Headspace calculations??????

[oua660]

:? Hi brand new to forum.... Been reloading for a little while and LOVE it. BUT started in on head spacing and I'm confused. I took an empty sized brass and cut a section out of the neck then resized and placed the chosen bullet in by hand. I then ran it through the gun It is intended for five times and averaged the results. The average was .232 OVER C.O.A.L. so even if I knock it back .015-.030 of an inch It is still past Overall length. So do I just seat to max? I'm looking for better groups and was informed this is the way.

Thank you Josh

 

[RiverRider]

Josh, welcome to the forum. It's really a great place!

You're talking about seating depth here. Headspace is a different animal that relates to how well the case itself fits the chamber and it has nothing to do with the bullet or OAL.

So. There is no limit to how long your finished cartridge can be other than the fact you do not want to be jamming the bullet into the lands AND you may end up with finished cartridges that are too long for the magazine.

What you have done here is you have found where the bullet just engages the lands. You'll probably want to seat seat the bullets to be anywhere from .010" to .100" or even more from the lands. I have found that many bullets work well at about .030" from the lands and others work well at about .015" from the lands. If your magazine dictates more distance from the lands, don't sweat it. There can be more than one sweet spot.

I would strongly suggest using a comparator to make all these measurements. Tiny differences in even polycarbonate tips can create confusing inconsistencies. There was a time I refused to use a comparator because I figured that if I made the initial measurement to the lands going off the cartridge OAL, and I used that same bullet to set the seater die up I should be golden. I gave in and started using a comparator and I now use it for ALL rifle bullet seating measurements. It just yields more consistent and repeatable results IMO.

 

[nvbroncrider]

Josh,

By what you are saying I'm understanding that you want something different. Headspace is the distance the cartridge travels when fired before it reaches the chamber walls. Too tight of a chamber ie too little head space you won't be able to close the bolt. Too much headspace and you will see high pressure on very light loads and possibly rupture cases near the web.

Now what I think your trying to determine is the throat of your rifle or distance to the lands. now for this you are measuring correctly. The way I do it is take a fired case and slightly push in the neck againest the corner of my bench that way I can press a bullet by hand into the case and the neck holds it. Next I seat the bullet by hand farther out than normal and take a sharpie and color the bullet. Then when you chamber the round if it is too long it will press the bullet deeper into the case. You will see the point of contact with the lands as rifling on the bullet. After doing this and measuring your round you can now determind where your lands are generally for best accuracy about .010" off the lands is recommended. Some bullets like the AccuBond and E-tip will need more jump. Now your rifle may be throated a little longer than SAMMI COAL. Don't worry about that since you are measuring it. It happens in some rifles from the factory. My custom .280AI is throated at 3.45" and SAMMI is 3.34" I did this to gain powder capacity and performance.

What are you loading and shooting? I'm sure others will be on to point you in the right direction on your particular cartridge.

Jake

 

[oua660]

Hey yeah, sorry Bullet seating Off the lands. LOL always been iffy when I talk about that for some reason headspace jumps in my head. ok thanks for the help so far....