I don't understand this.

J

jmcasto

Guest
Greetings. I am a long-time reloader but relatively new to the level of detail with respect to measuring the shoulders on brass. I'm confused by what I'm seeing and I'd appreciate any thoughts and advice you might have.

Last week I prepped some new .222 Lapua brass, to include turning necks, cleaning up primer pockets and full-length resizing with an RCBS Bench Rest die. I used a Whidden Case Guage (a lovely tool) to set the sizing die up. I seated the bullets to touch the lands of my rifle (using a Hornady Length Guage) and took them to the range. Everything went fine at the range and I was pleased with the accuracy, despite firing and fire forming of new cases.

Today I was measuring the shoulders on the cases in preperation for reloading and was surprised to find a + or - .008 headspace in the brass. I used both the Whidden Guage and my Fowler-Sylvac indicator (see picture below) and measured the cases several times to get consistent readings. I'm pretty confident the measurements are correct. I also measured the concentricity of the shoulders at the approximate "headspace datum" and the cases vary by no more than .0005, so I don't think case concentricity is contributing to the case length variation. My questions are: (1) Why such a large variation in cases fired in the same rifle? (2) Most importantly, considering the .008 variance, how do I set up my sizing die to get the often-recommended .001 shoulder bump? (3). What the heck am I missing or not understanding?

Best regards,
Joel
 

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Is the chamber some sort of improved chamber or standard .222?
What rifle action and barrel?
The people that want to help need more information to give you a reasonable solution.
 
jmcasto said:
Greetings. I am a long-time reloader but relatively new to the level of detail with respect to measuring the shoulders on brass. I'm confused by what I'm seeing and I'd appreciate any thoughts and advice you might have.

Last week I prepped some new .222 Lapua brass, to include turning necks, cleaning up primer pockets and full-length resizing with an RCBS Bench Rest die. I used a Whidden Case Guage (a lovely tool) to set the sizing die up. I seated the bullets to touch the lands of my rifle (using a Hornady Length Guage) and took them to the range. Everything went fine at the range and I was pleased with the accuracy, despite firing and fire forming of new cases.

Today I was measuring the shoulders on the cases in preperation for reloading and was surprised to find a + or - .008 headspace in the brass. I used both the Whidden Guage and my Fowler-Sylvac indicator (see picture below) and measured the cases several times to get consistent readings. I'm pretty confident the measurements are correct. I also measured the concentricity of the shoulders at the approximate "headspace datum" and the cases vary by no more than .0005, so I don't think case concentricity is contributing to the case length variation. My questions are: (1) Why such a large variation in cases fired in the same rifle? (2) Most importantly, considering the .008 variance, how do I set up my sizing die to get the often-recommended .001 shoulder bump? (3). What the heck am I missing or not understanding?

Best regards,
Joel
Click to expand...

Lissen to Dusty, REALLY lissen, and thinkabou'dit.....



And now I'll opine some;


FIRST of all, if you read in a manual somewhere about "setting the resizing die to touch the shellholder" please do yourself a favor and RIP THAT PAGE OUT OF THE BOOK before someone gets hurt. You're only ALLOWED .004 headspace between GO and NO-GO gauges. And if you bring a gun to a "gunsmith" and it closes on the NO-GO he'll most'n likely raise a stink...... especially if he's a "Trained And Accredited Facticory Technicalician" of some brand or another so your variation of 8 thou is severiously out of spec. JUS' Sayin'.....my guess is that you've run these new cases through a die so's you could do all this "truing work." And that you reset the factory shoulders even forevermore farther out of whack than they were. If you insist on doing this, please make sure the die is backed 'way up off'n the shoulder. And if you DIDN'T, then may I reiterate, something's out of whack.

SECONDLY, (and this is an aside, I know you din't ASK for it) the only way you'll ever get truly straight and stable cases is if you first fireform from a crush-fit, meaning you should somehow be able to make cases so long that they only go into the chamber with some fairly stout pressure, that they be bearing firmly on the brass of the shoulder somehow. I misdoubt you care enough but IF YOU DO, then you must use an "expander mandrel" to expand your brandie new casenecks up to say 7mm, then run them thru the die such that the "False Shoulder" thus produced makes for a jam-fit.


