Head size? 6PPC

Vern

Vern

Morethan1waytoskinacat
Not sure about the title but anyway. I fire formed some cases on Friday. I didnt think to check them for size then but now I checks my last cases from last year and I measured the case right at the extractor groove.
Last years cases fresh fired unsized and after resizing were .4420 (the same).
The cases I fireformed Friday are only .4385 at the same spot.
I dont think I have ever thought to measure cases there at this point but it doesnt seem right that there would be that much difference or that cases should expand that much more there.
I realize that the .220 brass is supposed to be .443 but why do my news ones seem to be undersized.
It is the same barrel and chamber as last year. Have the production sizes changed?
 
As a secondary followup:
Most (not all) trim to around 1.490.
I have done this in the past prior to turning.
However almost all the cases are around 1.485 +-.
Out of 2 handfuls only 2 were at 1.490+

Shorter than normal and narrower than normal.
Whats up with this?
 
You did not mention any specifics as to Brand Name or lot number. The newest Lapua .220 Russion I have measures about .439 right above the extractor groove and about 1.515 overall length. I use a long enough chamber that I do not need to trim before fire forming and they shorten up to about 1.495. I don't trim until they reach 1.515 again.
I found a few older unfired cases that measure about 1.441 above the extractor groove. I have not looked at any of the new "blue box".
 
As an afterthought, I dug out my oldest retired cases from at least 3 years ago and measured the body diameter in front of the extractor groove. They all measured very close to .440.
My reamer prints specify .440 at .200 in front of the bolt face. If new brass was .443 in front of the extractor groove, I would not be able to chamber them.

Scott
 
Lapua, I just got them from Sinclair a couple of weeks ago so a newer lot.
I dont know the width of the chamber at that point but I will be casting it in a few days or next weekend depending on time.
The length of the chamber is suppose to be 1.500.
Thanks for the info.
 
Facts I found yesterday

Ok here are some FACTS that I found last night.
I am prepping some 220 Lapua brass. Oddly enough the box I received last month is the exact same lot as the one I got January last year. Lot P00406602, both from Sinclair.
Here is what I found about the primer pockets and holes.
Last year I bought a K&M primer pocket uniformer/reamer. It never quite seemed to clean up the pockets around the flash hole.
I have fireformed the cases last night I started to uniforming the primer pockets and noticed the same thing around the flash hole, a small roundish area that just didnt come clean and retained some to of the carbon.

Primer Pockets
I took a case and reset the uniformer to clean all of the carbon. About 2 cases later I had the same thing then again. A case that would not clean up right around the hole then a few more cases the same thing. I reset the uniformer for .0015 deeper using a feeler guage and started over most cleaned up but a couple didnt. Out of 30 cases I did 7 did not clean up completely which shows the primer pockets are not uniform.
Further some of the pockets had a lot of brass that came out of them and those 7 had very little. Some were actually so shallow that I really had to hang on to the case holder to keep it from coming out of my hand and there was a lot of difference in the amount of brass particles that came from various holes.

Flash holes.
When you examine them outside and inside the appear to be punched. they are concave on the outside in the pocket area and they are convex (raised) on the inside of the case.
Flash holes some were larger than others and some were slightly off round.
I used a K&M flash hole uniformer and out of the same 30 cases 6 holes were so small I really had to do a lot of twisting to get the reamer through the hole.
Looking at the brass on the table top under the holes some were worse than others.
These 6 were some that didnt clean up completely and some were from the ones that were completely clean.

Conclusion the primer pockets and the holes are not very uniform and in this lot they are punched and not drilled.
 
As a follow up.
I have done about 93 cases. 21 of the cases still have some sort of deficiency, uncut area right around the flash hole. There for 21+% at this point are not uniform.
I know we tend to throw away brass that does not measure up BUT Ill be danged if Ill accept a 21+% loss. When I pay almost $100 for a box of brass if I have to throw away almost 1/4 or 25% there is something wrong with that.
I am thinking about extending the cutter another 1/2 thou or so to get them to all clean up the same. Might be a little more or a little less. I dont know till I try it.
What do you think.??????????
 
I would fire the brass one more time before cleaning up the primer pockets. I would also assume that you had the same charge in all cases and that the round was seated into lans.
 
You must log in or register to reply here.
Back
Top