The book says max length for an empty cartridge case should be 1.76 inches and the trim length should be 1.75. I just went through over 400 cases and trimmed them all to 1.75. My question is, have you seen much difference in accuracy when loading cases that are only .01" difference in length? Some of the cases we're 1.76, but I trimmed all of them. Thoughts?
Trim length for .223?
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Reloadron
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The normal suggested trim length for 223 Remington is 1.750" as you mentioned with a Max case length of 1.760". Looking at the SAAMI specification the Max case length is 1.760" - .030" so the case length range is between 1.730" to 1.760".
As to accuracy? The idea is uniformity. I try to keep all my cases within spec and make them all the same as in uniform. The idea being that since we load to a COL with the bullet in place a longer case will tend to have maybe more neck tension than a shorter case. I just want uniformity when loading accurate ammunition. You want to control as many variables as possible.
How much will it matter? Likely not very much if some are 1.760" and some are 1.750". I just avoid it.
Ron
As to accuracy? The idea is uniformity. I try to keep all my cases within spec and make them all the same as in uniform. The idea being that since we load to a COL with the bullet in place a longer case will tend to have maybe more neck tension than a shorter case. I just want uniformity when loading accurate ammunition. You want to control as many variables as possible.
How much will it matter? Likely not very much if some are 1.760" and some are 1.750". I just avoid it.
Ron
ironworkerwill
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spitballer
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Even cases that are only neck-sized will eventually be rolled out lengthwise by the forward-moving pressure waves, and you can tell when it's gotten too long when the chamfer starts to curl up against the bottom of the bore. This is dangerous territory and cases must be trimmed for safety's sake at this point. But I agree with reloadron that consistency remains the key, so the question is probably "how much pressure is the trimmed case going to allow past the projectile before it seals in the barrel, as compared to the case before it is trimmed?". I can see your point, and the obvious next question is "does this mean I should avoid trimming the case any more than is absolutely necessary?". Maybe trimmed cases can be compensated for by adjusting the distance to the lands when seating or something. Maybe walkalong is right and we're worrying about stuff that's not worth worrying about. I do think that bullet runout is at least as important as the increased flow around the projectile from a trimmed case.
Thanks for the thoughtful responses. In the future, I'll plan to trim every time the case stretches even a little. My Lyman power trimmer makes it a manageable job. I trimmed all 423 cases!
You really do not have to but whatever makes you happy. I'll be glad to send you mine as I hate trimming plus deburring plus chamfering.
My neck sized only for bolt action do not require much trimming at all.
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