Reading about the digital headsapce gage reminds me ....

F

frwillia

Guest
of something I noticed last summer. I bought a Hornady headspace gage that is used for much the same thing. It has a red socket that is fastened to the jaw of the digital calipers. It somes with a number of gage cylinders with different diameter holes for different cartridge cases that fasten in the socket.

I zero the calipers with no brass in the tool, then I can measure from the base to where that hollow cylinder contacts the case shoulder. I think this accomplishes much the same thing as the digital headspace gage discussed in another thread. Works for me anyway.

When I first got this instrument I de-primed (in my universal depriming tool) and then measured a fired .243 case and found it was 1.629" from the base to where the hollow socket contacts the neck. I lubed it, put it through my Redding FL resizing die, re-measured it and found it to be 1.631". The case grew 0.002" during resizing.

Same with my RCBS FL resizing die.

The brass chambers just fine, extracts easily, so I don't see a problem, but it struck me as odd that it resized to become longer.

Is this ususual?

Thanks
Fitch
 
frwillia said:
of something I noticed last summer. I bought a Hornady headspace gage that is used for much the same thing. It has a red socket that is fastened to the jaw of the digital calipers. It somes with a number of gage cylinders with different diameter holes for different cartridge cases that fasten in the socket.

I zero the calipers with no brass in the tool, then I can measure from the base to where that hollow cylinder contacts the case shoulder. I think this accomplishes much the same thing as the digital headspace gage discussed in another thread. Works for me anyway.

When I first got this instrument I de-primed (in my universal depriming tool) and then measured a fired .243 case and found it was 1.629" from the base to where the hollow socket contacts the neck. I lubed it, put it through my Redding FL resizing die, re-measured it and found it to be 1.631". The case grew 0.002" during resizing.

Same with my RCBS FL resizing die.

The brass chambers just fine, extracts easily, so I don't see a problem, but it struck me as odd that it resized to become longer.

Is this ususual?

Thanks
Fitch
Click to expand...


Not when you drag it over the neck expander. Great way to make and uneven neck by the way.
 
Big Al said:
Not when you drag it over the neck expander. Great way to make and uneven neck by the way.
Click to expand...

I suspected that. This is probably why folks who are really serious use a bushing neck sizing die? I lube the necks to make it easier for them to go over the expander but it should be much better if there is no expander.

When I started reloading I didn't think I'd ever get into this much detail, but it's clear the details are the difference between half MOA groups which are plenty good enough for practical varmint hunting and winning groups (half that size or smaller) in the ground hog matches at the club.

Fitch
 
frwillia said:
I suspected that. This is probably why folks who are really serious use a bushing neck sizing die?
Click to expand...
Fitch,

Even bushing dies can disturb the shoulder in some circumstances. Necks can expand quite a bit in factory chambers & squishing those large diameter necks back can concertina the shoulder a tad.

John
 
with std dies set up per the mfg instructions, you are sizing a lot of body pushing the oal of the case, so it is narrower and longer>>>brass has to go some where.
this is from body sizing and has little to do with the neck, tho pulling a button thru it does not help much.

mike in co
 
If the case was on its first firing, or had been previously fired with a low pressure load, the case might measure less than the chamber. It usually takes several warm load firings for the case head to shoulder dimension to stabilize at its largest value. If that is the case, then a die that was set up to just touch the shell holder, with no case, might have its internal shoulder surface farther from the shell holder than the measurement of the case being sized.This would leave some room for the shoulder of the case to "oil can" forward as the OD of the body was reduced in sizing. This is only one possible explanation. If you have other cases that measure the same, before sizing, as the one that you wrote of, you can try one with, and one without the expander ball, using the same die setting, to see if the expander is the culprit. Let us know what happens.
 
Boyd Allen said:
If you have other cases that measure the same, before sizing, as the one that you wrote of, you can try one with, and one without the expander ball, using the same die setting, to see if the expander is the culprit. Let us know what happens.
Click to expand...

Ok, I did an experiment (the reloading bench is only 8 normal steps from where I'm sitting as I type this).

I picked two Win fired cases out of the bin of probably 100, deprimed them in the RCBS universal depriming die, and measured them. They have been fired 5 times previously. Since this is for hunting ammo in my .243 sporter, I have always FL sized the brass. They measured 1.629" from the base to where the hole in the measuring instrument contacts the shoulder.

I removed the neck expanding button from my RCBS FL sizing die, cleaned it thoroughly as long as it was disassembled, made sure it was dry inside. It is adjusted to contact the case holder like the directions specify.

I lubed the cases with Redding case lube on a pad, then ran them into my RCBS FL sizing die and pulled them out again. It didn't take an inordinate amount of effort to push them in. Pulling them out there was some shuddering resistance and it felt like it took more effort to get them out than push them in. They both measured 1.631" where before they had measured 1.629". This is the exact same measurement I was getting with the neck sizing button in place.

Then, just to see what would happen, I ran them into the die a second time. This was a much smoother trip. When they were removed they both measured 1.6275" where just before they had measured 1.631".

The neck measured .276" OD before any sizing and .266 after being pushed into the die with out the expander after both trips.

The brass shows no sign of case thinning just above the base on the inside like my .22-250 brass does. There is no sign of neck cracking either like I sometimes get with the .22-250.

Fitch
 
Typically, if you adjust a FL die to touch the shell holder, and then size a case, leaving the ram at the top of its stroke, you will see a gap between the die and shell holder where there had been none. I attribute this to linkage slop, press give, sun spots, or bad mojo. Call it what you will, you can adjust into this gap. Years ago, when doing the same test using a .220 Swift case and RCBS FL die, the gap was .006. Try readjusting the die deeper into the press, a little at a time, and see what happens. I attribute the judder that you described to the die being dry...even though the case was lubed. Sizing tends to wipe off lube as it progresses. I predict that if you had done several more cases, the same way, it would have not happened again, or maybe one more time. Let us know what happens.
 
Boyd,

Interesting. I adjusted the die down to the point where I couldn't quite bottom the press with no shell case in there. Then I resized the two cases from last night and they came out 1.6230 - a full 0.0045 shorter than they were. I like the 1.627 result, which appears to be a 0.002" shoulder bump, so I re-adjusted the die back to there.

Thanks for the suggestions.

Fitch
 
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