That said, you'll be able to get fairly usable cases by "seating the bullets long" although the gain over just NOT SIZING THE FACTORY CASES BACK will be small. And someone will sooner or later suggest you grease your chamber.... (I will NOT....I think greasing a chamber is lunacy)

But, if you're honest, and if you're careful, and if you're true, and if you take careful note and careful notes...... you will sooner or later realize that actually achieving that "resizing under a thou" is particularly vexing.

And THAT said, there are maniacs like me that require that EVERY accurate rifle in the arsenal, calibers up to 338 Lapua and 50BMG do indeed meet this stricture.

And DO what needs to be done to achieve this

always

al
 
I have found new brass to be shorter to the shoulder than minimum headspace, sometimes by several thousandths, so I find it unlikely that your running it through a FL die before its first firing pushed the shoulder back, and even if that had occurred, the effect would have been uniform. What I think happened is that you loaded to a pressure that was right on the edge of giving consistent fire forming, and some did, and some did not. In the case of those that did not, with low pressure, sometimes fired cases are shorter to datum than before they were fired. Did you notice if any primers were protruding above the heads of your fired cases? In any case, a safe but stout load should take care of the differences. Another thing that can contribute to this is (when combined with a light load) a chamber that is a bit on the rough side.
 
Listen to Dusty. do not worry about headspace, it is what it is, in a custom chamber. only matters if shooting factory ammo
 
This
with low pressure, sometimes fired cases are shorter to datum than before they were fired.
Click to expand...
The body of the case expands outward, pulling the shoulder back. And its possible for the firing pin strike to set the shoulder back .006" (223 Rem). Midrange or low presssure will not expand the case back to the size of the chamber. (head to datum)
 
First- you must set your dies up to your chamber- lay down the measuring tools for this. Pull out your firing pin and start the die down til the bolt almost goes all the way down til you feel it at the bottom. Yours may not do this just yet.
Second- you need to jam your bullets hard in this case- seat em long til closing the bolt seats em.
Third- use the softest primers you can so the firing pin doesnt push them forward.

Like al i would never grease a chamber or use lube on the necks- body only. Give this a try and let us know how it goes. Be careful and ask plenty of questions.
 
Ok

Thanks for the thoughtful comments.

To answer some questions -
This is a standard .222 Remington, fired in a Remington 700V, factory chamber. The load was: 20g. H4895, 55g Sierra bullet, Remington BR primers. OAL 2.220 (I thought this was long enough based on the Hornady Lock and Load reading but I'm rethinking that).

Based on the comments so far, I just went to my reloading bench and looked at the cases that haven't been de-primed yet and was gobsmacked to find a few cases where the primer stands proud. All primers were all poperly seated during reloading and I'm embarrassed I didn't see/notice the proud primers in the fired cases while at the range. Lesson learned.

Here's my takeaway. The fireforming process is not complete. The cases shorten during fire forming, giving me the shorter measurements (I had not thought about the shoulder datum measurement getting shorter, only the overall case length). I need to ensure a crush fit so the case head is pushed back flush against the bolt head.

I appreciate your patience as I wrap my head around concepts I had not expected.
 
I'm concerned that you're sizing the case too much. Check the base to shoulder measurement (on a fired case using the same measuring device) before and after sizing to ensure the die is adjusted properly. If the resulting measurement is more than a couple of thousandths difference,,,and three thousandths feels the same as two when chambering an empty case,,,stop right there. The case is not too long but rather has become too fat near the base. If you indeed know that you're not oversizing the case - nevermind!

Perhaps somebody that understands what I'm trying to say here can explain it better.

Also, you very likely can skip some of the stuff you're doing based on the rifle you have. Turning the case necks when shooting a factory chamber can often hurt more than help. If you continue to turn the necks, just turn them enough to partially clean off the thick spot. Be sure to shoot some unturned necks to see if you even need to do that.
 
