AR case length

[agshooter]

So I know the reloading manuals say to cut case to 1.75 and not let them get longer than 1.760.

My LC brass that I once-fired myself are already over 1.760, mostly in the 1.762-8 range.

Some reloading reading I have done indicates you do not want to keep cutting to the 1.75 length, instead use the fired case to determine your case length and go from there?

I am surprised by the 1.760 limit if the once-fired is already over that?? What case length are y'all using (in general of course).

 

[suzukisam]

I use a factory crimp die and case length isn't near so much of an issue, of coarse your chamber type, 5.56/223/wylde ect makes a difference too. I usually trim to the trim-to length and then I fire them several times before re-trimming them. if they are a little over and they are chambering fine, I never worry too much about it.. even my FCD says in the paper work not to worry too much about case length...

 

[cfullgraf]

I made a "no-go" case length gauge for my 223 Remington. After resizing, if the case does not fit the gauge, it gets trimmed. I made it to measure a couple thousandths less than the trim length. A caliper would do the same but i have issues with using a precision instrument for frequent repetitive measurements.

My trimmer is set to trim cases a couple thousandths longer than the minimum so mu cases are within a range of about .006".

I trim about 30% or so of cases each time I resize.

No need to crimp for the AR-15 so uniform case length for crimping is not an issue.

 

[atblis]

You can also trim short (1.740" or so). By doing this, you generally will only have to trim once as the brass will fail or get lost before reaching 1.760".

Trimming can be important for crimping reasons which includes having the case mouth consistently line up with a cannelure for a given OAL. Otherwise as long as it isn't too long...meh who cares.

Get a Dillon XL650 with a Dillon rapid trimmer. No need to measure cases, they either get trimmed or they're under length. No need to measure anything.

 

[Cherokee]

I trim my brass to 1.75-1.755 after every firing. My Giraud trimmer makes it easy and I don't have to worry about my loaded ammo chambering is several different 5.56's.

 

[Waywatcher]

Some reloading reading I have done indicates you do not want to keep cutting to the 1.75 length, instead use the fired case to determine your case length and go from there?

I am surprised by the 1.760 limit if the once-fired is already over that?? What case length are y'all using (in general of course).

This may be true if you only neck size, but when we full length size brass, the sides get pushed inward and the shoulder gets pushed down. The forces on the brass are such that it lengthens the brass in the neck and it gets longer. Full length sizing, in my experience, necessitates case trimming.

The easy and simple rule I follow is: I spec my AR reloads to factory specs for headspace and length. I might not extract every last bit of accuracy available, sure, fine. But it is reliable and safe, which is more important to me.

 

[Cemetery21]

Unfortunately, some brass will exceed max length after one or two firing/resizing cycles. I've not heard that brass shouldn't be trimmed repeatedly. I normally get over 10 loadings from 223 brass and it may be trimmed 3 or more times. If you don't load hot and you necksize only, you can probably get more loadings and trim less.
Anyway, Sinclair makes a handy tool to measure the actual length of the chamber. That's one of the first things I do with a new rifle - record the actual max case length for that chamber. Then I know how far over 1.760" I can go before trimming (in most chambers, it's closer to 1.770"+)

 

[Walkalong]

So I know the reloading manuals say to cut case to 1.75 and not let them get longer than 1.760.

And that is what you should do. Nothing complicated about it.

 

[W.E.G.]

I normally get over 10 loadings from 223 brass

You might get that with brand new brass, and if you reload it repeatedly over a fairly short time, and if you don't shoot it in AR-15's.

Let that brass get old, or shoot it much in an AR-15, and you can expect head separations in enough of that batch of brass to make you want to re-think your longevity expectations.

 

[Walkalong]

I recently ran some velocity tests in an AR with a set of ten once fired (at least) .223 cases. LC, RP, FC. I sized them to fit a Wilson case gauge, trimming as needed. I scrapped a couple at around 7 firings for loose primer pockets. I scrapped a couple more at around 10 firings, and decided to scrap the rest after 12 or 13 firings due to the primers being very easy to insert, but they could have worked again. None showed any internal signs of case head separation.

 

[suzukisam]

Not much of my brass will ever see ten loadings, since i'd have to shoot 5,000 pieces ten times, and I pick up a lot of once fired everytime I shoot...but I wouldn't think that too impractical of an expectation, assuming not loaded too hot...I'm on my seventh load with some 300 weatherby mag cases and they still look good

 

[Clark]

I measure the chamber length to the end of the neck.
Then I subtract the difference between the case shoulder and the chamber shoulder.
I do that subtraction to compensate for the distance the firing pin pushes the case forward.

 

[chrome_austex]

Any brass over 1.76 gets trimmed to 1.75 or 1.745. Anything I accidentally trim much below 1.745 gets tossed.

I full length resize for my AR, so thats usually good for ~3 or so reloadings before I need to trim again.

I don't use a go/no-go gauge, but just use my dial calipers instead.

 

[Cemetery21]

Quote: Let that brass get old, or shoot it much in an AR-15, and you can expect head separations in enough of that batch of brass to make you want to re-think your longevity expectations.

Most of my 223 is shot in ARs. I don't remember a case head separation in over 25 years of loading for ARs. But, all of my shooting is in 20"-24" heavy stainless varmint barrels with tight 223 chambers and slow twists, built as bench guns for prairie dogs. I keep the brass separated for each rifle and the sizing die is set to push the shoulders back no more than necessary. And, I don't use a small base die. My brass failures come from split necks on brass loaded more than 10 times.

I realize my usage of 223s and ARs is not typical and my experiences probably should not be cited as examples.

 

[helotaxi]

I've had neck splits and two cases break in half, one in the die and the other as I was sliding it into the shell holder. Both of those were ragged breaks near the middle of the case instead of just ahead of the web like you would expect with a head separation.

None of my 3 ARs require a small base die to function well with reloads. It will shorten the brass life.

 

[steve4102]

Some reloading reading I have done indicates you do not want to keep cutting to the 1.75 length, instead use the fired case to determine your case length and go from there?

Were did you read this nonsense? You basically have already answered your own question. If it's over 1.760 trim it, if it is between 1.750 and 1.760 don't trim it. If you are going to use the crimp feature on your seating die trim all brass to the same length every time.