223 case base to datum problems

[baczt]

Howa 1500 heavy barrel 223. Loading on Rock Chucker 2,Lee FL sizing die,RCBS charge master, verifying with RCBS 502 scale, Hornady comparitor with A330 bushing, new Starline brass, WSR primers, 53gr Hornady, 28.0 gr. CFE223. My base to case datum length keeps shrinking. New cases were sized to 1.456” cases were measured after sizing. After firing the BTCD shrank to 1.546 - 1.450. I resized these cases to 1.449 verifying each after sizing. Second firing the BTCD shrunk again. These cases now measure from 1.450 to 1.442. Rifle with a stripped bolt will close hard @1.458,close easy @1.546.
What am I doing wrong?

 

[Eagle Six]

That seems like a large fluctuation of measurements. Why are you sizing down to 1.449" when 1.456" fits well?

 

[baczt]

That seems like a large fluctuation of measurements. Why are you sizing down to 1.449" when 1.456" fits

That seems like a large fluctuation of measurements. Why are you sizing down to 1.449" when 1.456" fits well?

The majority of the first fired cases measured 1.450, I was thinking to keep a consistent datum length hop ing the cases would fire form uniformly.

 

[Eagle Six]

This has all the earmarks of taking a while!

Are all the sized cases measuring the same within a .001"?

Do you have any new unsized Starline brass left and if so what do they measure?

How many loads have you fired and is there any trend when you measure them? You give the range, but are most of them 1.546" or 1.450", or half and half?

It's been a long time since I have loaded 223 Remington, however I don't ever remember loading any cartridge that the cases after firing were 10-16 thousands shorter!

If it were me I wouldn't be bumping the shoulder back anymore than was needed to load without resistance, and that is commonly .002".

No doubt there is a trend you have identified. I think I'm missing something or you're missing something. Nevertheless, keep the information flows and between all the help on here, it will be solved.

 

[kyotekiller25]

There's gotta be some discrepancies with your measurements, or spell check on those numbers. It's hard to tell really. Cases don't normally shrink after firing. They typically expand to whatever the chamber is cut for. And why on earth are you sizing them down so much? .002" is all you should be sizing them back after firing.

We need some better/verified numbers I think to be able to help identify or diagnose the issue. Because what you're writing, doesn't make a whole lot of sense.

 

[fkimble@charter.net]

Sounds like the body portion of the chamber is oversized. Upon firing the pressure pushed the case wall out to the chamber wall, hence shortening the case. Why did you size new brass? Did it not chamber in your gun?

And per above "what you're writing, doesn't make a whole lot of sense." Glad it's not just me~

Frank

 

[baczt]

This has all the earmarks of taking a while!

Are all the sized cases measuring the same within a .001"?

Do you have any new unsized Starline brass left and if so what do they measure?

How many loads have you fired and is there any trend when you measure them? You give the range, but are most of them 1.546" or 1.450", or half and half?

It's been a long time since I have loaded 223 Remington, however I don't ever remember loading any cartridge that the cases after firing were 10-16 thousands shorter!

If it were me I wouldn't be bumping the shoulder back anymore than was needed to load without resistance, and that is commonly .002".

No doubt there is a trend you have identified. I think I'm missing something or you're missing something. Nevertheless, keep the information flows and between all the help on here, it will be solved.

Yes all of the cases sized with in .001 before firing.
New brass of the same lot measure either 1.455 or 1.456 I have 20 of them left.
Here is how the brass measured after second firing: 2ea@1.449, 2ea@1.448, 8ea@1.447, 13 ea@ 1.446, 24ea@1.445, 18ea@1.444, 15ea@1.443, 8ea@1.442.
Yes I plan to neck size and fire to see what happens.
Thanks for the reply

 

[kyotekiller25]

My new 223 lapua cases measure 1.457"-1.459"
New starline measure 1.455"-1.458"

So your virgin starline numbers are right where mine are.

My fired cases come out to 1.459"-1.460" It's a tight chamber spec 223 Wylde. I size them back down to 1.458"

I have no idea why your cases are shrinking .006"-.014" upon firing. Doesn't make much sense to me.

I'm curious what others have to say.

 

[baczt]

My new 223 lapua cases measure 1.457"-1.459"
New starline measure 1.455"-1.458"

So your virgin starline numbers are right where mine are.

