What qualifies as uniform case length?

[Comfy]

I measured some loaded .223 cartridges (with j-words) and discovered that most of the case lengths were at 1.750" +- 0.003" and a minority were as long as 1.757". These were all trimmed with the Frankford Arsenal Case Prep Center.

I wanted to see how this affected the crimp, so I then measured the OD of the case mouth and found that a 1.750" case measured 0.245" and a 1.757" case measured 0.244"

So I wonder... when you are looking for a uniform crimp, what kind of tolerance would be within the bounds of "uniform case lengths"? Does this expectation change as you do heavier crimps?

[trails4u]

If it's something I care about shooting 'accurately'....I don't mean benchrest, then .003 is well within my personal tolerances. Most stuff for plinking, targets, etc... If I'm within .010-.015 and not excessively long, I load it and shoot it. It just depends on what your purpose is for that given load...

I would find your load/tolerances and measurements well within my OK range for just about anything...

[country gent]

Tolerances are a part of manufacturing processes. Some thing to consider is your .003 +/- is .006 total variation.

I trim all new brass not just for size but to square the case mouths. Length is important for consistent crimp and release, But so is square as out of square also creates an uneven crimp around the bullet.

With most trimmers +/- .001 is obtainable fairly easily.

I have set up a trimmer to chamfer and deburr case mouths to get uniformity there also. It did cut down on unexplained fliers some. The more uniform the better but then only you can decide how far you want to go

[Dieselhorses]

Good question. Most manuals state "trim length" on .223 Remington to be 1.75" and max 1.76". When I add to my "stockpile" of .223 ammo I usually let anything from 1.74" to 1.755" go through the gate, but trimming LONGER than 1.755" for squareness. Doesn't interfere with any crimping I do because I have my FCD set up for a moderate crimp. So for cases right at 1.75" I follow through with entire travel of ram. Anything longer I can "feel" that extra length in my old Lee turret press and don't go quite the entire distance-but almost, taking care not to squish the pill.

[Three44s]

Tolerances are a part of manufacturing processes. Some thing to consider is your .003 +/- is .006 total variation.

I trim all new brass not just for size but to square the case mouths. Length is important for consistent crimp and release, But so is square as out of square also creates an uneven crimp around the bullet.

With most trimmers +/- .001 is obtainable fairly easily.

I have set up a trimmer to chamfer and deburr case mouths to get uniformity there also. It did cut down on unexplained fliers some. The more uniform the better but then only you can decide how far you want to go

Sounds like a Wilson Trimmer owner!

Lol!

Me too!

Three44s

[country gent]

Redding actually. and a homemade set up for the drill press.I have used the wilsons and they are good also.

[JSnover]

You'll also find the bullets measure more consistently from the base to the ogive than they do from the base to the tip of the nose.

[mdi]

While I haven't considered case trimming essential for my "accurate" rifle handloads which are not crimped, my plain old Lee case trimming system (stud, base, cutter attached to a hand drill) will consistently hold +/- .001" (and often less with a total variation of .001")...

[1hole]

There are no standards for case length variations, we each set our own limits. Chambers typically have longish "necks", often as much as 30 thou longer than "max" case length. As long as the cases are shorter than the chamber it won't matter.

Load manuals usually list SAAMI max case lengths. Then the manual makers - not SAAAMI - normally suggest a "trim-to" length 10 thou less than max because they have no reason to not think anything in that +/- 5 thou range is good enough. If you want to see if that small length variation matters for you will demand that you do a test target because we can't honestly tell you.

[mdi]

Individual cartridge case length variations is up to the reloader, but SAAMI assigns a minimum and maximum. I won't go through the task of copying and posting a pic of the SAAMI drawing for .223 Remington, so I'll just quote it; overall case length is 1.760" -.030". Meaning the SAAMI recommendation is from 1.730" - 1.760"...

[lightman]

I try for + or - .001, which I guess is a total of .002. My Lee case gauge type, my Wilson and my Giraud will easily maintain or beat this if I do my part. Like Country Gent I trim new rifle brass so that I'm starting out even and square. I also resize new brass to round off the case mouth, knowing that the die will probably not touch the shoulder.

Case trimming seems to be one of the most hated jobs in reloading. I splurged and bought a Giraud machine for the cartridges that I load in volume. It can be pretty intimidating sitting there looking at a couple of thousand 223 or 308 cases that need trimming!

