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#7050960 - 01/24/18 08:03 AM trim length
garyrapp55 Offline
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Registered: 12/26/11
Posts: 528
Loc: Ft. Worth
Last night I had to stay up til 10 because I'm on-call this week so I was prepping some cases. I measured length and these cases were varying as much as .006 and were all the same before last loading. Is this normal after resizing?

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#7050981 - 01/24/18 08:24 AM Re: trim length [Re: garyrapp55]
ChadTRG42 Online   happy
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Registered: 09/16/09
Posts: 12221
Loc: Lewisville, TX
Yes. .006" is fine for a little variation. As you shoot and resize, some cases will expand more than others. That's fine. With good case prep and consistent powder charges, .006" won't cause any issues what so ever.
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#7051008 - 01/24/18 08:40 AM Re: trim length [Re: garyrapp55]
garyrapp55 Offline
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Registered: 12/26/11
Posts: 528
Loc: Ft. Worth
So for 308 anything between 2.005-2.015 is good to go, or should there be a maximum accepted variation?

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#7051011 - 01/24/18 08:42 AM Re: trim length [Re: garyrapp55]
redchevy Offline
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Registered: 10/25/04
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Would it matter what they are for? I wouldn't worry about it for uncrimped ammo, but is that enough variation to give you any issues with calibers that head space off of the case mouth like 9mm etc.? or enough variation to mess with crimping/roll crimping? If I'm crimping I always trim cases.
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#7051126 - 01/24/18 10:03 AM Re: trim length [Re: garyrapp55]
ChadTRG42 Online   happy
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Registered: 09/16/09
Posts: 12221
Loc: Lewisville, TX
Originally Posted By: garyrapp55
So for 308 anything between 2.005-2.015 is good to go, or should there be a maximum accepted variation?


308 Win has a "book" max of 2.015" case length. I have let my personal 308 ammo go to 2.025" and load it and shoot it. It will still chamber and shoot good. But after about .010" longer than max length, you will run into chambering issues/problems. If the brass is too long, then when chambering, you essentially are squeezing the case mouth at the chamber and acting like a self crimp inside the chamber. This would be bad and cause some issues.

If you want to keep everything consistent, then you can trim them to all the same length (2.005"). For even my competition ammo, I will have some variance in the case neck lengths, and I don't really care that there is a slight variation. A consistent powder charge and bullet seating depth are the most important to me. I'm not worried about a .005" variation in case length, as long as I'm under the max length. But if it's over the max length by .010" or more, I'll start to worry and trim them back.
_________________________

Custom and Precision Ammunition!!
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Type 01 and Type 06 FFL

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#7051135 - 01/24/18 10:07 AM Re: trim length [Re: redchevy]
ChadTRG42 Online   happy
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Registered: 09/16/09
Posts: 12221
Loc: Lewisville, TX
Originally Posted By: redchevy
Would it matter what they are for? I wouldn't worry about it for uncrimped ammo, but is that enough variation to give you any issues with calibers that head space off of the case mouth like 9mm etc.? or enough variation to mess with crimping/roll crimping? If I'm crimping I always trim cases.


Yes, it would matter. If you roll crimp (like for a bottlenecked round, 308, 223, etc), a varying case length will cause varying amounts of crimp, which will effect your pressures from round to round, and will have inconsistent ammo. If you have a round like the 9mm or 40 cal that head space off the case mouth, I taper crimp these. This will still crimp but allow less variation from round to round with a varying case length. I load tons of mixed head stamp brass for 40 cal for my personal ammo. I don't worry about case length and crimping since I taper crimp them.

I use a Lee crimp die that squeezes the neck for a crimp, which will allow for a varying case neck length and not have a big issue with varying crimp tension. So, I change up what crimp method I use to account for the variations.
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Custom and Precision Ammunition!!
www.DallasReloads.com
Type 01 and Type 06 FFL

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#7051167 - 01/24/18 10:20 AM Re: trim length [Re: ChadTRG42]
garyrapp55 Offline
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Registered: 12/26/11
Posts: 528
Loc: Ft. Worth
Originally Posted By: ChadTRG42
Originally Posted By: garyrapp55
So for 308 anything between 2.005-2.015 is good to go, or should there be a maximum accepted variation?


308 Win has a "book" max of 2.015" case length. I have let my personal 308 ammo go to 2.025" and load it and shoot it. It will still chamber and shoot good. But after about .010" longer than max length, you will run into chambering issues/problems. If the brass is too long, then when chambering, you essentially are squeezing the case mouth at the chamber and acting like a self crimp inside the chamber. This would be bad and cause some issues.

If you want to keep everything consistent, then you can trim them to all the same length (2.005"). For even my competition ammo, I will have some variance in the case neck lengths, and I don't really care that there is a slight variation. A consistent powder charge and bullet seating depth are the most important to me. I'm not worried about a .005" variation in case length, as long as I'm under the max length. But if it's over the max length by .010" or more, I'll start to worry and trim them back.


Thanks for the advise. I'll keep em all between 2.005-2.015 and accept a max variation of .01"

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