I'm not sure if I fallowed along correctly but:

If the bulk of your brass was from new FC .223 ammo that is why they are short.

FC brass is NOTORIOUS for being short. Some guys like it because it means it won't need trimmed until after a couple or more sizings.

While many others (who are very picky about "their brass") won't even use it.

The SAMMI spec is 1.730" to 1.760"

If it's within the standards of the governed body that sets those standards it's good enough for me.

Motor

I didn't trim it because it needed it, I just always trim brass as part of my normal case prep.  It only takes a few seconds to set up the drill press to do it and then the outside deburring step makes a weird sound if the mouth has a crack or a big ding in it.  Since my brass almost always has at least a few range pick ups in it, it's easier just to trim it all and not worry about it.

So when I said it was trimming most of the FC cases with the Imperial instead of STP, it might have only been trimming a .001 or 2.  I did not mean to imply it was over 1.760".  I've never measured it out of the rifle.  The difference this time was 95% of the brass didn't even touch the trimmer.

The length of fired brass means nothing. Brass typically gets shorter when fired because it expands basically drawing in it's length.

What I was trying to tell you is Federal brass is normally short and typically won't reach normal trim length until it has been re-sized a few times.

Brass grows when full length sized for the same (opposite) reason it gets shorter when fired.

ETA: One more thing. The amount a case grows when full length sized depends on how much the sizing changed it's shape, mostly it's outside dimensions.

So if your rifle has a "tight" chamber (meaning made to the small end of the tolerance in diameter as well as length) your brass will be worked less and grow less when sized.

Motor

I think the initial conclusion is that sizing with Imperial or other lubes caused cases to lengthen, while sizing with STP apparently did not cause the same amount of lengthening.

My thoughts are along these lines: we typically think of firing as the cause of brass "flowing forward" and lengthening cases, but there's plenty of reason to believe that instead a good bit of the lengthening is related to the sizing operation.  The mechanism would be that the die reduces the case diameter and pushes the shoulder back, thus pushing material forward.  Now here's the rub: why is it different with a much slicker lubricant?  The cases appear to have a more consistent headspace dimension, and I'd imagine that their diameters are also consistent, so why does a case sized with Imperial wax get longer when a similar case sized with STP not get longer?

The way to figure this out is simply to do a LOT more observations.  Maybe the rifle in question had some sort of "perfect" chamber and all FC cases will remain short out of that chamber.  Maybe it was an exceptionally short batch of brass to begin with.  Looking into this would require before and after measurements of length (and maybe headspace dimension) to compare individual cases and how they react.

This is a fascinating subject.  But it's certainly not a simple one!

BRAVO!  Sticking to your gunz and not overreacting to the naysayers, to the point of never trying anything new, gave you something many others will never have....first hand knowledge of one of the best case lubes ever, STP.

I especially love your original application method.....that even Dryflash3 might like.  Okay, to be honest the lanolin users started it.....Dryflash's version is spraying lanolin in a cardboard box, which is why he asked you if the lube was thin enough for his spray bottles.  STP has to be dabbed and kneaded in a plastic bag, which works on the same principal, and even a bit less messy.  Thankyou for that!

That link to the STP 60:40 you guys found was in my Firing Line thread, so I know a little bit about it.  Bart B., who is one of the most knowlegeable people who reloadz for competition was the author of post 10 where he shared it.  I commented in post 11 that I'd have to lose the Hoppes as my wife hates the smell.......

Uncle Nick, moderator there, who also took interest in that thread, said, "I've never tried mixing STP with Hoppe's, but I have mixed it with odorless mineral spirits and Kroil. Either thins it. They may trouble your spouse's olfactory senses less than #9, though they won't clean powder residue off as well. The mineral spirits are particularly slow to affect powder carbon and graphite."  For my limited testing, I did as you did and used STP straight, along with the newish RCBS water-based lube pad lube.  STP by itself is about the slickest stuff there is.  I've even heard rumor that the old original RCBS lube pad lube was STP.....but couldn't verify that.

My thread was originally on testing the then new RCBS Summit press against a Rock Chucker II......using horror of horrors, the same made in hell LC machine-gunned brass you found, worse, it was wet-blinged first in a Thumler's....who woulda thought that would add to the friction?  My thread intent was different from yours, but the total failure of Imperial Wax on that brass was exactly the same!  In my tests the I could not have found a harder test for a press, and using Imperial it almost was a non-start-disaster.  I don't use the wax anymore.....works fine for a lot of people, but it ain't the best.  

So after my experience with lubes in my project,  STP was best and the RCBS lube pad lube was real close, lanolin was just okay. (Within the window of time between alcohol-dry and lanolin-dry). Lanolin dried and lube attempted a day later was a disappointment. This was Dillon's product not the homemade formula, but I think they are nearly the same.  Keep in mind this test was the worst test....most lubes work for lesser tests, especially pistol, yet if you think the wax is great on pistol....don't try STP/RCBS water-based....you may hurt yourself.

