Another head space question

.002 head clearance for your sized brass is a good thing.
Your bolt closing easily is a good thing.

Item 2,your bolt closes easily on 1.6255 brass. So,I'm skeptical of your 1.622 chamber estimate.

No need to go shorter than 1.6235. That's .002 clearance on 1.6255 brass that chambers easily.

You said 1.6275 was hard to chamber. You would maybe allow at least .001 for the "hard" interference,and add .002 for head clearance.That says a max of 1.6245 to me.My .001 allowance for interference is based on allowing "something" without knowing how much..002 might be better. I just don't know,but IMO,you have narrowed the window to 1.6235 to 1.6245.This is allowing .002 head clearance for reliability.
Write that number down in your die box with a sharpie. If you have a feeler gauge that will set your die to give that length,note that,too. Seems like .001 or .0015. That's available as shim stock. A cigarette paper is about .001 (ZigZag)

Note:Post 1 you said sized brass was 1.605 for .017 head clearance? What happened?Might have to do with clamping all the Hornady pieces together.
 
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Action closes on group 2 (max. 1.626”) with no resistance.

Action cannot close on group 3 (min. 1.628").

So the rifle's headspace should be somewhere between 1.626” and 1.628”. I would size to 1.625” to 1.626”.

It is pretty simple really.

-TL

Sent from my SM-G930T using Tapatalk
 
303s I have seen have all kinds of air space below the shoulder of the chamber and shoulder of the case.

I also have a min dimension chamber reamer and I quit chambering just as soon as the rim touches the back of the barrel so I am changing it to locate on the shoulder. That way when I size I only bump the shoulder back about .002".

The base of the body expansion is also excessive on factory chambers. My reamer cuts a chamber .002 larger than a unfired round.

Before I had this made I backed up my FL die for plenty of clearance before it contacts shell holder and theoretically headspaces on the shoulder.

I have a 30-30 that has the same problem but also has excessive headspace to the point I was having light strikes/failure to fire so I had to back off the die as above and control the shoulder location.

I made a poor man's case gage by using a section of 30 cal barrel and running a finish reamer in till just past the shoulder. The whole thing is only about 3/4" long and I measure from head of case to head of gage with calipers and set FL dies to just bump back shoulder .002".

I have come to the conclusion and came up with the 222 rule which means I don't want any part of the case expanding or moving over .002" on firing.
 
Yosemite Steve said:
What happens if we make the cartridge fit the chamber with zero headspace?
Click to expand...
That's basically a philosophical question. Some people who are very good at this sort of things studied it, and they determine 0.002" is the best compromise for everything.

I buy that. At least it makes the bolt move smoothly. The sizing operation is not exact. It easily can have tolerance as much as +/- 0.002". Without bumping the shoulder by that much, some of the rounds will going in with resistance. They are being squeezed in the chamber, while the rest are free resting in the chamber. Apparently this introduces more variations.

-TL

Sent from my SM-G930T using Tapatalk
 
"What happens if we make the cartridge fit the chamber with zero headspace?"

Under perfect conditions, that's great.
That's why hunting ammo often is allowed more slop than range use ammo.
 
I'd like to chime in . Ruger bolt action for target or hunting? Target .002 hunting .003 All Chambers are different , cases can stretch an also expand . My fired cases would get shorter from expansion. Having a longer case is easier to get the right case length. I would size the longer case down to where it has alittle resistance , that's zero case head space from bolt face to datum , then at that point you can go .001 with no resistance to what ever bump you want . Keep that zero measurement no matter what it is. Zero headspace isn't good for you bolt locking lugs , you don't want to gall the lugs. The average 308 chamber is 1.630 , get a go Gage to check your chamber , you can add shim stock to find your chamber length. Hope I helped .

Chris
 
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