Increased case head size in fired brass...

[CT10ring]

Hello,

I'm reloading fired 22-243 brass - maybe 3-5 firings.

I'd guess loads on the mild side - never sticky bolt, nor overly flat primers, etc.
RL-22 42.0g w 73g bullet 1/8 twist. I shoot in high temps (PD towns) & want to err on safe side.

I'm F/L sizing w Redding die (non-bushing)

There is .002" growth fired vs. new brass at the very base.

If I re-size a case in die a 2nd time (just as a test), case still is tight on removal from die. that is, no more sizing down at base of case is provided by additional run thru press.

(Shoulder set back is a measured .0015 - .002". Runout with bullet loaded -- measured near case neck : .001-.003").

I loaded + shot with same brass 2 weeks ago to test a new load + bullets.
Good results, nothing odd in chambering, extracting. All normal.
All brass recently annealed (perhaps a bit under-annealed) by me.

I used a dental pick inside case near head to "feel" if a gap was forming indicating
possible case stretch. perfectly smooth.

Is this stretch normal? No shiny ring at base...
pix of new case head , fired case head and a sized case.

Thanks for any info--

 

[butchlambert]

And your question is? Seems normal to me from your posted info.

 

[riflewoman]

Does it continue to grow on subsequent firings. If so, and I suspect this, then the load is too hot and drop it 2 full grains.

 

[CT10ring]

the question: Is it normal for brass case head to stretch/grow ? .002" - safe?
I'm thinking so. Just checking with more experienced shooters. thank you

 

[Bart B.]

If you're referring to the slight bulge about 1/10th inch forward of the case extractor groove, that's a normal condition of a new case's first firing. Thats often called the pressure ring.

The case wall is thinner there than the metal behind it. Depending on the diameter difference between case and chamber at that point, the more it will expand. 2 to 3 thousandths is normal with new cases. Less with fired ones full length resized.

Happens all the time, even with reduced loads. Normal, safe thing.

If you're measuring the rim diameter change, .002" increase is probably way over safe pressures.

 

[LCazador]

A case head expansion of more than .001" is unusual. It looks like you may have an oversize chamber dimension. All the high pressure warning signs appear to be absent so I'd say the load appears to be safe. Are the primer pockets loose? By the way, measuring with a caliper is not the best way to measure head diameter. You want to use a micrometer that will measure to .0001", just a suggestion.

 

[gunsandgunsmithing]

Virgin case dimensions mean little, if anything. Are primer pockets loose? What does a sized case measure at the same point?

 

[ireload2]

1. You need to use a micrometer.. Your calipers are not good for better than plus or minus .001 on a good day.
2. If your heads continue to grow then your pressures are definitely too high for that brass. The brass is yielding no matter what the chicken entrails say.
Keep loading that hot and your primer pockets will leak.

 

[yotehater]

If I re-size same case a 2nd time, it still is tight on removal.

This statement is confusing. Tight on removal from chamber or die?

It looks like some kind of rough chamber marks or scratches on the brass shoulder in that picture.

 

[CT10ring]

If you're referring to the slight bulge about 1/10th inch forward of the case extractor groove, that's a normal condition of a new case's first firing. Thats often called the pressure ring.
This is exactly what I am trying to convey: "the slight bulge about 1/10th inch forward of the case extractor groove"
thanks for clarifying here...

The case wall is thinner there than the metal behind it. Depending on the diameter difference between case and chamber at that point, the more it will expand. 2 to 3 thousandths is normal with new cases. Less with fired ones full length resized.

"2 to 3 thousandths is normal with new cases."
Great, that's what I was thinking, also.

"Happens all the time, even with reduced loads. Normal, safe thing."
Good to hear.

"If you're measuring the rim diameter change, .002" increase is probably way over safe pressures."
I'm measuring the case head body above extractor groove (pictured in photos), not the rim.


thank you--

 

[CT10ring]

This statement is confusing. Tight on removal from chamber or die?

It looks like some kind of rough chamber marks or scratches on the brass shoulder in that picture.

Not the best worded description, I realize. Tight on removal of brass from die. The scratches are where I
test chambered the brass empty, unprimed, w/o firing pin assy just to get a feel for bolt close. I suspect the case hit the feed ramp, etc...

 

[CT10ring]

Virgin case dimensions mean little, if anything. Are primer pockets loose? What does a sized case measure at the same point?

Primer pockets are tight. New brass does have more "grip" in seating primers (BR2) than the fired brass; a typical occurrence I have observed. No primers feel loose.

1. You need to use a micrometer.. Your calipers are not good for better than plus or minus .001 on a good day.
2. If your heads continue to grow then your pressures are definitely too high for that brass. The brass is yielding no matter what the chicken entrails say.
Keep loading that hot and your primer pockets will leak.

understood, thank you.

 

[CT10ring]

A case head expansion of more than .001" is unusual. It looks like you may have an oversize chamber dimension. All the high pressure warning signs appear to be absent so I'd say the load appears to be safe. Are the primer pockets loose? By the way, measuring with a caliper is not the best way to measure head diameter. You want to use a micrometer that will measure to .0001", just a suggestion.

Got it thanks. Rifle is 2ndhand, reamer unknown. yup the chamber may be a tad big. there really is not a problem, except fired brass feels a bit tight in die on removal - like its not fully sized down at the very base. I just don't wan't to have my cases separate on firing because the brass is too stretched, and don't think it is. My measurements may well not be too accurate either. getting a micrometer.

 

[yotehater]

You provided good data. The chamber may be a little big. I've had some like that. The pressure ring growth is excessive on factory ammunition fired in it too.

Problems can come in if your FL die is having to set back that pressure ring excessively just to get the shoulder clearance needed. Then you might see incipient separation after a few sizings with that die. As a reloader though you have control over that. It is aggravating to have a die not working for your chamber.

Don't use any die setup that overworks your brass. Polish some out of the tight die or get a custom die made. A shaved shell holder is going to push the brass smaller there increasing the amount of stretch until you do see a case separation.

 

[CT10ring]

And your question is? Seems normal to me from your posted info.

normal is what I am hoping to have corroborated. thx sir.

 

[CT10ring]

Just re-measured cases with micrometer. I now doubt that my readings are truly reliable...
micrometer purchase next.

 

[ireload2]

Even a standard micrometer is not the best tool.
Go ahead and buy a good mike but keep an eye open for a good price on a blade mike. They are too costly for the avg handloader when new but they can measure the diameter of the extractor groove of rimless cases.

Just re-measured cases with micrometer. I now doubt that my readings are truly reliable...
micrometer purchase next.