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Old June 21, 2012, 07:41 AM   #1
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Question about .223 case length

The SAAMI case length for .243 Winchester is 2.025"-2.045". In .204 Ruger it's 1.830"-1.850". Both of these have a range of .020". However, the spec for the .223 is listed as 1.730"-1.760" which is a .030" range. If my math is correct, it doesn't appear that either length will allow for a full caliber length of bullet seating in .223.

If you're reloading for an AR, is there any advantage to one end of the specification versus the other? Thanks.
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Old June 21, 2012, 08:13 AM   #2
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Seems that 1.750 is a pretty common length to trim to
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Old June 21, 2012, 09:41 AM   #3
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Haven't noticed any difference in performance of different OALs within the range.

"Max" length is 1.76". "Trim to" is 1.75".

My OALs (55FMJBT only) work out to the ~2.240-2.255 range.

OAL will also depend on and vary with the bullet weight and type. They vary from 40 all the way up to 80.
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Old June 21, 2012, 03:32 PM   #4
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"... it doesn't appear that either length will allow for a full caliber length of bullet seating in .223"

Quite a few cases don't have caliber length necks. ???

Don't think SAAMI specs "trim-to" lengths. Modern loading books list an arbitrary trim-to at 10 thou less than max for those timid souls who fear making a decision on their own. Long before they started doing that I choose 5 thou less than max for myself, and that's what I still aim for, but I know I'm not going to blow anything up if I go shorter. (And I know exactly how long each of my chambers are so I also know how much longer I can go without blowing anything up.)

Last edited by wncchester; June 21, 2012 at 03:45 PM.
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Old June 21, 2012, 04:01 PM   #5
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Agree with wncchester, my trim length is 1.755, and I'll accept any case between 1.750 and 1.760. Or in other words, my target length is 1.755 and I'll accept a +/- 0.005. I do not load for absolute precision though.

I think if you're loading for precision, then every factor counts to some level. So a consistent case neck would one of those factors, and if you use a crimp, and I'm pretty sure you do, then that consistent neck length should hit the die at the same spot every time.

If not loading for serious precision, then I wouldn't worry about it.
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Old June 21, 2012, 04:03 PM   #6
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You are correct. That's why the .222 is almost always more accurate. BTW, the .204 is based on the .222 Rem Magnum case.

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Old June 22, 2012, 01:44 AM   #7
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i trim mine to 1.755 also, never had a problem. I am loading my ammo for an AR-15, plus I taper crimp all my ammo about .0015-.002"
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Old June 22, 2012, 12:00 PM   #8
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223/5.56mm Case Length.

If you're reloading for an AR, is there any advantage to one end of the specification versus the other?
Longer would be better than shorter. Longer provides more neck tension. This is needed for an auto loader. Military ammo requires a bullet pull of 45 lbs. As other have said, use the standard trim to length. Not the minimum usable length listed by SAAMI.
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Old June 23, 2012, 02:07 AM   #9
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I stay on the longer side also. As long as they are all consistently the same length then thats best. You can trim to a shorter length case as was noted, but the potential problem in shorter necks is there has to be enough neck to hold the bullet securely. (neck tension). This is why longer is better.

If you want to trim short for whatever reason, trim a few cases and seat bullets and test them against a bathroom scale to 50 lbs and see if the bullet moves. If it gets shorter, you need more neck.
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Old June 25, 2012, 06:11 PM   #10
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I trim my AR-bound .223 brass to 1.740" when using the RCBS X die, per instructions. I then don't have to trim again. I've used o.a.l. out to 2.270"-or-so, but I'm having to load as short as 2.200" for some of my ARs.
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