I am getting ready to order my upper .458 SOCOM from Tony @ Tromix, who has been very helpful in answering my many questions.  I lean towards the standard A3 upper with forward assist and ejection port cover.  Tony mentioned that with the A3 and functional port cover, the brass skims the top of the port, and for better ejection performance, he favors the DPMS slab-sided Lo/Hi Pro.  Tony seems to be a perfectionist and since he wants to produce the most reliable upper he can, he of course favors the lo/Hi Pro, but I would appreciate input regarding uppers from you that have them.  Now the question.  Have others with the A3 upper with port cover found the brass skimming the top of the port to be a problem pertaining to ejection reliability and damage to the brass?  Is forward assist beneficial at all (this rifle will not see any combat or tactical use, hunting and BS will be all the action it will see)?
 My instincts tell me to go with what Tony recommends, but for reasons I cannot express I really like the ejection port cover feature and forward assist (even though I have never used it on either of my other ARs), but not at the expense of reliability.

Thanks in advance.

I've got a 458 A2 "dissipator" style-upper, and have had zero problems with the ejection port.  Fact is, the ejected cases are shooting out almost directly to the right...not even a ding on my case deflector after over 200 rounds.
Sluggo

Anyone else?  Opinions on which is the better liked upper: A3 or Lo/Hi Pro?  I need to order soon and would appreciate your opinions.

I have the lo/hi pro upper from Tony in .50AE. [b]When Tony talks, I listen.[/b] He is indeed a perfectionist.

Bob

I have the Lo Pro upper, my buddy has a flat top with a dust cover. On his, they removed metal to make the ejection port larger, now the dust cover doesn't stay closed. I personally like the look of mine. I wish I didn't buy it, but it is nice now that I have it.

2 buddies have the 458 w/ dust cover. Zero problems and the dust covers are functional. I like the std sights over the flattops - batteries never go dead.

The problem stems from all the receivers/port covers are not identical.  Even tiny variations in the amount of travel in the door cover detent can limit the amount of material I can remove from the top of the port.  I have to machine the port opening with the door cover installed and continually check the latch engagement as I shave off a few thousandths at a time.  If the door cover detent happens to have an extra .010" travel, then I can raise the port a bit more, and so on.  So, yes, it works, but you're always on a C hair getting it to work with a functional door cover.

Tony Rumore
Tromix Corp