I'm ready to "trim to length" some LC 5.56 x 45mm Nato cases, but can't find any information on the interweb stating a minimum case length for this cartridge. My Speer reloading manual states a length of 1.76", but doesn't say if it is minimum or maximum length. When I put a sized/ de-primed case, that is currently 1.77", in my Dillon case gage; the neck protrudes out the end quite a bit. I'm thinking the stated case length, in the Speer manual, is maximum, but would like to know for sure... Any help greatly appreciated, but no guesses please!

This message has been edited. Last edited by: debwb,

See here:
http://saami.org/specification...AAMI_CFR.pdf#page=13

Maximum case length is 1.760" while recommended trim length is 1.750". You may run into some fired cases even slightly shorter than the trim length. At 1.750" trim length you should be able to reload a few times before they need trimming again.

Yep, 1.76 is trim at, 1.75 is trim to.

I have loaded brass that measured as short as 1.74 without so much as a second thought. There's no safety concern with it, perhaps some effect on accuracy. Since my straight .223 cases aren't a precision cartridge, I never worried about it.

*IF* you crimp, it is important that you have all the brass the same length or you'll get uneven crimp on the rounds you are loading, which will definitely cause accuracy issues, and if the brass is too far out of spec (the long way), could potentially end up unsafe if your crimp die is set for a shorter case.

Thanks to those that replied. Your knowledge and help is greatly appreciated; I'm good to go now!

I didn't test my page link and my pdf reader didn't update the link while I was scrolling to the correct SAAMI page, which is page 80 in the pdf and page 68 in the text copy.

http://saami.org/specification...AAMI_CFR.pdf#page=80

SAAMI's drwg shows the maximum length dimension as 1.76 inches with a (downside only) tolerance of -0.030 inches for cartridge manufacturers, i.e., 1.73" to 1.76". In reloading re-usage, other criteria may prevail. Please accept my apology.

Thanks for the update; I looked at the original link you sent me and it has some great information in it... The one thing that confuses me is in the bottom drawing (page 68) that shows several lengths beyond the 1.76" case length. I see 1,7720, 1.787, 1.812 and 1.8570 and have no idea what they are representing.

quote:

Originally posted by Orthogonal:
I didn't test my page link and my pdf reader didn't update the link while I was scrolling to the correct SAAMI page, which is page 80 in the pdf and page 68 in the text copy.

http://saami.org/specification...AAMI_CFR.pdf#page=80

SAAMI's drwg shows the maximum length dimension as 1.76 inches with a (downside only) tolerance of -0.030 inches for cartridge manufacturers, i.e., 1.73" to 1.76". In reloading re-usage, other criteria may prevail. Please accept my apology.

quote:

Originally posted by debwb:
Thanks for the update; I looked at the original link you sent me and it has some great information in it... The one thing that confuses me is in the bottom drawing (page 68) that shows several lengths beyond the 1.76" case length. I see 1,7720, 1.787, 1.812 and 1.8570 and have no idea what they are representing.

quote:

Originally posted by Orthogonal:
I didn't test my page link and my pdf reader didn't update the link while I was scrolling to the correct SAAMI page, which is page 80 in the pdf and page 68 in the text copy.

http://saami.org/specification...AAMI_CFR.pdf#page=80

SAAMI's drwg shows the maximum length dimension as 1.76 inches with a (downside only) tolerance of -0.030 inches for cartridge manufacturers, i.e., 1.73" to 1.76". In reloading re-usage, other criteria may prevail. Please accept my apology.

The top drawing is the one you want to be looking at.

The bottom drawing on page 68 is chamber dimensions, and for the purposes of trimming brass, they are irrelevant.

The numbers are for various specifications such as freebore and leade, and for the purposes of reloading "factory replacement" ammunition, can be ignored.

Thank you sir for the clarification. Knowledge is power and the folks here on Sig Forum seem to have plenty of it...

quote:

Originally posted by exx1976:

quote:

Originally posted by debwb:
Thanks for the update; I looked at the original link you sent me and it has some great information in it... The one thing that confuses me is in the bottom drawing (page 68) that shows several lengths beyond the 1.76" case length. I see 1,7720, 1.787, 1.812 and 1.8570 and have no idea what they are representing.

quote:

Originally posted by Orthogonal:
I didn't test my page link and my pdf reader didn't update the link while I was scrolling to the correct SAAMI page, which is page 80 in the pdf and page 68 in the text copy.

http://saami.org/specification...AAMI_CFR.pdf#page=80

SAAMI's drwg shows the maximum length dimension as 1.76 inches with a (downside only) tolerance of -0.030 inches for cartridge manufacturers, i.e., 1.73" to 1.76". In reloading re-usage, other criteria may prevail. Please accept my apology.

The top drawing is the one you want to be looking at.

The bottom drawing on page 68 is chamber dimensions, and for the purposes of trimming brass, they are irrelevant.

The numbers are for various specifications such as freebore and leade, and for the purposes of reloading "factory replacement" ammunition, can be ignored.

An interesting footnote perhaps.

This AM I ran across an older SAAMI, trimmed, drwg of the .223 Rem cartridge that I had a few years back pasted into a MS Word format. However the date box of that drwg was cut off. The date that I built that Word file was 2/7/2013 and much to my surprise the tolerance on the case length dimension of 1.76" was minus 0.020" i.e., not the current -0.030" !

The conclusion is that sometime in the intervening 4 years, for some unstated reason, the length tolerance has since been generously enlarged. Speculation might be that it was the common one, a cost savings for a mfr to be had with none to acceptable or inconsequential impact on the product's performance.