How fussy do I have to be about trimming brass? I'm not sure what to do.

[zippygaloo]

I'm loading for my AR15. How fussy do I have to be about trimming brass? I've got a bunch of .223/5.56mm cases and want to reload them, but I'm not sure exactly what I need to do in terms of trimming. I know max case length for .223 is 1.760 inches and that this length should not be exceeded, but I'm not sure as to what length I SHOULD trim them.

This is what I'm doing right now, please let me know if it's not correct. Because I want a consistent crimp I'm trimming everything in batches to the same length. For instance, when measuring my cases before trimming, some come in at or around 1.752 inches, some at or around 1.749 inches, etc. So I've been trimming a batch of 20 of the at or around 1.752 inches all down to 1.751 inches and the at or around 1.749 inches all down to 1.748 inches. Also, sometimes (after trimming) the digital caliper numbers jump a bit when measuring the case, say from 1.7485 inches to 1.749 inches (or even 1.750) and then to 1.748 inches. What do I call that case length? How precise should I expect my measurment to be?

Is this how I should be doing it? Or am I doing something wrong? How fussy do I have to be about trimming brass? Would I be better off just setting my calipers to 1.760 inches and just make sure everything fits and then be good to go?

Also, what is the minimum case length for .223/5.56mm?

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[motoman98]

Usual trim length on bottle neck cases is .010 in under maximum listed. Bullet seating: my preference is the taper crimp, you don't have to worry about being dead on length for a whole "lot", which is a pain and can produce rejects from variables. BTW: Dillon's seating die for the .223 is a taper crimp!

 

[millwrt52]

For an ar, I trim to 1.750 +/- .002 or so. If you'd use a Lee Factory Crimp Die, the length isn't as critical.

 

[zippygaloo]

For an ar, I trim to 1.750 +/- .002 or so. If you'd use a Lee Factory Crimp Die, the length isn't as critical.

So what would you do with the cases that measure 1.748 inches from the start?

 

[civilian75]

So what would you do with the cases that measure 1.748 inches from the start?

I'd say that fall under the 1.750 +/- .002

 

[millwrt52]

Yep, just load 'em up.

 

[deadshot2]

The purpose of trimming .223 ammo for an AR is two-fold. One is to make sure the case isn't too long for the chamber (neck portion) so it doesn't "trap" the bullet and cause high pressures. The other is to provide for a uniform crimp into the cannelure on FMJ-BT Military type bullets.

I set my trimmer to 1.750 so the brass doesn't need to be trimmed every loading. If I hand check case length I just lock my caliper at 1.755" and check each case. The ones that pass through go into the "No Trim" bucket and those that don't go into the "Trim" bucket.

Unless the case is too short to provide adequate "hold" for a bullet, don't sweat the cases that are a few thousandths too short. Shoot them a couple of times and they'll grow

 

[Jamie6.5]

I set my trimmer to 1.750 so the brass doesn't need to be trimmed every loading. If I hand check case length I just lock my caliper at 1.755" and check each case. The ones that pass through go into the "No Trim" bucket and those that don't go into the "Trim" bucket.

Yup.
That's the Go or No-Go method.
I use it too. It works great.

Be sure you do it AFTER resizing though.

 

[ma96782]

Besides getting a uniform crimp, do you know why trimming is important?

Some reading for you (The answer is about half way down the page. But, I suggest that you read all of it.).........

Internal Ballistics - Hornady Manufacturing, Inc

More advice........

Since you're loading for a semi auto it's really important to have consistent ammo. So, if you haven't already gotten a case gauge, I strongly suggest that you invest in one. It'll help with checking your reloads.

Use A Case Gauge-- Use a case gauge as sold by L. E. Wilson and Dillon to set up your sizing die. This insures that your headspace will be correct and consistent. If a case dropped into the die has its rim between the high and low steps on the gauge your die is properly set.

What does a typical case gauge look like?

Miscellaneous Questions

Aloha, Mark

PS....my case gauge also doubles as a trim length gauge.

 

[Spitpatch]

As with most of my life and advice from that source, Im with Ma.

Caveat: I am NOT a volume reloader. I am a handloader. I am also not a "stump shooter" or "noise maker". Some of the lay-say-fare and cavalier attitudes stated here may serve stump shooters and noise makers very well.

Case length is critical for reliability (especially in a semi-auto firearm) and accuracy. In a semi-auto gun, it can become essential. (And, of course, you can ignore it for a time, and suffer a malfunction somewhere along the line in your stump-shooting, noise making pursuits: to no serious detriment at all).

The greatest imptetus toward consistent case-length in a semi-auto gun (and revolvers are just as picky), is where the crimp will happen and how consistent is it when it happens? In any round crimped, consistency in the crimp is essential to accuracy, and can very quickly become essential to mechanical operation of the gun.

I DO NOT crimp handloads for my AR. Never saw the need. Would not disparage or argue with anyone that does. Even without crimping concerns there, I trim (as I do EVERYTHING IN ANY CARTRIDGE, BUFFALO GUN TO .25 AUTO) consistently. Gives me consistent grip on the bullet, consistent placement of the case in the chamber, and avoids a wealth (poverty?) of other concerns.

With centerfire rifles, you will find that if you trim to the "trim-to" length at first loading, you will enjoy exemption for quite some time, and all your brass that is fired with the same load will amazingly only lengthen to nearly precisely equal amounts with each loading and firing.

