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I just got done resizing my first lot of brass (100) to start reloading. According to my loading manual (sierra) the case should be trimmed to 2.005 i have measured my cases and the all measure 2.003. What is the minimum length the case should be. I cant find that anywhere in the manual. Sorry for the newbie question i just want to be sure before continuing. I bought the brass from my local sporting good store so i figured it was new brass.

Thanks Again Crank
 

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I don't think I've ever seen any load books list a minimum, but if yours says 2.005, I wouldn't trim less.I've never used a Sierra load book either. If it's a bit less, and you never trimmed it, I wouldn't worry about it.It was a tad shorter when the manufacturer loaded it the first time.If it is used brass you purchased from an individual,it might be troubling. I've got some twice-fired Federal .308 brass that measures around 2.000. Sierra most likely doesn't wish you to undertrim, so they say 2.005 to be safer from liability.

.308 isn't a hot cartridge, so they generally grow slowly.

Jeff
 

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I've never seen a minimum listed but if you keep it around 2.005 you should be good. I've been told some highpower shooters trim to 2.000 but I usually keep mine around 2.005. Your cases are fine at 2.003.
 

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Yep, that's a good question I was asking myself.
I've resized my firsts (used) cases me too Monday night, and they were all too long, at 2.009". So I trimmed them, but the 2-3 firsts ones I trimmed went down to 2.001" and 2.002" since my trimmer was not yet adjusted properly.

And I would add that even now that I've set adjusting screws, I get results from 2.003" to 2.005" from one case to another...

I guess that's no big deal, but if someone can confirm that between 2.000" and 2.005" we're fine, that would be great.
 
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I trim to 1.995", then I don't have to trim again for the life of the case. No worries if you are within .030" of max. Within reason, you only run into problems if the case is too long. Most reamer designs have a 45 degree angle from the neck diameter to the throat diameter (freebore diameter) before the lead angle begins. When your case exceeds the length maximum, you start jamming the casemouth into the 45 degree area which has the effect of crimping the casemouth into the bullet's jacket, which of course then jacks up the pressure of the round, NOT GOOD.
 

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I'm with Jeff on that. I trim to length at 2.005, and seen it as little as 2.0032. Not a problem. NOT over 2.014 has been my rule. .002" neck tension for semi's - .003 for bolt action. So far, ain't blown myself up real good. HTH. Love this site, whenever I can find the time to chime in.
 

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According to mt No.5 Nosler book, 2.015 is maximum case length.Under that is useable, but 2.005 is what most folks trim them to.

Jeff
In reality, the maximum length is determined by the chamber in one's rifle. You want the case to be short enough so when it grows in length under pressures generated it doesn't "bottom out" on the second shoulder and pinch the bullet. Severe pressure spikes occur when this happens.

If you want to know what a maximum case length is for your rifle either buy a sinclair chamber length gauge or use some "Scratch Cover Crayon". Put a thick line from case mouth to the ogive of your bullet. Make sure the bullet is grease and oil free so the thick waxy crayon material will stick. The mark should be as thick as the case neck. When you chamber the loaded round the second shoulder will mark the wax and you can measure the distance from the end of the case to where the neck portion of the chamber transitions into the free-bore.

As for "too short"? As long as you have enough case neck to get a "3/4 of the "caliber" in a neck you aren't too short. For a .308 that would be around .250.

Just remember, the shorter the case the greater the chance of building up a carbon ring in the front of the chamber.


The 2.005" dimension is more of a recommended "Trim To" length. It's based on the assumption that once a case grows to 2.015", and you trim it to 2.005" you probably won't have to trim it ever again as the case will more likely fail (loose primer pocket, neck split, head separation).

I trim my cases after every firing and use a dimension of 2.010" I do it because I also anneal after every firing and want to make sure that the case mouth is nice and square, has a good chamfer, and a slight de-burring bevel. I use an RCBS 3-way cutter so it's a "one and done" process.
 

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SAAMI lists 1.995 as the minimum cartridge base to neck dimension. This is to provide sufficient next tension for keeping the bullet in place during handling and chambering. As for AR or Bolt, 308 chambers are the same minimum dimensions so it doesn't matter. The Semi-Auto chambers may be slightly larger in practice.
 
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