Headspace is not brass body

[Barzor]

Finally figured it out. I was wondering why my bolt was hard to close after 3 firings and neck only die. I thought that bullet was too far out but it wasn’t. Also the headspace gauge/ Rcbs precision mic read 3 lines before zero. Meaning headspace is a touch smaller than spec. So why was it still hard to close.

So I took the plunger and firing pin off my bolt to see if after doing all my prep and neck sizing if it still did this. And yes it does not close easily. I decided to use my fl die with out the decapper and ball as I already use the lee collet neck die.

I put lube then put through die then cleaned and tried in rifle and this time it closed easily. I checked the Rcbs mic again and once again the measurement as on the same spot. It did not move. It seems the reason it was difficult to close bolt was because the body had gotten larger and once in fl die it shrank it to proper specs.

I had thought that measuring headspace also measured the body of the case. Shouldn’t the headspace grow taller if the body is pushed in??

I am really having hard time setting up my fl die and is why I gravitated to the neck die. When I use the fl die I notice that at times the head space measure ment is not always the same. Sometimes i have to screw in the fl die and make adjustments so that the headspace is smaller. When we fire the rifle the case conforms to the chamber. The chamber does not get larger or shrink. Why is the fl die not consistent. I make sure I have same amount of lube and same pressure on the press. But sometimes I notice there are cases that is hard to press and some are easier.

Basically I have to measure headspace of each case every time out of the fl die only when I feel a different resistant on the press.

Is this all normal. When I buy a box of Lapua brass and once fire the case and put through my fl die each brass may stretch differently I may have to measure each and adjust die each time.

 

[FLIGHT762]

As you found, you cannot neck only size only forever. At some point, you need to F/L size. I found this out decades ago and if I want to N/O size, I will not go over three N/O reloadings. I use a Lee Collet die along with a Redding Body Die and get very accurate ammo with low runout.

As far as inconsistent shoulder bump, it can be caused by inconsistent case lube and from case work hardening. Annealing can help, but freshly annealed cases will give more shoulder bump from your initial die setting. This is why some of use use the Redding Competition shell holders to adjust shoulder bump without having to reset the F/L die. Different brands of brass will bump differently.

I have found dwell time can sometimes help. Instead of running the case in and out the F/L die really fast, you run it into the die slower and let it dwell for a couple of seconds in the die before lowering the ram. I have seen you tube videos of testing dwell time and some have found no difference, but it is worth a try to see.

 

[Maurygold]

I prefer to run the die into the shellholder and use redding comset (or 419 or the zero) to control headspace

Redding Competition Shell Holder Set #7 (45 Winchester Mag)

The Redding Competition Shellholder Kit consists of five shellholders in varying heights with increments of .002". Allows you to increase or...

www.midwayusa.com

 

[spife7980]

Headspace is not the body of the case, correct. Headspace is the distance from the bolt face to a certain point in the chamber. When you fire the case, it blows the shoulder forward to fill any empty headspace clearances between the brass and the chamber.

But it doesnt only grow in the one direction, it also grows out round and gets fatter which is often what you feel in the bolt resistance when chambering and extracting.

Full Length sizing die sizes down the base diameter, shoulder diameter, shoulder set back and neck diameter.
Body die sizes down the base diameter, shoulder diameter, shoulder set back
Neck die sizes down the neck

How deep you screw in the body or full length die into the press controls how much it sets the shoulder back, the deeper you screw it down, the shorter the space allowed for the shoulder to exist before it gets pushed back.

How the shoulder reacts depends. If its been several times fired and has gotten progressively work hardened, you may find that it springs back variable amounts. If you have nice new or freshly annealed cases then the shoulder should pretty much stay where you size it to.
If you find that the shoulder datum dimension gets longer, your die isnt screwed down far enough and its the squeezing of the body diameters thats shoving the shoulder forward until the die gets lowered enough to rebend where the shoulder is.

In short:
Your die diameters are pretty much what they are as set by the die and eventually need to be squeezed down after firing.
How far you screw the die itself in controls how much headspace clearance you make between the case shoulder and the chamber shoulder.

 

[memilanuk]

Lots of good info above; one thing I'd like to add: don't try to size a case (or cases) repeatedly. The results will be, at best, misleading. Partially sized cases don't respond the same as fired, unsized cases and will skew your measurements.

Take a fired, cleaned, lubed case, size it and measure. Set it aside, whatever you have to do to make sure you don't pick it up again inadvertently. Adjust the die, shell holder, whatever, and grab a 'fresh' fired, cleaned, lubed case and size / measure it. Repeat as needed.

Once you get the die set where you want it, lock it down. *Then* grab the test cases, and run them through again. Load em up for foulers, sighters, positional practice, whatever. Just maybe don't use them for load testing or other 'precision' shooting until they've been fired again.