it might not be worth your while to chase the lands.  your HK MR556 is chambered in 5.56x45 so it already comes with a longer leade.

Yea, not trying to chase it. And there's still about 22 thousandths left on the jump. So I might experiment with more powder since there's more internal volume room left. I could always dial down on the seat too anyways with the micro seater die. I started with a longer COAL first since the ASC mags will take that without issues. I mean why not.. It's just fun experimenting. I just like finding something that works great and get a kick from it cause you've created something that works good in the end. Well, that's just me.. Like my home theater hobby habit, I can stay on the laptop with the mic position on the MLP all day running test tones until I can get a flat line down to 5hz @ 100 db .. lol.. and that's a different part of hobbies I'm so tidious on.. But in the end, sounds friggin 10x better then the newest local theater.l. Lol..

Nice! On what length barrel and COAL? I'm just playing it safe right now. Staying ..3-.4 below recorded max data. I'll work up slowly for  now, I'm just trying to see what powder shoots accurately and consistently first. Then I'll take it from there. My COAL is around 2.308-2.309. With jus the right amount to be feed through the mag and get the ogive closer to the lands. Though, still get atleast a .225 bullet jump left even when I'm at 2.309. Cartridge base or brass I'm using to ogive or lands  is 2.089. Sierra TMK bullet ogive to top of bullet I came out with 0,445. + the 2.089 come out 2.534. So even if I made the COAL to 2.31, still get plenty more jump.. lol. But atleast I got the bullet more close. Being that said, I can probably pack more powder later but watching out for pressure signs. Hmm, I might experiment with with 80's single, hand fed though.. later maybe..

20" barrel 1x7 twist My load is LC cases, Rem 7.5 primers, 24.1 RL15 topped with a Nosler 77 at mag length. With 80s I load with 24.3 RL 15 seated out for .005" - .015" jump.
More info here: http://precision.whiteoakarmament.com/info-reloading.html
some may disagree but load dev has been done extensively with .223 already. There are proven loads and more often it is the gun or the shooter. By the time you find that one load, you may already have burned through some barrel life.

Agree. That's another reason why I don't bother with OCW as much. I do it more to see which powder load gives me the tightest group for the fun of it. I've been working with RL15 and Nosler 77 for the past two months and really liking it. The only problem is that RL15 doesn't meter well so a lot of hand measuring is involved. I'll probably start working with TAC more in the near future. It worked pretty well with the Nosler 62 I got. I have a 24" 1x8. I haven't played much with the COL yet and just seat to what's listed in the books. Something else to play with later.

Would you say the Lee Measurer is more accurate than the RCBS Measurer with the extruded powders? I could drop Win296 all day long at 0.1 gn accuracy but the RL15 varies about +/- 0.3 gn.

I had the RCBS and had it on my Dillon. I didn't do a sample of drops. I did notice that the RCBS cut extruded powders more than the Lee PPM.  The RCBS was great with ball powders. The Lee PPM was accurate but tended to leak with ball powders - so I stuck with extruded on the Lee.

20" barrel 1x7 twist My load is LC cases, Rem 7.5 primers, 24.1 RL15 topped with a Nosler 77 at mag length. With 80s I load with 24.3 RL 15 seated out for .005" - .015" jump.
More info here: http://precision.whiteoakarmament.com/info-reloading.html

some may disagree but load dev has been done extensively with .223 already. There are proven loads and more often it is the gun or the shooter. By the time you find that one load, you may already have burned through some barrel life.

I can relate to your hobby in home audio as I was a car audio fiend a long time ago. Spent a lot of money and time with horn loaded compression drivers in the car and trying to find that flat response curve along with good staging.
The Holy Grail was this Grand National
http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/192169-what-ever-happened-richard-clark.html
In the end, I spent more time tweaking than enjoying. Was it worth it? Nope. In the grand, galaxy of things it didn't fit (car audio) in my renewed perspective of life. Anyways, live long and prosper.

for extruded powders like RL15 I use this


for about $20 and its pretty much spot on - Most times I just dump straight into the case

I also progressively load on my Dillon 550 with RL15. I polished the Dillon measure