Shortest Safe Trim Length for .223?

[Homerboy]

I just got into reloading for rifle and am starting with .223. I know the books say trim to 1.75" with max length of 1.76". I also know many trim to shorter to maximize time between trimmings. So I set my trimmer to 1.745" and will go as high as 1.752". Some of them are coming in at 1.743" or so and I let them pass. The tiniest tremor or movement will change the reading by 1 thousanth of an inch or so so I just leave it.

But brass below 1.742" I am throwing into a "too short bucket".

I have read that SAAMI specs allow the case to go as low as 1.730". I'm not interested in going quite that low but I figure if I can safely use a shorter case then I will get more re-loadings between them before I need to trim again.

I'm going to use 27 grains of CFE 223 powder and a 55 grain FMJ bullet. I'm loading just above minimum. Just looking to make plinking ammo.

Opinions? Thanks.

 

[mrawesome22-250]

SAAMI spec is 1.760" - .030"

So 1.730" through 1.760", and anywhere in between, is within specifications.

https://saami.org/technical-information/cartridge-chamber-drawings/

 

[Slamfire]

Trim length is safety critical when cases are over maximum. You do not want the case neck jammed in the throat of the rifle chamber. That will pinch the case neck and raise pressures. Back in the day when I had hand trimmers and vernier calipers, (before cheap dial calipers), it took forever to trim and read the vernier measurements. So, I made a simplifying assumption: first time fired cases had to be fine. Well, I was wrong. New cases fired for the first time grow longer than any other firing period, they are always over max trim length. It took one box of reloads, all with blown primers, to figure out I needed to trim each time I sized a case.

There is no need to be concerned about trimming under some published trim length. Don't worry about it. As long as the case neck holds the bullet, pressures will be normal, the bullet will go out the barrel, and I am going to say, with a hand held rifle, you are not going to see anything on target! I regularly over trim cases setting up my powered trimmers, and I mean by a lot, and those cases go in the same pile as the "correctly" trimmed cases. And I don't have a problem on target.

Notice how much clearance between the case neck and the "throat". This gage was cut with a SAAMI minimum reamer. I trim these Garand cases at minimum, and often, they are below minimum. They function fine.

 

[Homerboy]

Thanks. I’m pretty OCD about reloading. Still weigh every charge and measure every case after a trim. So as long as I’m 1.730 or above I’m fine. I’m still gonna measure today be sure it’s under 1.760 but since the trimmer is set to about 1.745 I won’t be going over.

By the way, I’m using the Frankford Arsenal case prep center. Very handy once it’s all set up.

thanks for the help. Any other opinions always welcome!

 

[edwardware]

Well, if you get much below 1.560, you'll run out of neck.

If you're not crimping, I don't think there's any such thing as 'too short' within reason. If you are crimping, consistency will be your first issue.

 

[Homerboy]

Well, if you get much below 1.560, you'll run out of neck.

If you're not crimping, I don't think there's any such thing as 'too short' within reason. If you are crimping, consistency will be your first issue.

that’s another question. I crimp my pistol ammo and the die set I got came with the factory crimp die. I was planning on lightly crimping. Just don’t see why I shouldn’t. I know people say it’s not necessary but I just feel making sure the bullet doesn’t set back would be the right thing to do.

but would a case length of 1.740 matter if another was 1.745 regarding a crimp?

 

[edwardware]

. . . I just feel making sure the bullet doesn’t set back would be the right thing to do.

but would a case length of 1.740 matter if another was 1.745 regarding a crimp?

Two points:
1) You probably can't crimp enough to make up for insufficient neck tension. With sufficient neck tension, you won't experience setback.
2) All crimp dies excluding the Lee FCD are extraordinarily sensitive to trim length; you probably need to trim every time to achieve consistency.

 

[Homerboy]

Two points:
1) You probably can't crimp enough to make up for insufficient neck tension. With sufficient neck tension, you won't experience setback.
2) All crimp dies excluding the Lee FCD are extraordinarily sensitive to trim length; you probably need to trim every time to achieve consistency.

Thanks. New to this aspect of reloading. I’m using the lee factory crimp die. I’m also used to expanding the case mouths on pistol ammo but don’t have an expanding die for the rifle. So how can I make sure there’s enough neck tension?

 

[PWC]

Bear with me for a minute.....most non-repeated measurements are bad equipment or improper process. Take one case, make sure it is inside and outside chamfered (no burrs), measure at 3 different points. Open caliper and repeat measurement; should be the same.

