I am setting up to do my first .223/ 5.56 reloads.  I noticed that the book shows a case length of 1.760.  I have looked at the data reference and I noticed that some people are using a case length of 1.74x or 1.75x.  Is the 1.760 a maximum length?  Is there a minimum length?  



What are some advantages of the different case lengths?  My trimmer trims the cases to 1.745 most of the time.  I have only trimmed about 15 cases so far.



Any wisdom is appreciated.  Thanks.

1.760 is max case length.  IIRC, 1.740 is minimum.  Myself and the vast majority trim to 1.750

I trim to 1.75 to 1.74 and set my COAL to 2.26 (mag length). I don't go shorter than 1.740.

Thanks.  I'll go ahead and continue the process at 1.745

1.730" is the minimum but the "recommended" trim length is 1.750"

Most people stay around the recommended trim length.

You are good at 1.745" At that length you will probably not have to trim before your next reloading. Maybe even 2 or 3.

If you are roll crimping though you will want them all the same length.

1.749?

Did you mean to post this?  Is this the minimum length that could be loaded?



 

Watch "Sinclair Chamber Length Gauge" on YouTube
Sinclair Chamber Length Gauge: http://youtu.be/JKnXJxaAw2U
I set my Giraud for 1.755"
1.749" wouldn't worry me but 1.745" might til I shot it with no ill effect.

Some brass (like federal .223) can consistently come out to less than 1.750 after sizing....I trim these to 1.740.  Because it's common and fairly consistent, I make a load around that case and pretty much use all those fc cases for 55gr fmj blasters. Even though they're cheap and somewhat short, they shoot really well from my bcms.  

Most 5.56 cases (LC, Pmc/psd, Winchester) is over 1.750 after sizing and gets trimmed to 1.750. I use those for all my other loads.

Why? What possible ill effect could there be? SAMMI says 1.730" is the minimum that means 1.745" is dead center in the tolerance or "nominal".

Set your caliper to .030" and look at the cap. Do you really think a band of brass .030" wide is going to make a significant difference. And you are only talking about .010" difference.

That's the line I draw for me. It hardly ever happens. You draw yours. That's whats nice about reloading your own ammo. You can do it any way you want.

Seems like every now and then someone post asking about case length cause they have the 1.750 number stuck in thier head  and they just measured some Factory once shot they had and it's around 1.740

Any other SAMMI specs folks want to call BS on ?

Not tracking.  



In my particular case, I have never reloaded a rifle round and the process is a lot different than pistol and shotgun.  When I looked at every book I have, they all have the 1.760 measurement.  When I went to this:  http://www.ar15.com/forums/t_6_42/342957_AR15_com_Reference_for__223_Remington_Load_Data.html



I found several postings on shorter case lengths being used.  I'm not sure what the comment about SAMMI soecs BS is about, but I would be interested in know what is the issue.



Thanks



 

I would have to throw away a lot of cases if I went with 1.750 minimum. RCBS-X die recommends 1.740 trim length. I hold 1 MOA out to 300 yds with no problem. After 5 loadings cases are 1.740-1.745. I should note that I don't load to max as I shoot for accuracy.

I have had factory Federal brass that was right at 1.740" and while I try to keep mine at 1.750" if a 1.745" piece appears I still use it as .005" just isn't enough to concern me.

I still trim my brass after every firing using my Giraud even when using the X-Die just because it doesn't take much effort.

RCBS-X die works for me. Initial trim to 1.74 (per RCBS instructions), after five reloadings and firing PMC, LC- lengths check 1.740-1.745. No split necks, etc. Note that I generally load to 2650 - 2800 fps (55 - 75 gr).

Something else to consider imo if you like trimming "short"......

Let's say you have a store bought round.  Lets say the brass measures 1.755.....and let's assume the brass is sized to minimum headspace specs so the manufacturer is confident it will "fit in most guns".  This is not a stretch to assume.

Now... assume we shoot the rounds in our AR and go to resize the case.   Many of us are not going to size back to minimum headspace.....we are going to bump the shoulder the way we want to (and end up with a piece of sized brass with more headspace than the store bought was more than likely.

