Case max length - really max length

[Near miss]

Hello,

I just started reloading and every once in a while come across some matters that arise questions.
One of these is case length. When checking case lengths of my Sako range pickups after resizing, I got few that were over 1,765". Couple were over 1,768".
I tought that once resizing increases length by 0,02mm / 0,0078", they had to be oversized to begin with.

I put one of the longest cases in my chamber and checked with the bore scope. It seems there are long ways to go until I run out of space??
I have understood that case length is one of those things that you do NOT go over.. But is it, really?

In the picture is HK MR223 barrel with two different cases. The shorter case is PMC. The longer case is blackish because it was painted with a marker as earlier I tried to see if it would get marks on it from chambering but I could not see any.

Now, I do not know would I change the max case length for me based on this alone, but this longer case length compability would give me some leeway.

 

[Steel head]

They make tools to measure actual neck length
I make my own on the lathe.
Or through a Hornandy modified case and then compare to a fired case to get actual length.

 

[Molon]

Get a chamber "case length" gauge. The max case length for 5.56mm/223 Remington is 1.760" but most of the Colt AR-15 chambers that I've gauged have a "case length" of 1.780".

....

 

[Near miss]

Thanks! So clearly there is some extra to play with, good to know. I read some takes on other forums via googling of some barrels having that extra .02 but I of course took those with a dose of salt. I might make one of those by fitting 22LR brass inside the 223 case mouth.
Do you trim cases longer than 1,76" by the result of that measurement?

 

[Molon]

Thanks! So clearly there is some extra to play with, good to know.

Keep in mind, that has to be determined for each individual barrel.

Do you trim cases longer than 1,76" by the result of that measurement?

No. At any point in time I could be loading for 10 different AR-15 barrels. I don't want to risk accidentally using a longer case in a shorter chamber.