223 sizing questions


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drsfmd
November 3, 2012, 10:24 PM
I'm not new to reloading, but I'm new to necked cartridges, so I'm in new territory, and a little out of my element (shotshells and straight walled pistol cartridges)

Setting up my press to load .223, and I'm curious about case sizing. My books indicate that 1.750 is the ideal length-- my question is how much wiggle room is there in that number? I sized 5 pieces of brass and came out with the following lengths: 1.7755, 1.7760, 1.7595, 1.7590, 1.7520, 1.7480, 1.7475, 1.7430, 1.7425, 1.7400.

Is that to much variation (or is that normal)?

I assume the first two are too long and need to be trimmed, but what about the others?

Is there such a thing as too short (I mean, I know the *obvious* answer, but I don't know what that number is).

Thanks for entertaining my dumb questions.

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peels
November 3, 2012, 10:42 PM
The variation can be due to different manufactures (if you are using mixed head stamp). Varying power of the load will also cause length variations. the hotter the load, the more the case will tend to stretch. Variation in headspace can also cause difference in case stretch.

The way I understand it, there is no issues with the case being too short, unless it is excessively short to the point where there is not enough neck tension, then you risk setback.

The only issue different length cases will cause is if you crimp your rounds, the crimp would not be consistent if you have varying length cases.

rg1
November 3, 2012, 10:44 PM
You need to trim any cases that are over 1.760" which is the maximum length and the most recommended trim length is 1.750". It's ok to load any case 1.760" or below. Bottleneck cases grow in length on every firing some more than others. Trimming back to 1.750 will usually let you fire the case 2-3 times before they grow past 1.760". Also the once fired factory or military surplus cases usually need trimming after the 1st firing. Most trim all cases as close as possible to the same length to make the ammo more consistent plus if you want to crimp the bullets having them the same length will make crimps more consistent.
The main thing sizing bottleneck rifle cases is "how much you push the shoulder back" and how much headspace you have after sizing. For this you need a tool to measure the shoulders of cases fired in your rifle and to measure how much your sizing die is pushing the shoulder back. Two reasons, one if you don't push the shoulder back enough the newly loaded round might not chamber in your rifle and second if you push the shoulder back too much you will get case stretching and a possible case separation. I use both the RCBS Precision Mic and Hornady's Headspace Gage Set. Both are good tools. Do some reading on headspace and adjusting your sizing dies correctly. Also you definitely need to trim bottleneck cases.

Walkalong
November 3, 2012, 11:38 PM
Size the cases to fit a case gauge. Trim everything over 1.750 back to 1.750. Anything 1.740 to 1.750 will work just fine. Shorter is not unsafe.

Sport45
November 3, 2012, 11:58 PM
Keep in mind that sizing doesn't affect case length ona bottleneck rifle case any more than it does on a pistol case. When full length sizing you are pushing the shoulder back to adjust headspace. That's the distance from the base to a datum point on the shoulder.

As mentioned above you trim after sizing. For best case life, size only enough for the case to fit in the chamber of your rifle. If the rounds are going to be used in multiple guns size for the shortest or just set it up to SAAMI minimum by letting the shell holder contact the sizing die at the top of the stroke.

Hondo 60
November 4, 2012, 12:36 AM
When sizing & deciding to trim, I keep 'em between 1.749 & 1.755.

Shorter gets dumped & if they're longer the whole box gets trimmed.

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