I'm looking into what upper to use for a lr308 build and am wondering if the M5E1 upper needs squaring? Was going to use the PSA pa10 upper and lower but that seems like a hassle and might just use the regular m5 upper lower combo and square it on a lathe. Any input on these uppers would also be appreciated.
Really no way for us to tell. Aero is good stuff but nothing is 100%. Many many builds with all kinds of lowers that were not squared and unless off by a lot, probably give satisfactory results for what many of the builds are used for.
My first 3 builds were not squared but did do the last one (Aero, not a M5) just to be safe. Cannot tell if enough differences to say it was the squaring are the last two were ARP barrels.
I just lapped an Aero M5 upper last night. I was having to dial in considerable elevation when I transferred a scope from another rifle (Bobro QD mounts) prior to lapping. When I took the newly trued upper to the range tonight and borrowed a scope from a different rifle (again, in a Bobro QD mount), I hardly had to touch the elevation (and only had to add about 5" of windage at 100 yards). So, IMO, yes, the Aero receivers can benefit from lapping. This is one reason I stuck with the M5 over the M5E1 since this is a precision build.
Edit: for those that didn't catch on, there is no lapping tool available for the M5E1 as the standard PTG AR308 lapping tool won't work.
I think just general concerns of compatibility with aftermarket parts for the platform. If you stick with PA parts you should be good to go and be able to build a very fine rifle, but careful research is suggested if you want to go too far off the PA reservation.
On the other hand, the Aero M5 pretty well conforms to the DPMS "high" spec, although use of their elongated take-down pins is recommended.
Just don't want to be stuck having to use PSA parts since they are not always in stock. Boiler up was right about compatability and going off the reservation as well. Large frame Ar's sure are a pita compared to ar 15. Might still try using PSA since the price is always good but I would like to pick a platform and stick with it for this build and future builds. Dpms LR308 seems to be the most common. Did the next gen uppers fit the PSA lowers?
Can the M5E1 be squared on a lathe? Just want to make sure everything is true with whatever platform I go with. I know mega doesn't need it but they are out of my price range.
The trick is the face you need to make square is, basically, recessed within a tube. So, your cutting surface will have to be big enough to hit the face, but small enough to fit in the recess. I'm sure a fixture or even traditional lapping tool could be produced, but I suspect you are on your own to figure it out.
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