Uncle Nick suggested the vegetable based lithium grease.....sposed to be the cat's meow in automotive on the slick scale.....he didn't try that and neither did I.

The after-mess or what about cleaning?  I've never met a lube you shouldn't wipe off.....or tumble off if you're a believer that it's safe.  Did I say I really like TripletDad's idea of using the lube dab and bag!.....that makes the mess controllable.

PS.  Bart B. and UncleNick turned my thread into a really informative treatise on Case Uniformity, honing a regular sizer dies for that, for those interested in more education.  I was reviewing the RCBS Summit Press, and learned a great deal in the process.  They have a lot of credentials between them.    

Sorry pictures in my "FiringLine" thread was highjacked and destroyed by Photobucket as they have also done to millions of photos all over the net.  Many of Dryflash3's included.  If anyone has a desire to copy that firingline thread for the information, I will send them the pictures that go with it.  Firingline at this time are not allowing people to go back and edit damaged threads.  AR15.com has no such limitations. (I found Postimg.com who "encourages" my 3rd Party embedding.)

GWhis got me thinking and as it happened today, my eldest (by 45 seconds) and I went to the range.  We were shooting some of the once fired brass mil brass that I processed early last month.

Conclusion
STP is 30% better at minimizing case growth variation during sizing than Imperial.

Procedure
I took the 40 first time reloaded cases (WCC-10 NATO +, not annealed after the original resizing, weights 177.x grains after processing) that we fired today and

Annealed
Tumbled in walnut for 15 minutes
De-capped with a Lee universal de-capper so primer issues would not effect case measurement.  There were no pressure abused cases, I just thought it would make measuring more consistent.
Numbered and measured* each case.  Only the 1000ths over 2" was recorded.  For example on the first case, it measured 2.006" before sizing, 2.013" after sizing for a growth of .007".  The case number and measurement was written in sharpie on the case.
Sized cases 1-20 using STP.  The die was not cleaned beforehand because I'd being using STP.
Decapping/Expanding stem removed from the die and the inside of the die was cleaned in place on the press with a paper towel.  Stem replaced.
Sized cases 21-40 using Imperial sizing wax
All cases were tossed in a box after sizing.
After sizing, the box was shaken and I measured* each case without looking at the case number.  The measurement was recorded.
Entered into excel

* each case was measured 3 times with a 45 degree or so rotation between each measurement.  The recorded value was the average by eyeball of the readings on a per case basis.  The tops of the case mouths were not always square so there could have been a .001 to .002 difference when rotating.


Results



Summary
STP had around 30% less case variation in standard deviation and extreme spread than the Imperial although both showed very close to the same amount of growth.




Other notes
Both lubes did not take much effort to resize cases fired in my rifle.  MUCH easier than when they were fired in a MG.  However, the STP required a little less effort than Imperial.

The cases resized about a month ago in 60:40 and 100% STP do not have any visible discolorations.  Everything still looks fine to me.

Oops, forgot to add.  I just full length resized by screwing in the die to my mark and going from there.  I know I'm over sizing, but I want these rounds to work in any .308, so I'm not just pushing the shoulder back a few .001ths.

TripletDad, have you tried motor oil?

I have two containers of ANY case lube.

One is new.

The other is open.

When the open one runs out order a replacement and open the new one.

It is not all that hard to plan this stuff.

I remember when wet tumbling was rejected as a waste of time and effort.

I also remember when tumbling loaded cases was deemed harmful to the powder and primer...

I guess some of use don't want to see the value in OP research and effort. I do...

Its not only about having a cheap alternate case lube. Its more about discovering a more consistent resizing method via the case lube.

For me, if I can get a better result using a cheaper product, I want to explore it. So thanks Tripletdad for your time and effort...

No, I've not tried it.  I've watched the link that Twoboxer posted on the first page, however I'm somewhat neatness challenged.  Even with a pool of oil only 1/8" deep, I'd figure out a way to spill it.  STP stays stuck on the inside of the baggie and is not going anywhere.

I don't think oil would be any worse to clean off than STP is, but if you're going to wet tumble with pins, I'd think that would take it back off without a problem.  Dawn is good stuff.

If you do try it, I wouldn't consider it a hijack to post your results in this thread.  I'd like to know.

Why?

Are you thinking about a process known as "season cracking"?

"Season cracking" is a term applied to damage to brass cartridge casings caused from exposure to high amounts of ammonia resulting from the ammunition having been stored in a stable for several months (hence the term "season" cracking).  It was a particular problem for the British Army in India during the late 19th and early 20th Centuries.  The ammonia formed an intermediate compound with the copper portion of the brass alloy known cuprammonium along the stress cracks that remained in the cold-formed brass cases.  

The problem was solved by removing the residual stress cracking by annealing the brass.  So, it is not clear whether modern cartridges - which are annealed at least once during the manufacturing process - are even susceptible to season cracking.  But it is clear that a few hour or few days exposure to solvents with low concentrations of ammonia are simply not concentrated enough nor is the exposure long enough to cause season cracking even if the brass is susceptible.