Best guess is the 20 gr charge is way UNDER for fire form load.
Maybe 2600fps at 28kpsi
You meed to move up in steps.
Get a good loading manual and use it.
Heck go on line and look at mfg load data.
 
The primers arent sticking out cause you did it- theyre standing out because they were pushed out as your firing pin pushed the case forward because you had too much headspace. Remember below min loads are just as dangerous as overcharged loads. You should be between min and max of a popular powder listed in a manual.
 
jmcasto said:
Thanks for the thoughtful comments.

To answer some questions -
This is a standard .222 Remington, fired in a Remington 700V, factory chamber. The load was: 20g. H4895, 55g Sierra bullet, Remington BR primers. OAL 2.220 (I thought this was long enough based on the Hornady Lock and Load reading but I'm rethinking that).

Based on the comments so far, I just went to my reloading bench and looked at the cases that haven't been de-primed yet and was gobsmacked to find a few cases where the primer stands proud. All primers were all poperly seated during reloading and I'm embarrassed I didn't see/notice the proud primers in the fired cases while at the range. Lesson learned.

Here's my takeaway. The fireforming process is not complete. The cases shorten during fire forming, giving me the shorter measurements (I had not thought about the shoulder datum measurement getting shorter, only the overall case length). I need to ensure a crush fit so the case head is pushed back flush against the bolt head.

I appreciate your patience as I wrap my head around concepts I had not expected.
Click to expand...

From your "gobsmacked" remark I'll assume that you're aware of WHY the primers are standing proud, but for the folks reading this who may not, I'll explain.

The primers are popped up because the "head" of the case never came back to the boltface. In other words you could have had the barrel in your hand and fired it using a hammer and a nail and THE CASE WOULD NOT HAVE POPPED OUT OF THE CHAMBER.

This is perfectly normal. As has been proven repeatedly through testing.

The brass case contained the pressure without stretching or in engineering vernacular "yielding."

And since it did not slip, the primer tried to leave.....

It takes 40-50,000psi to stretch the case and a clean, dry case in a clean dry chamber WILL NOT SLIP unless pressure is so very low as to cause leakage around the case, which will cave the case inward destroying it. A clean, dry case in a clean dry chamber WILL NOT SLIP BACK under usable loads.This has nothing to do with "smoothness" in the chamber IME. My testing and the testing of others has in fact shown that mirror polished chambers tend to have the highest 'stiction,' and I personally have several chambers with huge, fingernail-hooking rings that show no tendency to be sticky. I've conducted tests using chambers polished from 180 grit to mirror polished to find that roughly cross-hatched chambers which "frost" the brass are no more sticky than smooth. I only say this to illustrate that I'm not making this statement casually.

The Brass Case WILL Stay As Far Forward As The Firing Pin Pushes It.

It WILL.

So the only way to get your headspace back if your chamber's long is by firing the cases hot enough to streetcchhh the caseheads back until they meander willy-nilly into the vicinity of the boltface.

And if you'll do some testing without powder by soaking some primers for a week in MEK you'll find that only a false shoulder will reliably hold the case back for fireforming. A false shoulder set so far forward that you must force the bolt handle home with pressure......preferably MORE pressure than the firing pin can generate, like 10-15lb.

Enjoy The Journey :)

al
 
Al,
Let me politely disagree. It is not a matter of the whole case sliding back. This can (lubed case) happen but it is not the common mechanism. What is involved with a dry new case in a dry chamber is a one time stretching that if repeated several times to the same extent, would produce an incipient, and then an actual separation just in front of the head. This is why over bumping shoulders will lead to the same thing.
Boyd
 
Boyd Allen said:
Al,
Let me politely disagree. . . . . .
Boyd
Click to expand...

Boyd,

I have absolutely no idea where it is we disagree so I'll just have to leave it at "Thank You."

You're a credit to BRC in the way you patiently share your acquired knowledge year after year.

al
 
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