ONCE FIRED VS. NEW, SHOULDER MEASUREMENT

[7887mm08]

So I am ready to try some new load workup for a rem 788 in 222. I have bought a new press since
I last loaded for this caliber. I got out my Sinclair shoulder bump gauge I checked about 20 once fired rem cases and 10 lapua cases and all measurements were within .001". For the heck of it I measured 10 NEW lapua cases. WOW! .014" SMALLER THAN FIRED CASES. I would expect them to be smaller but this seems a lot. So what is this telling me? Thanks Gary

 

[Dusty Stevens]

It tells you that you need to fireform them in your chamber to get a proper measurement

 

[bugman]

It tells you that you need to fireform them in your chamber to get a proper measurement

Yes, and it also tells you not to do any significant L trimming or uniforming (other than a slight bevel/chamfer) because those new cases will really change dimensions once you fireform them.

Jack

 

[BoydAllen]

One more thing: Generally there is no need to bump back from your once fired measurement. I usually try to make an example case by neck sizing several times to produce a case that is tight head to shoulder as an example of the maximum dimension that you will be bumping back from. In those cases where I do not have the time or opportunity to produce such a case (which I mark and save as a reference) I set the die to produce a head to shoulder dimension that is the same as the fired case, assuming that the first firing was not with a light load. One think that I only figured out after a number of years is that instead of having to come up with a punch base and hammer to decap a fired case before measurement, it is a lot easier to simply use my hand priming too to reseat the fired primer well below flush.

 

[22BRGUY]

One more thing: Generally there is no need to bump back from your once fired measurement. I usually try to make an example case by neck sizing several times to produce a case that is tight head to shoulder as an example of the maximum dimension that you will be bumping back from. In those cases where I do not have the time or opportunity to produce such a case (which I mark and save as a reference) I set the die to produce a head to shoulder dimension that is the same as the fired case, assuming that the first firing was not with a light load. One think that I only figured out after a number of years is that instead of having to come up with a punch base and hammer to decap a fired case before measurement, it is a lot easier to simply use my hand priming too to reseat the fired primer well below flush.

+1 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

 

[Brians356]

WOW! .014" SMALLER THAN FIRED CASES. I would expect them to be smaller but this seems a lot. So what is this telling me? Thanks Gary

That seems a bit excessive, but .010" is not atypical in SAAMI chambers. It goes to show that dire warnings about excessive headspace need to be tempered by the fact that normal headspace is fairly substantial with unfired brass and factory ammo.

SAAMI spec for 222 Rem chamber "headspace dimension" is min 1.2936 - max 1.3036.

SAAMI spec for 222 Rem cartridge is 1.2966 - .007. So the minimum cartridge is 1.2896.

Maximum chamber minus minimum cartridge is .014". Coincidence?

SAAMI rifle specs available here:

http://www.saami.org/PubResources/CC_Drawings/C and C Dwgs - TOC - Rifle.pdf

 

[7887mm08]

+1 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

so I guess then that using the same loads from a new case to a fired case could give different results and possibly different pressures. This is the first time that I have used the bump gauge. well I guess I can use my old load for the new cases to fire form them and then do all my new development with once fired cases. I guess I still have a lot to learn! Thanks

 

[Brians356]

so I guess then that using the same loads from a new case to a fired case could give different results and possibly different pressures.

While it's true load development begins in earnest with once-fired (fireformed) cases, consider that many folks report little if any difference in performance between the fireforming load (with bullet) and the same load fired again in an Ackley Improved cartridge. The shoulder moving forward .014" seems little enough compared to blowing out an A.I. case.

 

[7887mm08]

While it's true load development begins in earnest with once-fired (fireformed) cases, consider that many folks report little if any difference in performance between the fireforming load (with bullet) and the same load fired again in an Ackley Improved cartridge. The shoulder moving forward .014" seems little enough compared to blowing out an A.I. case.

Yeah go figure. For the half dozen guns that I reload for all my loads are with new brass! Now I am not loading for bench rest quality ammo, I am a hunter and when I find a load that consistently groups under 1 inch at a hundred I am happy. Some of these are honest half inch loads and that's a bonus. I stop and I'm happy. It has gotten to the point that almost all the brass for all the calibers is now once fired. I guess I am going to have to work up to all my favorite loads again. Oh well more time at the range is not a bad thing.

 

[Brians356]

It has gotten to the point that almost all the brass for all the calibers is now once fired. I guess I am going to have to work up to all my favorite loads again. Oh well more time at the range is not a bad thing.

Well you might load up a handful of the same load in the fired cases first, in case it's accurate enough to avoid starting over again. Given your accuracy requirement it just might be fine.

I started reloading by, well, "reloading" expended factory ammo. It was many years before I ever bought any brand-new cases, and I wasn't sure quite what to do with them! Many necks were out of round and case mouths uneven and lumpy (long before "premium" brass was available.)

 

[jsthntn247]

Seems typical for Remington. Looks like you got a 222 factory improved

 

[LCazador]

Yeah go figure. For the half dozen guns that I reload for all my loads are with new brass! Now I am not loading for bench rest quality ammo, I am a hunter and when I find a load that consistently groups under 1 inch at a hundred I am happy. Some of these are honest half inch loads and that's a bonus. I stop and I'm happy. It has gotten to the point that almost all the brass for all the calibers is now once fired. I guess I am going to have to work up to all my favorite loads again. Oh well more time at the range is not a bad thing.

One thing about loading for the 788 is that it is a rear lug gun and cases will tend to stretch with each firing. So it's not only important to bump the shoulder for consistent ballistic performance, but also to keep cases within chamber dimensions. Fireform your new brass first and then tune your loads to your rifle and have fun doing it!

 

[fguffey]

For the heck of it I measured 10 NEW lapua cases. WOW! .014" SMALLER THAN FIRED CASES. I would expect them to be smaller but this seems a lot. So what is this telling me? Thanks Gary

I do not do it for the heck of it; I measure the length of the chamber first from the shoulder of the chamber to the bolt face. I have one rifle that has a long chamber, for me that is not a problem; it is a 30/06 Eddystone that went through Utah and cam out with a chamber that is .002” longer than a field reject length chamber.


Instead of chambering a round and firing just to see what would happen I adjusted the die off the shell holder .014” then formed 280 remington cases to 30/06. When finished I had the .002” magic clearance between the case head and bolt face.


Beyond that there is the confusion surrounding ‘what would happen if I had chambered a minimum length/full length sized case in the long chamber?’. I would say the shoulder on the short case would not have moved.


F. Guffey

 

[Hondo]

When the case is short for my chamber .007" should I jam the bullet in order to keep the head of the case against the bolt when firing the case for the first time.

 

[Brians356]

When the case is short for my chamber .007" should I jam the bullet in order to keep the head of the case against the bolt when firing the case for the first time.

That's well within SAAMI spec, so why do anything? Factory ammo has at least that much headspace and beaucoup bullet jump, and the case usually comes out fine. Besides, I don't believe jamming the bullet holds the case against the bolt long enough to make much if any difference.

 

[savagedasher]

So I am ready to try some new load workup for a rem 788 in 222. I have bought a new press since
I last loaded for this caliber. I got out my Sinclair shoulder bump gauge I checked about 20 once fired rem cases and 10 lapua cases and all measurements were within .001". For the heck of it I measured 10 NEW lapua cases. WOW! .014" SMALLER THAN FIRED CASES. I would expect them to be smaller but this seems a lot. So what is this telling me? Thanks Gary

It all depends on your chamber . Myself I like checking my shoulder wit the firing spring removed when the bolt start to click set them back till you don't have the bolt fall . Larry