Printable View
Newbie question number....?
So was checking my brass pre cleaning and noticed this defined line around the bottom
Attachment 134841
Twice fired brass in my gun. I have only neck sized. I have been running them in the seating die a few times trying to get that exact OAL as I've found a lot of the projectiles arent the same length. Was hoping this might be it... Am going to prep a paper clip as per @grandpamac reloading tip
Charlie Horse, have a sneaking suspicion that line is the limit of the cold forging (pressing it into the correct shape) that your die exerts on the case.
To prove or disprove this I suggest you lube the case, put it back in the press, pull the handle all the way down and mark the part of the case you can still see with a marker of some kind.
Looks pretty normal, by all means check with the paper clip but id say your fine.
On your brass yes. Drop a reloaded round into the chamber and see how much protrudes, only rimmed cases are entirely within the chamber rimless ones always have something hanging out the back.
What you are probably seeing is the difference in surface finish caused by firing pushingles the case onto the chamber walls.
With your paper clip also measure the depth of the case and compare it to where the line is, it may be the web, wall junction mark as well.
Greetings,
Agree with the above. The shiny bit is where the case has expanded to be in contact with the chamber and the duller bit where the solid head of the case has not expanded. Pretty standard foe neck sized cases.
Regards Grandpamac.
Thanks guys, all things I'm learning along the way. Appreciate it
That's right about where one of my 243's gave me a head separation.
Lever action that always required trimming and lots of resizing, min chamber diameter I suspect.
I learnt to alway's check down inside the case with a pick. Any brass starting to catch the pick in the inside got turfed.
Often that was only 4-5 reloads and not max loaded either.
Z
I would suggest it was more likely a MAXIMUM chamber.....thus brass grew heaps each time it was fired...a minimum chamber would leave brass pretty much the right size....needing little work.Quote:
Originally Posted by ZQLewis
Yes this.Quote:
Originally Posted by Micky Duck
Grandpa Mac's explanation is the correct one.
The case wall thickness tapers from thin at the mouth to thick at the base.
When you fire it, most of the case expands, gripping the chamber wall. Near the base the wall is thicker and it doesn't expand. With as very hot load, the base will expand a little and not spring back. This is the case base expansion that people measure for when developing new loads. It's said this should be unmeasurable (<0.001") but I'm not sure what is really safe, myself.
Now, when you resize your case, the die squeezes the body back down to a smaller diameter so it will fit back into the chamber. Thus, over repeated firings it gets worked and flexed at this boundary of body expansion at each shot. That's why case heads usually separate just there, about 4mm in front of the base. You can test for damage by feeling on the inside of the case with as bent paper clip. Often you can see it as a bright line, a ring around the case, on the outside and it goes into a groove you can feel with your fingernail before it breaks.
If you've only neck sized the case so far, what you're seeing is the surface of the brass changing where its forced up against the chamber wall. The last 4mm to the base hasn't been in contact with the chamber.
So, it's 100% normal and no worries until you can see as thin bright ring around the case there.
Almost correct, what causes case head separation in that area is not actually anything to do with the die working the brass in that area....the die actually sizes very little near the case head.Quote:
Originally Posted by Bagheera
What actually causes case head separation in 90% of cases is excessive head space, that doesn't mean the rifle is large chambered or has excessive head space (tho the latter could contribute if the re loader is unaware of "headspace" )
When a cartridge is fired it is driven forward by the firing pin hitting the primer thus taking up any "slack" in the chamber/headspace.
Primer and powder ignite and pressure rises in the case, the thinnest "brass" of the case generally the neck expands and seals against the chamber first and grips the chamber.
As the pressure builds the case stretches out to the chamber walls and grips them untill the much thicker case web and base can no longer expand and are driven rearward until held in place by the bolt face....the gap from bolt face to brass is effective headspace and the brass will stretch that amount (generally with a few caveats) every firing and 99 percent of it in that case head/web junction.
So that is where all the stretch happens hence the separation, nothing to do with (correctly set) dies
Yes This Above.Quote:
Originally Posted by veitnamcam
So to summarise, if the case has been sized so that it is too short for the particular chamber when it stretches at firing there can be separation. Which means that the 'ideal' case length and sizing for a bolt action is when the case 'just' chambers with no excess play. So neck sizing and bumping the shoulder back just a little if you have to. Lever Actions more tricky to get right which is why lever hunters should only use Savage 99's