 

[deadshot2]

Case length is critical for reliability (especially in a semi-auto firearm) and accuracy.

There was a recent discussion on the accurate shooters forum regarding trimming. The general consensus among the true accuracy experts was that everyone pretty much "over trims" their cases. Trimming should only be done to make sure the case isn't too long for the chamber. If one isn't crimping, as long as the case allows the bolt to go to battery it's short enough. Of course these are the guys that have rooms full of trophies earned by their skills so what do they know

BTW, go to a Bench Rest match and watch the top shooters. They'll use the same 5 cases all day long, reloading them with a quick scrape of the primer pocket and a brush out of the neck. That's pretty much all the case prep other than neck sizing that they do.

 

[Spitpatch]

I agree. No need to trim,trim,trim everytime to get back to "trim-to" length. Once you have achieved length uniformity in that lot of cases, firing with similar loads will maintain that uniformity (perhaps for the life of the case: my mentioned "exemption"). This is what is in play (as you mentioned) at the benchrest circuit. Shooters who load always at the top end, full length resize every time (perhaps for a pump or auto gun), or deal with a "springy" action (such as a Savage 99) may not enjoy the exemption for quite as long as someone able to get away with only necksizing.

I would differ with a statement that "trimming should ONLY be done to make sure the case isn't too long for the chamber". Trimming is also done (at least by me, and anyone interested in uniformity) to achieve equal tension (and equal release) of the bullet in the neck, from case to case in the same lot. I sincerely doubt any benchrester would completely ignore case length from the outset in a given lot of cases. He begins by insisting on uniform case length at the start, and then probably need not worry again.

 

[Gunner3456]

Lots of good info here. I always trim a new-to-me batch, but I'm actually using my trimmer to measure. There is a danger in a case that's too long, and there is a need for consistent crimps.

One thing. I once bought a batch of bullets which weren't as pointed as I was used to. I trimmed and loaded them, getting the crimp nicely in the cannelure. Fortunately after just a few, I measured overall length and then chambered a couple. The bullets stuck in the lands. Bad, bad news.

So, there's a lot more to it than just case length. I now try to stay with the same brand and type of bullet for FMJ, and another for PSP, and I've found those which are just about the same shape and I'm good.

 

[deadshot2]

He begins by insisting on uniform case length at the start, and then probably need not worry again.

Because they usually only neck size. Proper expanding of the sized case, neck or F/L plays a far bigger role in uniform neck tension rather than a few thousandth's variation in neck length.

 

[Spitpatch]

Right.Precise sizing of the neck is a greater factor in uniform neck tension rather than a few thousandth's variation in neck length. But that few thousandth's IS a factor that can easily be controlled, and therefore we do.

 

[mookmanjdj]

Lots of intelligent information here. Thanks to all the experienced loaders on this site.

 

[deadshot2]

Right.Precise sizing of the neck is a greater factor in uniform neck tension rather than a few thousandth's variation in neck length. But that few thousandth's IS a factor that can easily be controlled, and therefore we do.

Do you measure your bullet lengths? Base to Ogive? OAL?

A bullet can have a wide variation of base to ogive lengths and since most seating dies use the ogive to press the bullet into the case, you can have a wide variation in seating depth. This is again another of those factors that can have more effect than a few thousandths difference in case length.

Basically, there are other factors that have a lot MORE effect on bullet performance than being anal over the length of the case neck. In a rifle that kicks the bullet out of the case at pressures approaching 60,000 PSI (62,000 psi for .308), I would concentrate more on those factors that cause these pressures to vary immensely. Seating depth, free bore, neck tension are primaries. Variations of bearing surface in the bullet also is a major factor.

Trimming for my .308 cases has become a task that gets done when I anneal. Not after every firing. Most of my brass doesn't get a full prep until after I've fired it a couple times. Size, neck trim, anneal, tumble in SS media, expand, load. From then on it just gets reloaded. Must be OK. I've got a target I'm going to try and duplicate this morning the range. Is a "teener" with the 5 round group measuring .191". Expect little or no wind today so I'll be happy if I can at least meet that group size, maybe even make a smaller one.

BTW, this is a "Factory" Remington 700 with 5-R Milspec barrel. Almost as much freebore as a Weatherby, several thousand rounds through the barrel, and still shoots great.

 

[Spitpatch]

Don't measure the bullets, because it is not something I can change, except by culling.

I trim to precise length because it is something I can easily do, costs no money (like culling), and results in eliminating (easily) one more variable. We are in agreement that trimming is NOT done each and every time a case is loaded, and my practice is to trim to precise identical length on new brass, and not give it another (anal or otherwise) thought (aside from checking it through random sample) usually for the life of the case (unless as mentioned previously, the brass lot is fired with different loads, or in a gun that cultivates case stretching).

 

[deadshot2]

Don't measure the bullets, because it is not something I can change, except by culling.

One does not have to "cull". I merely "segregate" bullets of similar length, base to ogive. That way I can make sure that the "jump" and "insertion depth" is uniform. Not so concerned that it's not exactly the same from batch to batch as much as I am concerned that it is uniform from shot to shot within the batch. First shot will show any variation in speed (if enough) that might effect impact point. I never toss out a bullet, even the few I encounter that looks like it was finished in a Hershey Kiss wrapping machine with a twist marks in the jacket

 

[millwrt52]

I think this thread morphed from a AR reloading type question to Precision Rifle reloading.