My fired cases come out to 1.459"-1.460" It's a tight chamber spec 223 Wylde. I size them back down to 1.458"

I have no idea why your cases are shrinking .006"-.014" upon firing. Doesn't make much sense to me.

I'm curious what others have to say.

Thanks for all your replies, I have a typo in th first post my bolt closes easy @ 1.456 not 1.546 sorry for that.

 

[baczt]

Sounds like the body portion of the chamber is oversized. Upon firing the pressure pushed the case wall out to the chamber wall, hence shortening the case. Why did you size new brass? Did it not chamber in your gun?

And per above "what you're writing, doesn't make a whole lot of sense." Glad it's not just me~

Frank

I sized the virgin brass because the necks were dented and not uniform, looking back I should have just neck sized them.

 

[K22]

Thanks for all your replies, I have a typo in th first post my bolt closes easy @ 1.456 not 1.546 sorry for that.

I would like to help you, but I am totally confused by your data.

I literally load hundreds of 223 Rems a year for 10 different bolt rifles and never encountered the issue you described but I am not even sure if I understand the issue. I will try to simplify this issue.

Are now saying (latest post) the fired cases,1.456, chamber easy but not the 1.546?

These fired cases should represent a fire formed case head space to your rifle chamber. This should become your baseline and you should not have to bump the shoulder back. Set your F/L die for zero shoulder set back, size three fired cases and check in your rifle chamber. If they chamber without resistance, then this is your baseline case head space for that specific rifle.

Eventually you may have to bump the shoulder to .001 or .002 after several loadings. I have gone as many as 6 or so firing without having to bump the shoulder. I believe this is due the F/L die sizing the radial dimension of the case which often is a significant contributor to difficult sizing.

 

[Walt Krafft]

What kind of gage are you using?

 

[baczt]

What kind of gage are you using?

Hornady comparitor A330 insert

 

[Eagle Six]

Out of curiosity is your Howa new from the factory? If used, do you know of it's history? Is it a 223 Remington chamber? Should have nothing to do with. If the chamber was over sized all the fired cases should come out within .001".

The mystery continues. I just cannot follow that out of 90 rounds there is a .007" difference.

Thanks for all your replies, I have a typo in th first post my bolt closes easy @ 1.456 not 1.546 sorry for that.

I think maybe you have another typo in your first post.....

After firing the BTCD shrank to 1.546 - 1.450.

Should that 1.546 also be 1.456?

 

[Dolomite]

Check your calipers and comparator to ensure its installed correctly and measure again. The numbers don't make sense as to why it would shrink .010. A few thousands maybe but not .010. If the chamber was short your wouldn't be able to chamber a round and if its a long chamber the brass would grow longer.

 

[baczt]

Out of curiosity is your Howa new from the factory? If used, do you know of it's history? Is it a 223 Remington chamber? Should have nothing to do with. If the chamber was over sized all the fired cases should come out within .001".

The mystery continues. I just cannot follow that out of 90 rounds there is a .007" difference.


I think maybe you have another typo in your first post.....


Should that 1.546 also be 1.456?

Yes correct

 

[baczt]

Check your calipers and comparator to ensure its installed correctly and measure again. The numbers don't make sense as to why it would shrink .010. A few thousands maybe but not .010. If the chamber was short your wouldn't be able to chamber a round and if its a long chamber the brass would grow longer.

I used a second set of calipers to confirm the measurements, both calipers were verified with my micrometer standards @1”& 2”.
I agree cases shouldn’t become shorter they should grow longer.

 

[Richard Jones]

If you are able to edit your original post it might help and not cause issues for others in the future. It's very hard to follow the chain....

 

[grovey]

My base to ogive measurement seems to have shrunk some in my old age.

 

[dellet]

A few things to check

Is there any carbon below the neck and shoulder?
This would indicate low pressure and the case not sealing the chamber.

Check diameter.
The case may be expanding, but not stretching. This would cause the case to shorten. This should also confirm the chamber is not oversized.

Back the sizing die off a 1/2 turn or so. You want to be able to see on the neck that the shoulder has not been touched.
This will compress the sides of the case, and push the shoulder forward. If it returns to original length or close, it would confirm the expanding but not stretching theory.

Any chance a primer is above the base of the case when being measured?

Neck sizing only or a partial full length of a fired case, just enough to hold a bullet, might allow the case to stretch if it’s going to.

Chamber a case with the longest measurement. Maybe new un sized, see if the shoulder is pushed back on chambering, you never know.