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Old June 22, 2009, 09:55 PM   #1
LuckyStrike
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.308 OAL Question

I re-sized some Black Hills .308 brass today. My first time doing this. I'm using an RCBS full length sizing die. The OAL of the once-fired-brass was 2.008 and after going through the die it was 2.012. This was roughly how most of the shells acted.

Maximum OAL for .308 is 2.015 and the recommended trim-to OAL is 2.005.

Is it okay that the shell got longer in the FL die? Is there a 'standard' OAL that the Die should be setting the brass too?

Do you recommend that I keep the brass at about 2.012-ish and start seating bullets or should I trim the case to a shorter OAL?

I also have a Lee Collet neck sizing die. My understanding is that once I have fired rounds from my rifle I can use this Collet die to neck size the brass and the OAL should at that point be 'fire formed' to my chamber?

Any help is much appreciated!
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Old June 22, 2009, 10:03 PM   #2
Unclenick
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What you saw is normal. Sizing narrows the brass and the excess has to go somewhere, so it squirts up into the neck.

The reason for trimming is to prevent the case neck from getting so long it jambs into the chamber throat, making it hard to let go of the bullet, and thereby raising pressure significantly. The SAAMI compliant chambers (all commercial chambers that aren't defective) have enough extra room in them so it is safe to load a maximum length case. If they didn't, the maximum would be shorter.

Cases that come out of the sizer over maximum need to be trimmed for safety's sake. I usually try to keep brass with the same load history all together in a group, and the first time one goes over length, I trim the whole group.

The collet die is a good neck sizing system. It doesn't move as much brass, but keep monitoring the length anyway.

By the way, the actual SAAMI spec for the .308 case is 2.015" +0 / -0.020". So you could shorten it all the way to 1.950" and still be within spec. Mostly trimming is aimed at the midpoint between minimum and maximum just to avoid having trimmer variance take the case outside the limits.

Nick
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Old June 22, 2009, 11:46 PM   #3
30Cal
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"OAL" means the length of the loaded cartridge. Case length is what you're talking about here.

The cases will continue to grow each time you size them. If they exceed the max (2.015") you have to trim. There are some guys that trim each time to keep them all the same. I hate trimming; I do it every other time (all of them at once).
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Old June 22, 2009, 11:51 PM   #4
LuckyStrike
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Thanks for the info guys!
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