223 trimmed case length

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Lilswede1

New member
I am using the "worlds fastest trimmer" which fits on a drill.
Very fast but no matter how much I tinker with it I get a variation of 1.748" to 1.751" with the majority trimming to 1.750".
The trim is measured from the shoulder not from the base. When I measure a number of the fired cases with the Hornady Case Guage prior to trimming they all come out at 1.450" to 1.451". Very consistent.
Anyone else have the same problem?
I get kinda annal when reloading, consistency creates accuracy, is what I have read in here and I believe it.
 
Anyone else have the same problem?
Click to expand...

What's the problem?

I use the same trimmer for my .223. I have "set" it to 1.750" - or as close as I can get it. My final trim length is typically 1.749 to 1.753-ish. Four thousandths variation is plenty good for what we're doing here.

Time to move on and tackle the next problem.
 
Re Nick C S,
Likewise, trying to trim '06 brass to 2.484 with a Forster trimmer will drive you up the wall if you're thinking about getting that trim length every time. No problem if you are getting plus or minus .001 or so from the desired length. Don't measure every one after trimming in order to maintain your sanity.
 
So .002 from head to datum and the trimmer .003 . ? You're only really seeing a variance of .001 that's pretty good and that difference is likely because the trimmer is indexing on a different point on the shoulder then the Hornady gauge . As Nick said time to move on to bigger and more important things :)
 
Lilswede1,

The shoulder is what the case headspaces on to stop the neck going forward. You want to measure from the head to the shoulder and then from the head to the ogive of your seated bullets and see how consistent the difference between those two numbers is. This will tell you how consistently your bullets will be spaced from the throat. Measuring from the head is done because it is easy, but it's not the best measurement.
 
I use a Forster case trimmer. I set it to trim 223 brass to 1.753.

The non-standard trim length is due to the fact that I know how much (on average) my loading stretches my brass and I know how many loadings I can count on before my brass is "lost in the weeds" and I know that if I trim to 1.753, the brass will be lost before it needs to be trimmed again and trimming to 1.753 rather than 1.750 saves a lot of turns on the old Forster crank.

My caliper reads to the nearest 1/1000 and has a fifth digit that reads "5" or gives no indication. Once the trimmer is set up, I only sample the trimmed cases to make sure of the adjustment (like condor bravo suggests) and my trimmed brass reads 1.753 with that extraneous "5" occasionally appearing, so I assume I'm within my target +/- 1/1000 inch.

My rule is that if the bullet has a cannelure, crimp into it. If it doesn't, then don't crimp. With no crimp any length between 1.750 and 1.760 is fine.

But keep in mind that if a crimp is not being used, the only thing holding the bullet in place is the friction between the bullet and the neck, so trimming below 1.750 starts to reduce how tightly the bullet is held - not much for each 1/1000, but it adds up - so if you are routinely ending up shorter than 1.750, it might be advisable to set the target length a little longer so that the bottom end of the range is still at or above minimum.
 
I have an old Lyman trimmer that I made a set of bushings for. I never have to make any adjustments. I just put the correct bushing on the shaft and start trimming. It trims off the base so all my cases are the same length. I use it to check the length of the cases too because it takes less time than reading a caliper after getting a good bite. I run all my cases through the trimmer whether they need trimming or not. The ones that trim needed it and the ones that don't trim I know are in spec. One of these days I will take a picture of my setup.
 
Thank everyone for their responses. I sorted the finished brass and out of 500, 380 measured 1.750" and the rest (120) were within .002" below that. I will keep them separate when reloading and see if there is any difference at the shooting range in my guns. Just like the peace of mind that consistency gives me.
 
I use the same trimmer and get the same results in 223, but Im loading for volume. In the three guns I run this ammo in the accuracy is perfectly acceptable. But then Im not sitting at a bench trying to get itty bitty groups.

"Worlds fastest" and most accurate aren't exactly mutual. But you knew that. Guess the guestion is how accurate are you trying to be?
 
Your range is .003"? Do you know how small that is? +/- .0015" variation. This much variation can take place bu just the way you hold the case or how much pressure is applied or even how you hold your tongue while trimming...
 
"...from head to datum...The trim is measured from the shoulder..." NO!. Case lengths are measured from the case mouth to the end of the case.
The Hornady Case Gauge doesn't measure anything. It's a Go/No-Go gauge.
 
Im sure you probably won't believe me, but +/- .0015 variation in .223, especially being fired from an AR is negligible, and wont make any measurable difference. The other thing is, are you checking before or after you chamfer and deburr? Because burrs can mess up your measurements.

I use an RCBS 3 way cutter head on a trim pro 2 chucked up into a drill which cuts, chamfers, and deburrs all at once. With a 1.749" target I get 1.748-1.750" cut across 3500 rounds. If I use a standard head, I have to chamfer and deburr before measuring, otherwise there is much more variability.
 
T.O'heir. He's saying with that particular trimmer it works by putting the case in the trimmer, the trimmer stop on the shoulder of the case and the neck is trimmed from there.
 
What you are getting is within the limits of the device and its more than good enough.

Try that on a RCBS trimmer with the clamp setup, far worse and inconsistent.
 
I'm with T O'Heir . I have been using the RCBS Trim Pro , the older model with the shell plate , its giving me very accurate trimmed cases . Probably because I trim every firing , very little is shaved off with no resistance . I'm not in a rush I just want accurate measurements , never skip a step in peeping. Once the case is sized to the same dimension the case is trimmed . Measurement is from the head ( base of the case) to the end of the case neck . datum is for case headspace , base to datum . Once that is the same then you can trim to the exact case length. I set my trim length in the middle between the minimum & maximum ,works well for me.
 
Incidentally, the current SAAMI standard (2015) for .223 has changed since the previous on (1992 standard). In the older standard, the case length was 1.760" -0.020", so a case could be anywhere from 1.740"-1.760", and the middle value was 1.750", the middle value being what most folks use for trim-to length. The 2015 standard changed that to 1.760"-0.030", so 1.730"-1.760" is the current range and the new middle value is 1.745", which should, by tradition, be the new trim-too length. However, I don't see any load manuals jumping to change this, and I certainly am not going to both to change what I do with it.
 
Unclenick
Thank you , I wasn't aware of the change. I thought it was 1.750 - 60 what do you think the reasoning is for a .030 of trim range in stead of .020
 
Doesn't matter. As long as you trim to a consistent minimum you are good. 1.750 is as good as 1.745 - if its .003 off one way or the other its zero issue.

There is nothing magic about it, as long as the leading edge of the case does not get into the throat on the long end.
 
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