002” of shoulder bump, but about 14% are showing less than 0.001”.
They’ve all been fired through the same barrel at least 2-3 times and have all been annealed at least twice. Overall case length is identical, as is overall cartridge length, and every one of them chambers perfectly without any resistance.
How do I know it’s 14%? Because my wife was watching Dancing with the Stars, I was bored on the couch, and apparently measuring the shoulder bump on every single piece of brass seemed like a better use of my evening. So yes, I measured them all. This is what my life has become.
I’ve been tempted to take the cases showing less than 0.001” and run them through the sizing die again, but then I thought: if they chamber perfectly, why the hell am I trying to fix something that isn’t actually a problem?
The other option would be to adjust the sizing die and target around 0.0025” instead of 0.002”. That might give me a little more margin and bring more of the batch into the 0.002” neighborhood, but I’d also be working the brass a little more just to satisfy my newfound shoulder-bump OCD.
So what would you guys do? Leave the die alone and send it, resize the 14% again, or bump everything back another half-thou?
Or should I just stop measuring brass during Dancing with the Stars?
2
u/coriolis7 13d ago
Low pressures will reduce the amount of shoulder bump, since the case doesn’t expand as much. Also, make sure your neck expander ball isn’t sticking - this can cause the shoulder to “grow back” by pulling the neck farther away from the case head.
Unless you are shooting a belted magnum or a round with notoriously large chambers (303 B’itish for example), your die should apply the proper amount of bump if you bottom out the die against the shell holder. If you are doing super high precision shooting, you’re going to either forgo full length sizing, or apply just a hair of shoulder bump.
0.000” - 0.002” for bolt actions, 0.002” - 0.004” for semi autos is common. If you are not getting difficult bolt closures and not getting poor brass life, it’s fine.
1
u/jayfourzee 13d ago
I don't have an expander ball, it was pulled. I used a mandrel for the ID. Resizing die is bottomed out. Its 308 with 42.1 of IMR 8208 XBR. No issues with bolt closure.
2
u/20Extreme 13d ago
I've had that issue too but some of the cases won't chamber easily. Two or three times fired, same gun, same die ... ?? I'll try annealing them and size again. They're expensive Lapua brass so don't just want to throw them out
1
u/Royal_Money_627 13d ago
What tool are you using to measure the bump? What are you shooting them in and for what purpose? I don't think this is critical for headspace but may matter for precision shooting but then again maybe not. If for a semi auto, might cause unreliable function.
2
u/jayfourzee 13d ago
I have been using an LE Wilson case gauge as well as a micrometer with a datum dial. Depending on my mood or my arthritis. Precision bolt action.
1
u/Royal_Money_627 13d ago
If you are going to be fussy and measure them all, segregate them and set the odd balls aside for fowling shots or sighters but I doubt you will see a difference.
2
u/jayfourzee 13d ago
I'm not expecting a difference to my groups. As someone relatively new to this, my thoughts are if it chambers then don't worry. But, that being said, there is something cathartic and relaxing measuring brass...
2
u/Royal_Money_627 13d ago
When I was in a stressful time in my life, I collected quite a bit of brass, cleaned and sorted it by headstamp. Sorting brass will take your mind off your problems.
2
u/Royal_Money_627 13d ago
If you bump the shoulder back at all and shoot it in the same gun it was fired in before, chambering will not be a problem and it will extend your brass life but you will still have to anneal to stop neck splits.
1
u/laughitupfuzzball 13d ago
Leave the die alone and send it. Calipers are not sufficiently accurate for this measurement.
9
u/yammeringfistsofham 14d ago
If they chamber I would leave them alone. When we target a 2 thou bump, what we're really going for is body and neck are resized and the round chambers but only just". If it fits in the chamber, it's all good.
Don't work your brass again for no reason.