I'm not the original poster, but I'll give it a go - do they sell an extended box for the .223 length, and if so, what is the max COAL? Everything that I saw looked to be for the .308 length.
What model are you looking at? Ease or complexity of installation is dependent on the model. Some require the action be milled, bolt stop modified, and ejection port opened up. Some don't require any of these.
Some are plug and play, some require tweaking to get the cartridge at the right height for the bolt to strip it from the box.
OAL is determined by the model.
Go to Wyatt's site (HERE) to see the variations in models.
Wyatt's isn't a detachable mag though right? I talked to Stiller about putting together a long .300wm (3.615") and they said i needed a Wyatt's box but I neglected to mention I want detachable mags..I figured I needed a .338LM action to make this happen, they said I could use the regular LA predator but needed the Wyatt's box...
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Powder Burns</div><div class="ubbcode-body">Would that RUM/Lapua DBM work with a .300wm or do I keep looking? </div></div>
You'd have to call Wyatt's to get the straight dope on that. I don't have any experience with their detachable system and would hate to advise incorrectly.
I put one on my LTR in .308. I love it. No problem reaching the lands from the box now and my rifle shoots basically benchrest accuracy loaded that way. You do have to mill the bottom of the receiver and shorten the boltstop. Also use the flat follower that comes with it and bend the feed lips from the BOTTOM and polish the top edges. You do lose one round capacity, but your new extended rounds hold around 3 more grains of powder.