Teaching quality inspectors how to get repeatable measurements to 10 thousanths is the hardest part of the job.

 

[edwardware]

I’m using the lee factory crimp die. How can I make sure there’s enough neck tension?

Your Lee FL sizer should produce plenty of tension; it's not adjustable with your equipment, so not an issue.

 

[Walkalong]

repeatable measurements to 10 thousanths

Yea, the nearest .0001 repeatedly take practice, no doubt, good thing most reloading doesn't require that.

 

[Homerboy]

Yea, the nearest .0001 repeatedly take practice, no doubt, good thing most reloading doesn't require that.

Not to mention a caliper that a NASA scientist would use. I have a Hornady digital one. .0001” is easy to miss.

 

[edwardware]

Teaching quality inspectors how to get repeatable measurements to 10 thousanths is the hardest part of the job.

Yea, the nearest .0001 repeatedly takes practice. . .

Ten thousandths =0.010. You should be repeatable in that range with a quality vernier caliper and good technique.

A tenth of a thousandth =0.0001, two whole orders smaller. With really a really good micrometer you can imagine that you're repeatable, but outside of a temp controlled metrology lab you're kidding yourself. Your hands warming the tools and the subject matter will spoil that.

 

[PWC]

The point is, the surface area of most of what we measure is small and it is easy to mis-measure. Unless you do it all the time, even .XXX is easy to miss, and in reloading, that is sufficient. Of you do gunsmithing, then you need .XXXX, which is withon the capability of most digital calipers.

 

[Walkalong]

Ten thousandths =0.010. You should be repeatable in that range with a quality vernier caliper and good technique.

A tenth of a thousandth =0.0001, two whole orders smaller. With really a really good micrometer you can imagine that you're repeatable, but outside of a temp controlled metrology lab you're kidding yourself. Your hands warming the tools and the subject matter will spoil that.

Dang, I sure read that one wrong. Yep, ten thousandths, .010, isn't hard, .0001, is, much. .

 

[cougar1717]

I know the books say trim to 1.75"

So I set my trimmer to 1.745"

I know people say it’s not necessary but I just feel making sure the bullet doesn’t set back would be the right thing to do.

So the logic goes: OP knows what the minimum trim length is and chooses to set it lower in an attempt to reduce the number of successive trimmings.
This cuts down the neck that you need for bullet tension, but OP wants to make up for the lack of neck tension with crimp to reduce the chance of bullet setback.

It all starts at the beginning. If a reloader sets the trim length to 1.750", there will be a few that are under and a few over, but the majority will be +/- .003" typically. OP's logic for cutting short necks is to save trimming time. The problem is that IME, once fired 223/556 brass is going to grow over 0.010" (even 0.015" with some thick mil brass) on the first sizing and somewhere between 0.005" and 0.007" on the second sizing. Successive sizings grow the brass much less since there is less brass to flow up to the neck. (Case growth does depend on brass and sizing die and I'm sure someone is about to gloat about their RCBS X die in 3...2...1...)

The point is that whether you cut them to 1.750" or a little shorter than that, over the lifetime of 5-6 firings, the reloader is going to cut them at least twice and measure them all after sizing #2 through the firing where the neck splits. This assumes that after sizing #1 that they all need trimming. So cutting them to 1.742" most likely necessitates trimming on sizing #1 and #3 instead of sizing #1 and #2 when cut to 1.750". So what is the difference? Except maybe that loading #2 didn't have chamfered case mouths.

 

[TonyAngel]

When loading for an AR, I want to do it fast because I’m gonna need a lot of it. I use a powder dropper with ball powder. No need to weigh each charge.

As long as you don’t go over the maximum length, you’ll be fine. All of your loaded rounds will be the same length anyway.

Use the Lee fcd. It doesn’t care about length and a few thousandths here or there won’t matter. I use a medium crimp and haven’t had problems in 15 years. If you’re loading for a bolt gun, neck tension should be sufficient and you shouldn’t need to crimp.

If your gonna use a minimum charge weight, loss a few and try them first. If these are for an AR you’ll wanna make sure they will cycle the rifle. Really, all fmj .223 is plinking ammo. Why load so light. If you want light, shoot a .22. Not being a smart ass, it’s just that loading puff loads costs the same as full power loads and even full power loads aren’t all that.