Need confirmation before I start .308 80% build.

[andrewj]

I finished a few .223 lowers a few weeks back and now I'm ready for a few .308's. Is the process of milling a DPMS pattern .308 lower the same as an AR15? With reference to the rear takedown pin, are the cuts in the .223 and .308's identical? Or do any pocket depths change on the .308 lower?

[yari]

Its the same.

[dchang0]

You don't reference off of the rear takedown pin; it's the front takedown pin if following the blueprints.

Otherwise, yes, the pocket is basically the same as for a .223 lower.

kcstott has provided the first freely-available LR-308 blueprint (previous ones cost $$) on his website--check the sticky at the top of this forum.

If you are building a Quentin Defense LR-308 80%, there are a few threads here describing out-of-spec issues that you'll have to address. In my case, the selector detent pin hole was too far forward--I had to "split the difference" between the actual location and the blueprint-specified location, and the bolt catch plunger hole was too shallow. Given this problem, if I had referenced off the rear takedown pin hole, I'd have really botched the lower, because what me and a couple of others discovered was that the entire grip tang was basically too far forward from the rear.

[kcstott]

Out of the three or four prints I have the largest difference is between a AR10 and a LR308the dimensions from the front take down pin to the hammer pin is different by .058" to .059" between the two AR308 prints I have is only .002"

From that point the dimensions are exactly the same. The position between the hammer and trigger pins the depth from the top surface and the position of the selector are all identical to the AR15 it is just how far back from the front pin does the pattern starts.

do not get the AR10 print confused with the AR308/LR308/SR25

And the SR25 is the odd ball. it's a close duplicate to the AR10 but it uses LR308 mags