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Headspace??? Fired Cases shorter than than unfired cartridges.

MMH

I am beginning to reload for a Compass Lake AR15 that I have. This rifle has a Bartlein barrel & a CLE chamber. I was checking the headspace dimensions of cases fired from that rifle and am confused with what I am seeing. Using a Hornady headspace comparator w/ the A330 bushing, the fired cases are 1.456" long and unfired cartridges are 1.458" long. How could new, unfired cartridges have a measured headspace that is longer than the fired cases?

How should I set up the FL die? I wanted to set the shoulder back a minimal amount (0.003").
 
Case body expands outward on firing, pulling the shoulder back with lite to midrange loadings.

Set the fl die with a gap of .005" between the shell holder and fl die on a single stage press. See if sized brass will chamber. More adjustment may be needed next sizing as the brass grows with a few firings.

If using a Dillon progressive press, the shell plate may give a different shoulder bump at each station.
 
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Common misconception that brass will reach its maximum stretched case dimension on its first firing. It can happen but some times it does not and can really confuse folks. Some times it can take 3 or 4 fireings before a case will not chamber, if your not running a hot load. Semi Auto makes it tough to confirm vs a boltgun by inserting a fired case and closing the bolt.

Setting your sizing die off of new brass can at times create a lot of extra headspace ( more than .003) and there for cause brass to stretch and fail prematurely had the die been set with closer headspace.
Something to consider anyway. Hope all is well.
 
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All my max load fired cases are shorter from head to mouth after firing. After full length sizing that sets their shoulder back a thousandth or two, they lengthen almost a thousandth more. This adds about .001" to case length every shoot-reload cycle.

Most rimless bottleneck cases are driven by the firing pin's impact hard enough against chamber shoulders to set them back .001" or more before firing. I've seen .007" with nickel plated 308 Win cases. There's enough pressure to push primers out past case heads. Reduced loads 10% or more below maximum won't expand the case to chamber dimension from bolt face to shoulder. Best evidence is the primer sticks out past flush with case head because peak pressure wasn't enough to push the case head back to the bolt face reseating the primer.

Hatcher mentioned in his book, 30-06 case shoulders sometimes set back .007" before firing.
 
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i use to be in the brass biz.
typical lc 1x brass needs to be trimmed.
some not but the mix says if you are reproducing clone
lc ammo with a bullet crimp, you best trim.
all after small base and then fl sizing with a bushing.
m16/m4 seem to stretch cases, maybe on extraction.
 
Remove the expander from your FL die. Then set the FL to touch the shell holder. Now back up the FL die 1/2 turn.
Size one of your short cases and check the length to the shoulder. Slowly turn down the die and size you case. Check each sizing cycle.
Eventually the FL die will squeeze in the sides of the case wall until the shoulder starts to bulge forward. Then as you keep moving the die down the die will eventually reach a deoth where it starts pushing the shoulder back.

I like to set my die by expanding a case straight or by using a longer case. Then I turn the die down until the over length case is sized barely enough to permit the bolt to close with some drag. Size several cases to the drag fit dimension until you are sure of the exact chamber length. Write that number down and save it.
In the future you can set your die .002 shorter and be sure your sized cases will fit.
Keep in mind that variations in number of sizing strokes, speed of sizing, dwell at the top of the stroke, amount of lube applied and temper of the brass can all cause small variations in case length. Measure about 100 cases as you size each case and you will be able to detect the small variations. Some may need to be sized multiple times until you perfect your sizing technique.

Sizing a case 3 times with a 1/3 of a revolution between sizing will result in cases all exactly the same length. It is even better if you have the ram dwell 3 to 5 seconds in the full up position. This gives the brass time to creep into exactly the same length each time. You can verify this by checking cases as you size them.
 
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What difference does rifle type make?

If one reloads fired cases from any rifle, minimal case head clearance improves accuracy.
 
Bart B. said:
What difference does rifle type make?

If one reloads fired cases from any rifle, minimal case head clearance improves accuracy.
Click to expand...

I don't know what you did in 70's. But it matters to have a functioning Semi auto that will go bang every time while not over working the brass hence what most would like to see is .003 shoulder set back from the maximum all the while not sitting at the reloading press for hours on end rotating the brass with three strokes per case and dwell for 5 seconds at TDC. I surmised from the description the OP is shooting NRA high power and is need of a certain level of precision that will create perfect scores without wasting valuable training time of positional shooting. You know this well being a former shooter yourself.
I was not responding to you Mr Bobbit in my last reply... and find myself at odds replying to you now, after you blatantly insulted me on another forum basically calling me a dumb ass and cant read along or keep up as you say. so be it. So with that being said.. I will continue to ignore your posts and move along as life is too short to amuse the know it all's of the world.
Good day.
 
Rtheurer said:
I don't know what you did in 70's. But it matters to have a functioning Semi auto that will go bang every time while not over working the brass hence what most would like to see is .003 shoulder set back from the maximum all the while not sitting at the reloading press for hours on end rotating the brass with three strokes per case and dwell for 5 seconds at TDC. I surmised from the description the OP is shooting NRA high power and is need of a certain level of precision that will create perfect scores without wasting valuable training time of positional shooting. You know this well being a former shooter yourself.
I was not responding to you Mr Bobbit in my last reply... and find myself at odds replying to you now, after you blatantly insulted me on another forum basically calling me a dumb ass and cant read along or keep up as you say. so be it. So with that being said.. I will continue to ignore your posts and move along as life is too short to amuse the know it all's of the world.
Good day.
Click to expand...

Bart has got me time or two and best thing about him is he never made it big time as F-Class. Could you imagine what it was like being one of his team members and disagree with him. I think that's part of the reason none of his coaches or team members post anything about him, David Tubb and his father shot with him.
 
MMH said:
I am beginning to reload for a Compass Lake AR15 that I have. This rifle has a Bartlein barrel & a CLE chamber. I was checking the headspace dimensions of cases fired from that rifle and am confused with what I am seeing. Using a Hornady headspace comparator w/ the A330 bushing, the fired cases are 1.456" long and unfired cartridges are 1.458" long. How could new, unfired cartridges have a measured headspace that is longer than the fired cases?

How should I set up the FL die? I wanted to set the shoulder back a minimal amount (0.003").
Click to expand...
Was the fired brass deprimed when you measured the fired case? .002" could be the primer protruding past the face of the cup.
 
oldroper said:
Bart has got me time or two and best thing about him is he never made it big time as F-Class. Could you imagine what it was like being one of his team members and disagree with him. I think that's part of the reason none of his coaches or team members post anything about him, David Tubb and his father shot with him.
Click to expand...
I'll get you again.

Reason I "never made it big time in F-class" is I never shot F-class
 
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