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Does Aero M5E1 upper need squaring

9K views 14 replies 7 participants last post by  BoilerUp 
#1 · (Edited by Moderator)
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.
 
#4 · (Edited)
Not if they are square.

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.
 
#6 ·
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.

 
#8 ·
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.
 
#10 · (Edited)
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?
 
#13 ·
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.
 
#14 ·
Thanks that was the info needed. Didn't know how the M5E1 worked or if it was already square. Looks like the regular m5 will be in my future . What are the advantages and disadvantages of dpms high or low? I believe aero and mega both do the high but low seems to be better for getting a good cheek weld on regular stocks with out risers. Idk really, just guessing about that though. Handguard availability seems to be not a problem for either one.
 
#15 ·
Thanks that was the info needed. Didn't know how the M5E1 worked or if it was already square. Looks like the regular m5 will be in my future . What are the advantages and disadvantages of dpms high or low? I believe aero and mega both do the high but low seems to be better for getting a good cheek weld on regular stocks with out risers. Idk really, just guessing about that though. Handguard availability seems to be not a problem for either one.
Generally speaking, the Enhanced uppers are square, but like most things in life can benefit from a little extra attention. I suspect the anodizing process creates more opportunity to benefit from lapping than the machining of the upper itself. My 16" ARP 6.8 SCOUT started off in an M4E1 upper and accuracy was superb. I moved it to a lapped standard upper and accuracy was unchanged (as one should expect) but my optics took a little less adjustment from center to zero. For most builds, I wouldn't worry too much about it. My M5 is a precision build based on a relatively expensive barrel so I wanted the option to lap the receiver if I deemed it necessary. Ultimately, I did just that, as mentioned above. The other disadvantage to the Enhanced uppers is you limit your selection of handguards. Granted, the AP M5 handguards are very nice, but if later you decided you prefer skinny handguards you are SOL. The main advantage to the enhanced uppers is they are stupid simple to put together - fantastic for beginners.

The difference between DPMS High and Low is only 1/16th of an inch so you won't notice it in you cheek weld. DPMS high seems to be most common, but there are good handguards available for either.
 
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