Ok, so per my lee data book.  minimum COAL should be 2.250. Ok got that... However, I just measured a few Hornady factory rounds and they measured on avg 2.237 COAL. They are the steel match. is this why the COAL is less than the minimum stated in my book? Curious to know.

2.25 is max COAL for AR15 magazine use. If an accuracy node is found at a shorter COAL then no harm in loading to shorter lengths (within reason).

I load mine @ 2.230 because that's the longest length that runs well in all my mags.

OAL is measuring case bottom to the tip of the bullet.  For this reason, and the cheap(er) 55gr FMJBT they use in the steel "match", you may be measuring inconsistent OAL.  Measuring from the bullet ogive is a much better depiction of where the bullet will be positioned.

As mentioned above, OAL is important for magazine length, but not necessarily important for accuracy.

2.26 will run in most mags, but you have to take into account variances in bullets and cases for commercial ammo.  You can measure each round.  They cant so they set up with room to spare so they are always in under max.  I set up for 2.25" but measure some up to 2.255".  As long as none exceed the 2.255" I leave my seating die alone.

Good stuff! I set my seating die a few moments ago. I am getting between 2.2495 to 2.251. this was will 5 consecutive rounds. I imagine the variance is due to the bullet variances due to manufacturing.

I'm a newbie, so I just want to be certain. This is my first time loading anything other than 55 gr fmj

I am also new and have set my seating die to avg right at 2.250" with SS109 bullets. So far the 200 rounds of my reloads I have shot have run with no issues in Pmags and Gi mags. I have some 77gr match kings I am going to try next chance I get to sit down and load some up.

 Forget what Lee says about OAL it means absolutely nothing to the handloader.

Things you need to know about OAL.

In an AR-15 Max mag length is 2.260.  You can load longer than 2.260 if you wish, but you will be loading single-shot and you will increase pressure.

Seating shorter than 2.260 is perfectly acceptable within reason (don't seat past the Ogive).

Seating deeper decreases pressure, seating longer increases pressure.  

Seat the bullet deep enough for adequate neck tension.  An often used "rule-of-thumb" is seat at least one bullet diameter into the case.  In a 223 that would mean .224 inches of bullet is seated into the case neck.  Not written in stone, just a rule-of-thumb.

Some manuals don't even list the OAL tested it is that un-important.


OH, and one more thing.  What Hornady 75gr bullet do you plan to load?  If it is the A-Max, it cannot be loaded to mag length (2.260) and must be loaded single-shot.

SS109s have a TOTALLY different Ogive than other bullets.  Your setting on your seating die is only good for that bullet.  It will need to be backed out for SMKs.

Which Hornady 75's?  They make two the BTHP and the A-Max.  Hornady states that the A-Max should be loaded much longer than Mag length and should be loaded single-shot if used in an AR.

I already figured that out. Just putting the bullets side by side on the bench and the diff is very plain to see.