80% 308 build

[willbird]

18 hours ago, Albroswift said:

Three 80% millings done so far, a "Cheapest on the internet" AR15 Anodized Forged 7075 for practice, a 9MM Anodized Billet 6061-T6  from 5D, and a 308AR Anodized Billet 7075 T6 from American Made Tactical. They all milled cleanly, but the AMT 308 slightly cratered the 3 drilled holes (Safety and FCG) . Like a little ridge  around the hole. Not sure if it was the 7075 aluminum, anodizing, or ? but pretty sure  the drill bits are not to blame, like new. Also had a heck of a time punching the holes through, bits grabbing like nobody's business. Didn't have that problem on the other 2. Using an aluminum cutting fluid, maybe go back to WD 40 for drilling. 

Correct anodizing the surface is actually as hard as sapphire. 70 Rockwell is the aprox hardness but you cannot use the rockwell test process. A HSS drill bit is about 60 Rockwell C.  So proper anodizing is harder than an HSS drill bit and will ruin their cutting point. Spotting with a 120 degree carbide spotting drill will get through the anodizing, probably most jigs do not provide bushings to do that from each side ??

[willbird]

Honestly if you buy a bear creek barrel building an upper might be cheaper than  PSA uppers perhaps. Then you can use whatever upper the 80% mfg says works best. You just need a barrel wrench and a reaction rod.

[Nate40]

On 6/17/2019 at 4:51 AM, thequintessentialman said:

98Z58

Nothing is set in stone here, I simply mentioned the PSA as a starting point.  I'm open to suggestions.  Most of the stuff I'm running across on the web, is a bit dated hence the reason for asking.  I did send an email to Hell Fire to see what they had to say. 🙂

Thanks

Every one I built of psa ar10 on a 80% dpms lower were poop no fitting without drilling and grinding buy another ar10 upper never again for me

[shooterrex]

Yep Palmettos stuff only fits Palmettos stuff without a LOT of work.

[Mason88]

So, to answer the ongoing question. I put a PSA, P10 upper on this lower. It fits, kinda. There is a slight gap at the top of the lower, and the charging handle prevents the rear takedown pin from fitting. The solution is easy, use the speed bore to remove 1/8" off the top of the lower, where the buffer tube threads in. Lastly the takedown pins included with the PSA build kit are long enough to function, but are about 3/16" short of being flush. All said and done, it's a solid rifle, and perfectly functional.

[jtallen83]

35 minutes ago, Mason88 said:

It fits, kinda.

 

35 minutes ago, Mason88 said:

The solution is easy, use the speed bore to remove 1/8" off the top of the lower, where the buffer tube threads in.

So the PSA upper does not fit without modifying the receiver then, more simply, it doesn't fit.

[DNP]

2 hours ago, Mason88 said:

So, to answer the ongoing question. I put a PSA, P10 upper on this lower. It fits, kinda. There is a slight gap at the top of the lower, and the charging handle prevents the rear takedown pin from fitting. The solution is easy, use the speed bore to remove 1/8" off the top of the lower, where the buffer tube threads in. Lastly the takedown pins included with the PSA build kit are long enough to function, but are about 3/16" short of being flush. All said and done, it's a solid rifle, and perfectly functional.

Got any pics of the mods?  Could be useful for someone trying to do the same at some point.