Now...let's trim one of the sized cases sized for our rifle back to 1.755.     What got trimmed?     I say the neck did.

Now....let's trim another one of the sized cases back to 1.745.    What got trimmed?   I say the neck did.

Now.....let's say you could stand all three cases side by side and look at them.   The store bought case, the custom sized/trimmed to 1.755, and the custom sized/trimmed to 1.745.

It will be very noticeable how much shorter the neck is on the sized cases.......because all of the length we added to our headspace came out of the neck in the one we sized to the same length + an additional amount in the one we shortened.

I am of the camp that I don't want my necks that short......I tend to agree with dryflash that it's easier to control neck tension with a longer neck .... and I also like not reducing my necks that much, particularly  if I am loading light rounds (say 50 grain Zmax) to near mag length coals.....as there's theoretically not a lot of "extra" neck to give up at that point.   Why push it.

Only reason for this post is to make sure people are really thinking about what part of the brass is getting reduced the most when you combine more headspace with shorter trims.  

Just one mans opinion. ymmv  

EDA --- We should call them neck trimmers....not case trimmers

EDA2 --- I guess a guy could also look a the dimensions posted above and see what sammi says the neck length measurement should be too....and consider that as well

it's based upon SAAMI recommendations. 1.750 or 1.760 are both acceptable.  measure the case length for your chamber. It will probably be 1.780 or slightly greater. You can set you case length to around the case length of your chamber in e pinch.

AeroE, Where did you get that drawing?  I have also seen it as 1.760" -.030" I'm not nit picking in fact that was my point originally. We should not waist time nit picking over case length. For all practical purposes any case "in spec" will be fine to use. That is why they made the specifications in the first place.

There are many calibers that have much longer necks than needed. 30-30 is a prime example. Then on the other side we have the ,300 Win Mag that has a very short neck and this still works in semi auto rifles.

Some case lengths were made just to be different. A .357 Mag case is 1/10" longer than a 38spl. This was done simply so it could not be loaded into a 38spl revolver. It wasn't until later when powders like H-110 came out that the extra 1/10" of case could actually be used to hold a larger powder charge.

Did you happen to look up .223 Remington? It is 1.760" -.030" not -.020" like on the drawing you posted above.

Everyone should trim their brass as short as they like, that's what I always say, after all it's theirs.

I don't understand your question.  The drawing shown is for 223 Remington.  It shows 1.760" - 0.030".

I think a better question is this - where did you get your "-.020"?  What reference material can you site?


I searched online for a copy of the 5.56 NATO D-drawing but could not produce one.

I think the point of argument is that in the image AeroE posted, -.020" is listed (1.740" min):











But if you look up the diagram on the SAAMI website at the moment, it says -.030" (1.730" minimum).  Here is a grab from the PDF:









 

Which SAMMI specs are correct?  The .020 or .030?

The image I linked above that says -.030" is dated on the SAAMI website as drawn in March of 2001.





Unsure how old the image stating -.020" is, but it appears older based on the type of font used.  I believe SAAMI changes specifications from time to time for one reason or another?
So long as the brass isn't over the max length and still have enough neck to achieve enough neck tension you will be fine.  





Trim too much and you have less neck tension.  


Trim too little and you'll have to do more trimming and case prep between firings to keep it under max since the brass "grows" a bit when fired.





Find some happy middle ground that works for you and stick with it to maintain consistency.




As was said above:





 

The latest SAAMI-published information should be used - that's where I got the 0.030" tolerance I referenced from.

+1 I use the same trimmer and same 1.755 trim length.

I have been trimming to 1.750 with a Giraud trimmer, should I trim a little longer to increase the bearing surface of the neck on bullet due to the chamfer?

The link above is to the information Index.  Once there, click on "Chamber and Cartridge Drawing" under the Information and Specifications heading.


Here's a link to the Table of Contents of the Rifle cartridges and drawings.  It will launch a download of a PDF document.  Select the cartridge you are interested in and it will open up that page.

Link to Drawings

Yep, that's where I got my image above from.  You will have to use internet explorer per their homepage's instructions to open the caliber specific files.  It didn't work for me at first of firefox.