Thread: Headspace gauge/ case head separation

Greetings all,
I struggled with setting headspace on my brass for decades. For years I neck sized brass, which brought its own set of problems, and meddled with setting the die of the shell holder with a feeler gauge. Nothing, I repeat nothing is half as convenient or accurate as using the Hornady headspace comparator together with the Redding Competition shell holder set to achieve consistent headspace on my sized brass.
Regards Grandpamac.

Originally Posted by grandpamac

Greetings all,
I struggled with setting headspace on my brass for decades. For years I neck sized brass, which brought its own set of problems, and meddled with setting the die of the shell holder with a feeler gauge. Nothing, I repeat nothing is half as convenient or accurate as using the Hornady headspace comparator together with the Redding Competition shell holder set to achieve consistent headspace on my sized brass.
Regards Grandpamac.

Yep redding comp shell holders are absolutely fantastic
The other way to do it is find a tight ish bit of fired brass and take the decapping rod out of your die.
Start sizing with the 10.000 holder and work down 2.000 at a time till you have bolt closing tension you require.
Alot of my cases of diferenf chambers sit at 6.000 which means if I didn't use them I would have between 6.000 to 7.000 head space which for me fixed case head separation I was having problems with.
For those of you who just undo their die a fraction at a time it has been proven to be quite an inaccurate way to gain exact replication of head space.
A redding podcast explained why it is so!

Sent from my SM-A556E using Tapatalk

It's a funny old thing, years back we were taught to never wind the die in hard and lock it solid as that way it can float and not push the case of too one side with an affect on the neck runout. If only we knew how bad it was for headspace!!!

This is how I do it now.
IMO for hunters anything from 0.002" to 0.005" would be fine as you tend to lose cases in the field.
The tape is a good trick.
To measure bump u can get away with a pistol case.
I just use a short length of brass with a hole drilled down the centre to give u a "tube" of brass. It's about 20mm in diameter. I have two. One for 223 and another 30.06. The hole in the brass sits about halfway down the shoulder. Just sit over the nech/shoulder and use dial caliper to measure.

Having said that I'm sure the Hornady comparator would be better and more consistant. I don't neck size any more.

https://youtu.be/htvk1UYOXm8?si=UlPxVmkwpUJeWBT5

Originally Posted by No.3

It's a funny old thing, years back we were taught to never wind the die in hard and lock it solid as that way it can float and not push the case of too one side with an affect on the neck runout. If only we knew how bad it was for headspace!!!

Greetings @No.3 and all,
There were a lot of things touted as fact that many find hilarious these days. Regrettably many can not let go old beliefs that were debunked decades back. We each develop our craft of handloading in different ways and at different speeds. It is well over 50 years since I timidly put my first handload together. A .303 with a 180 grain Norma projectile and 34 grains of AR2201 powder. Decades later I am loading 150 grain Hornady projectiles in my .303 in neck sized cases with a light 34 grain load of AR2206H for around 2,100 fps. Some things change but others not so much.
GPM.

Originally Posted by Porter83

I'll have a search to see if I can find the diagram on how many thou each fraction of a turn does.

80 thou per full turn on my dies.

No one has mentioned yet that new brass can take 2 or 3 firings before it stretches out enough that the shoulder contacts the chamber and causes tight bolt closing. So you think you ve got good clearance and done enough sizing but you need to rethink a few months later .

Has anyone else found this or just me ?

Ive actually noticed that but thought everyone would know that...

The distance from the cartridge base to a defined reference point on the shoulder is called the cartridge headspace dimension, to distinguish it from the chamber headspace dimension, which is fixed when the chamber is reamed out, as long as the bolt lugs dont wear down. This is shown on the SAAMI drawings which you can find by google.




For 223 the specified headspace dimension, shown on the drawing below with a triangle snd an asterix, are actually at the corners at front and back of the shoulder. But SAAMI also helpfully specify a length in the middle of the shoulder at a diameter of 0.330” where it is easy to measure. Ive indicated the length at 0.330 with fine red arrows. The required cartridge headspace length is 1.4666” down to 1.4596” @0.330”. Hornady helpfully make a set of gauges which includes one with 0.330” internal diameter.

This is the setup you need:



This is a Federal factory loaded round and the length is 1.4555” or maybe 4 thou shorter than SAAMI spec. However, the gauge seems to have a small chamfer on the inside to enable smooth seating and twiddling without scratching the brass, so perhaps it under measures the length at 0.330. As noted in an earlier post, the gauge is for comparing cartridges rather than getting an absolute length to compare with your chamber.

Ideally, you will see each case shortened in this dimension by around 0.003” when its sized.

I'd suggest the OP search YT for Eric Cortina's item on setting FL dies.

Basically, you first dismantle the bolt and remove the striker assembly so the bolt will fall closed on its own if there is nothing in the chamber. Start with the die set long ( ie, no sizing other that neck) and slowly wind it down in say 1/16 turns until you reach a point where the bolt will -just- fall closed with the case in there. This will be minimum shoulder clearance and should eliminate the case separations.

Using this technique in my main target gun, the resultant shoulder bump was 1.5 thou measured with a gauge made from a case fired in that chamber.