[Three44s]

There are no standards for case length variations, we each set our own limits. Chambers typically have longish "necks", often as much as 30 thou longer than "max" case length. As long as the cases are shorter than the chamber it won't matter.

Load manuals usually list SAAMI max case lengths. Then the manual makers - not SAAAMI - normally suggest a "trim-to" length 10 thou less than max because they have no reason to not think anything in that +/- 5 thou range is good enough. If you want to see if that small length variation matters for you will demand that you do a test target because we can't honestly tell you.

Not always, not always!

My 788 Remington in .22-250 is an exception. Even .010” trim under chamber max was not enough.

Rifles are individuals, read the signs and play it safe!

Three44s

[ioon44]

I bought the chamber length gauges from Sinclair for each cal I load for this takes the guess work out of it.

[bedbugbilly]

This is an interesting thread. I just started loading .223 for a bolt action and have range brass as well as some new Starline. The range brass I processed and I found the case overall length all over the place. Anything 1.755 I left but was surprised on the variety of lengths I had on anything over that - of course they were "pick ups" so have no idea of X fired or in what other than I know an AR. I went with a Lee quick trim die and cutter that I used a cordless screwdriver and was careful and tried to be consistent with each trim - but I found when I checked them, the majority were 1.750 for still had some + and -. While I have reloaded other bottlenecks (30-30, 8mm, 308) I have never really had a whole lot of experience with trimming to length and was concerned on the variance I was getting on some of the 223s with th eLee trimmer. This thread has been helpful!

I'm older - pushing 70 - and this is the first rifler I have ever reloaded FMJ for - everything else cast. While I'm no sharpshooter, I put a Leopold scope on the Ruger American Ranch and am striving to keep things consistent - I am putting a very light crimp on with a Lee collet. After trimming with the Lee trimmer - I got a forming/file trimming die just to try and see if I can tighten up the tolerances on the case length. Maybe I'm too anal in my thinking on that but I'm not going to be going through a vast amount of rounds, I'm retired and have plenty of time to play with the 223 and file trimming.

Not trying to steal or waylay the thread - but could some of you perhaps cover the trimmers you use an what kind of case length tolerances you are able to keep with them?

Comfy - thanks for the post - I think a lot of us who are new to the 223 (and others) can pick up a lot from the answers of those who have worked with it for a long time. I'm old but I'm still learning! :-)

[ioon44]

I just pushed past 70, I use the L E Wilson case trimmer and it gives me +/-.000. When I use .223 range brass the case length can vary a lot, I trim to 1.760" for my AR after checking the chamber length.
Cases that are shorter load and shoot with out any problems.

[MostlyLeverGuns]

Bullet pull/uniform neck tension is probably more important than actual case length. Uniform case length contributes to uniform bullet pull. When crimping is required - tube feed lever guns, revolvers, very hard kicking rifles - uniform case length contributes to uniform crimp to uniform bullet pull. The case should be short enough to release the bullet without running into the 'end of the chamber'. I trim to the shortest case in the group or to the maximum length the chamber allows, whichever is shorter. I do like the Wilson for accuracy and adjustability. The Lee is very accurate but not as adjustable, though the newer Lee press mount may be. I prefer to trim after firing and sizing as the brass moves and length changes from both firing and sizing. I end up with plus/minus .001 or less and consider that fine.

[1hole]

Individual cartridge case length variations is up to the reloader, but SAAMI assigns a minimum and maximum. I won't go through the task of copying and posting a pic of the SAAMI drawing for .223 Remington, so I'll just quote it; overall case length is 1.760" -.030". Meaning the SAAMI recommendation is from 1.730" - 1.760"...

Not to quibble but SAAMI's max:min case length of .03" is their ammo factory case length tolerance; so far as I know, they do not specify or even suggest a trim to length for reloaders. Every load book I've ever seen sets their suggested "trim to ... " length at .01" less than SAMMI's max case length. (If they even do that, some good loading books don't even mention it.)

I won't say striving for zero variation in case length (or OAL length or weighed charges to +/- .000001 gr.) is meaningless but it hasn't made any detectable difference in my own accuracy.

It MIGHT help competitive B.R. shooters routinely getting .030" groups to reduce that average spread by a few thou but they also do a lot of other case work to get there, and they don't do it with factory barrels and hunting bullets.

[Shiloh]

I trim to 1.745. Trim It II.
If it is off, rarely more than .001 either way. If it stars to get off, I check for crud on the revolving bushing.

Shiloh