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Posted: 5/15/2010 3:49:07 PM EDT
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In my reading, it appears that max case length on fired 5.56 cases is 1.760. Trim to length is 1.750.
I am processing about 1K 1X cases of various makes, lots if LC. Couple questions. Why does the case length seem to vary so much on what is supposed to be 1x brass? (I can confirm a lot, but not all, are actually only fired once). I am getting readings everywhere from 1.5 to 1.75. I would think they would be more consistent. At any rate, I am resizing the brass and separating it between "ready to load" and needs a trip to Mr Giraud. Just curious about the size variance. Also wondering do you all actually trim all brass once it gets to or beyond 1.76" and do you all use 1.75 as your trim to length? Edited for missing 7's, LOL |
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Quoted:
In my reading, it appears that max case length on fired 5.56 cases is 1.760. Trim to length is 1.50. I am processing about 1K 1X cases of various makes, lots if LC. Couple questions. Why does the case length seem to vary so much on what is supposed to be 1x brass? (I can confirm a lot, but not all, are actually only fired once). I am getting readings everywhere from 1.5 to 1.75. I would think they would be more consistent. At any rate, I am resizing the brass and separating it between "ready to load" and needs a trip to Mr Giraud. Just curious about the size variance. Also wondering do you all actually trim all brass once it gets to or beyond 1.6" and do you all use 1.5 as your trim to length? Maximum length is 1.76 inches. Trim to length is 1.75 inches. If a case is 1.74, it's okay. The RCBS X Die is used with cases that start out at 1.74 inches and everyone that uses one reports the length doesn't grow. Uniform trim length is important if you plan to crimp. All the cases need to be the same length in order for the crimps to be identical. It's also important for one of those details needed to make perfect brass for precision shooting. I generally trim to about 1.753 to 1.755 inches, partly because I don't want to fiddle with a trimmer any more than necessary and partly because I want to preserve as much of the neck as possible for neck tension. If you think you want to let cases grow longer than 1.76 inches, then the chamber can be measured with a small stepped tool sold by Sinclair. But, if you want to use the ammo in more than one rifle, then every rifle has to be checked. Off the rack AR rifles generally allow this, but I would check any gun with a custom barrel as it will probably be closer to the SAAMI spec length in the neck part of the chamber. A case that is too long for the chamber will have the mouth trapped in the transition to the leade and cause an over pressure condition because the bullet can't be released. The cases you have will vary all over because they were likely fired in different guns. |
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Quoted:
In my reading, it appears that max case length on fired 5.56 cases is 1.760. Trim to length is 1.50. I am processing about 1K 1X cases of various makes, lots if LC. Couple questions. Why does the case length seem to vary so much on what is supposed to be 1x brass? (I can confirm a lot, but not all, are actually only fired once). I am getting readings everywhere from 1.5 to 1.75. I would think they would be more consistent. At any rate, I am resizing the brass and separating it between "ready to load" and needs a trip to Mr Giraud. Just curious about the size variance. Also wondering do you all actually trim all brass once it gets to or beyond 1.6" and do you all use 1.5 as your trim to length? "Once fired brass" may have been fired in a variety of guns with a variety of different charge weights. Some hot loads, some mild. That accounts for the difference on overall length of the brass. I try not to trim my used brass. After resizing, I set my calipers to 1.758"-1.759" Any brass over 1.759 gets trimmed. Under 1.759" doesn't get trimmed. Trimming your own brass back to 1.750 every time isn't necessary. Trimming only when needed extends the life of the brass. |
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I agree that the once-fired stuff you've got was probably shot out of different guns, hence the variation in length. Nothing to be concerned about though.
I also ONLY trim if they're longer than 1.760. And I don't get 'em all down to exactly 1.750, just as long as they're under that max length. |
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Brass from the same lot will be all over the place. It's a normal thing. Mixed years of LC, your brass is what I would expect.
Myself I trim every time. I just think it's the same amount of work/time to measure as it is to trim. Of course it all depends on your trimmer. |
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