Just about anything that can form a thin film; be it lanolin, glycerine, lard, tallow, chicken fat, vegetable oil, motor oil, oil additives, and the like, can be effectively used as a case lubricant.

I tried a number of case lubricants over the years and eventually settled on Hornady Unique.  A small tub cost $3.99.  I have lubricated over two thousand cases - the vast majority of which came out of semi-automatic rifles and several hundred fired from a San Cristobal submachinegun - with it since I bought it and I can hardly tell any has been used.  The Unique tumbles off in corn or walnut media in a couple of hours.  I expect to realize somewhere between 12,000 and 15,000 cases out of the one tub before it is used up, so the cost savings of using bulk lanolin, a can of STP or a bottle of canola oil are barely enough to justify the additional trip to a second store.  I did buy a second tub of Unique on the off chance I shoot more than 15,000 rounds throughout the rest of my life.  $7.98 plus tax for a lifetime supply of case lube seemed a reasonable price to pay.

I just did another test today of STP vs lanolin and ISO.  STP is still the winner.

I made my cheap bastard lube with 1:11 mixture by volume of Home Health liquid lanolin and red Heet isopropyl alcohol.  Whoever was worried about the smell of STP earlier hasn't dealt with Heet, this stuff made my eyes water.  STP has less odor.

I had 75 .308 cases that had been fired for the first time in my Savage.  All the cases were WCC-10 with the NATO cross and were sized the first time at the very beginning when I started looking for a better lube.  37 were sized with the cheap bastard lube, 38 were sized using STP.

The first thing the cheap bastard lube did was erase all my sharpie markings on the cases.  So I do not have case by case measurements for the lanolin like I do using the STP.  So I'll only report the averages and standard deviations for each method.  This also killed my experiment to attempt to measure case growth during resizing.  I could measure the STP cases, but I wouldn't have the lanolin comparison, so why go through that major PITA?

The 37 cases sized with lanolin
Start: Head space 24-33 cases 25-4 cases, average 24.11, stdev .3148
After: Head space 20-1 case, 21-20 cases, 22-16 cases, average 21.41, stdev .5507

The 38 cases sized with STP
Start: Head space 24-30 cases, 25-8 cases, average 24.21 stdev .4132
After: Head space 20-1 case, 21-37 cases, average 20.97, stdev .1622

"Head space" was measured with a Hornady head space comparitor.  The way I'm reading the standard deviations, the STP took a worse sample of brass and turned it into a better sample of brass.  STP is a superior lube in regards to head space consistency after sizing.




The difference in sizing effort between lanolin and STP was insignificant.  If you twisted my arm and made me pick, I'd go with the STP having less effort.  But in a blind test, I don't know if I could pick it out or not.

The lanolin cases were more pleasant to handle after sizing during measuring.  The were kinda sticky and didn't get on your fingers nearly as much as the STP.  I still think you'd have to clean both before further case prep steps anyway, so IMO, this is a wash.



There is still no observable appearance change in the cases sized in STP and 60/40 STP & Hoppes back during the first week in July.

I just found your topic today.  About 25 years ago when I started reloading my mentor used nothing but commercial Breakfree for a sizing lube.  We would just apply it to an RCBS lube pad and nothing else.  I wasn't particularly concerned about cleaning off the lube, that is, I didn't go through any extraordinary measures to remove it.  I would simply wipe it off with whatever was handy, a paper towel or cloth rag.

I'm simply going off memory but I know that I sized once fired LC .308 cases back then that weren't LR so MG use was probable.  I would generally run them all through a small base die the 1st time and standard RCBS FL die after that.  I was also reloading .25/06 at the time starting with new Winchester brass.  I know I did some .223 as well but it was for a bolt rifle.

I didn't document anything specific back then but my memory seems to support what you're finding.  I don't think I was trimming as much then. I may be trimming more now as I do use Imperial.  

The only thing I can add is that if you're going to try something like an oil for sizing, keep it only on the body of the case just as you would with sizing wax.

I never had any kind of contamination issue with primers or powder.  I never used oil to lube the inside of the case neck.  This was all loaded single stage though.  If I was to try using this with a progressive press I'd still prep my brass in stages so it wouldn't matter.  I would have everything sized and cleaned already so that when I put brass into station 1 on my Dillon 550 all I am doing is seating a primer.

Virtually any liquid that will stay in place on the case and not break down or gum up under the pressure of resizing will work as a lubricant.

The considerations that would go into a decision about which to use would be cost, convenience, ease of application, ease of removal, effectiveness, toxicity and cleanup of hands and equipment.

After 40 years of trying everything from glycerine to motor oil, to RCBS sticky tube lube, Lee's toothpaste tube lube, various lanolin preparations and so on, I settled on Hornady Unique. A tub costs $4, it is applied with the fingers, tumbles off easily, doesn't break down when forming cases, can be wiped off with a paper towel or rag and since its principal ingredient is tallow, it's practically edible.  And after 6,000 cases, I can hardly tell I've used any at all.  That combination of factors works well for me.