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

[711rollerdog]

Full length or neck size (without bumping the shoulder)and shoot 1-2 more times. It will show +....

 

[memilanuk]

How could new, unfired cartridges have a measured headspace that is longer than the fired cases?

Try this: take a new unfired round. Measure the headspace to the shoulder using the correct comparator. Carefully check that the primer is flush or below flush with the case head. Load it in the mag. Point the gun in a safe direction (may want to do this at the range, depending on your level of comfort/paranoia), hit the bolt release and let the bolt strip the round and chamber it like it would during normal operation. Extract the *unfired* round, and re-measure the headspace.

It is possible for the mass of bolt carrier to shove the shoulder back. It's also possible for a primer sitting 'proud' before firing to get either seated more fully by the firing pin, or just pushed in when everything goes 'bang' and the case head is thrust back against the bolt face under load. It's also possible that if this brass is new/virgin, which assuming factory ammo and not reman it probably is... that the shoulder angle of the virgin case isn't quite the same as the fired case. That can cause some weird variation in readings with your comparator.

As others have said, I'd worry less about comparing the headspace of virgin brass on factory ammo to once fired, than I would about just setting the die so it bumps the shoulder a given amount (3-4 thou) from the fired condition. After *that*, then yeah, pay close attention to the dimension after firing your reloads. The 2x fired headspace should match your 1x fired headspace pretty closely.

 

[Bart B.]

Why would you, when you shoot half moa groups at distance from a sling?

C'mon, post the pic. You know you wanna

Yawn....... ...... ... .

 

[Bart B.]

Try this: take a new unfired round. Measure the headspace to the shoulder using the correct comparator. Carefully check that the primer is flush or below flush with the case head. Load it in the mag. Point the gun in a safe direction (may want to do this at the range, depending on your level of comfort/paranoia), hit the bolt release and let the bolt strip the round and chamber it like it would during normal operation. Extract the *unfired* round, and re-measure the headspace.

It is possible for the mass of bolt carrier to shove the shoulder back. It's also possible for a primer sitting 'proud' before firing to get either seated more fully by the firing pin, or just pushed in when everything goes 'bang' and the case head is thrust back against the bolt face under load. It's also possible that if this brass is new/virgin, which assuming factory ammo and not reman it probably is... that the shoulder angle of the virgin case isn't quite the same as the fired case. That can cause some weird variation in readings with your comparator.

As others have said, I'd worry less about comparing the headspace of virgin brass on factory ammo to once fired, than I would about just setting the die so it bumps the shoulder a given amount (3-4 thou) from the fired condition. After *that*, then yeah, pay close attention to the dimension after firing your reloads. The 2x fired headspace should match your 1x fired headspace pretty closely.

I have observed new 308 Win and 30-06 primed cases (no powder, bullet) shoulders setting back .002" to .007" when fired. 2 to 3 ounce firing pins striking primers at 9 to 10 fps was the cause.

Hatcher's Notebook mentions his observations that new 30-06 case shoulders setting back several thousandths when chambered in rifles and machine guns.

Live rounds of new nickel plated 308 Rem. cases I tested with 13 to 14 percent reduced charges ended up with shoulders set back .006" to .007" and primers pushed out past case heads about the same amount. Max loads in new cases ended up with flush primers and .001" to .003" more case headspace. All case lengths shortened .002" to .003".

 

[Dusty Stevens]

Yawn....... ...... ... .

Where have you been mr bart? You dont post much anymore.

 

[Rsadams]

I have seen many many new brass that is to long or way to short , that little bit could have been not having the case head flat against the calipers etc etc.. Just fire them , set them back .002-.003....You may have to readjust as you get a couple of firings on them... I run all new cases through a full length die before loading so they all start the same... That's just me though , the AR platform is so hard on brass and sometimes they get lost so I know I am not going to get a ton of reloads off them anyway...

 

[Bart B.]

.223 headspace numbers from SAAMI:

Case, 1,4596 min, 1.4666" max

Chamber, 1.4636" min, 1.4736 max

Headspace gauge, 1.4636" GO, 1.4736" NO-GO

 

[memilanuk]

Not really relevant... good to know, but not really relevant.

The comparator he's using gives him relative numbers, which will almost *never* match the SAAMI spec numbers (if they do, go buy a lottery ticket). The numbers that matter are what he measures, not whats on some print sheet.

 

[Uncle Ed]

You can calibrate the Hornady cartridge case headspace gauge using feeler gauges between the two sections of the gauge. My Hornady gauge was reading .011 shorter than the Field gauge so I used a .011 feeler gauge between the red and silver sections to adjust the gauge.

Below a Colt Field gauge at 1.4736

comparator

Below the Colt Field gauge in the Hornady comparator gauge,

Below a fired case from my AR15 at 1.4675 and a idea of actual chamber headspace minus brass spring back.

 

[dsculley]

If you have any questions/issues call Compass Lake Engineering and talk to Mr. White. He is a fountain of knowledge and a very good shooter as well. If this is your first Compass Lake rifle you will soon find that he builds AR's that are second to none.

 

[gdbleb]

If you have any questions/issues call Compass Lake Engineering and talk to Mr. White. He is a fountain of knowledge and a very good shooter as well. If this is your first Compass Lake rifle you will soon find that he builds AR's that are second to none.

I have the very same upper components (Bartlein barrel & CLE chamber). I saw the exact same shoulder setback just chambering a round in a CLE AR. Try it without firing to verify. I called and asked Frank White, who is, by the way a great guy and has an infinite amount of patience for these types of learner questions. He said it was perfectly normal. Don't hesitate to call them and ask for him. The quality of his support matches the quality of his product.