So I am getting all the information I need for this build but some things I am either having a hard time finding or I'm not sure what is correct. Has anyone heard of and used Linemount? Are they good to order from?
Big motivator to finally cram what everything that I need to get is my Phoenix Weaponry moderator clone should be getting approved any time now, submitted to the ATF Tuesday afternoon. :D Also my first "suppressor" which is exciting.

My current list is this:
For a stripped slick side upper going with this, https://www.primaryarms.com/luth-ar-a1-stripped-ar15-upper-receiver-slick-side
Rear sight kit, also Luth-AR, https://shop.brownells.com/gun-parts/rifle-parts/rifle-sights-parts/ar-15-a1-rear-sight-assembly/?sku=100024755
For a charging handle I'm not sure what version was used. On the Linemount sight they list a "601 style", https://linemount.com/product/retro-601-style-a1-triangle-charging-handle-gray/
6 hole CAR15 handguards, H&R made, https://palmettostatearmory.com/h-r-us-made-gi-quality-carbine-length-drop-in-6-hole-handguard.html
Slip ring, https://shop.brownells.com/gun-parts/rifle-parts/rifle-handguards-parts/ar-15-a1-deltaslip-ring/?sku=430106648
Currently haven't looked for a bolt yet, don't think I need to get to worried about it but I would like to be as clone correct as possible if I could
I'm not sure what to do for a dust cover. I know there were some differences in the early ones but not sure what I should get.
Tried looking a little for a front sight without the bayonet lug but haven't had any luck yet.
For the barrel, what is the actual correct length. I've seen 10", 10.3". and 10.5 all listed". And they are the pencil profiles and carbine length gas tube correct? Any recommendations for a correct one?

For the lower receiver I am correctly looking at the stripped H&R "Commando", even they I know the commando marking is actually wrong and the historical H&R never made these. Outside of getting an unmarked lower and having it engraved somewhere which I don't know where to get a more accurate lower. And when I eventually get something more correct I can still use it for something else.
2 position buffer tube, https://www.brownells.com/gun-parts/rifle-parts/rifle-stocks-parts/ar-15m16-buffer-tube-2-position-mil-spec-retro/
For the aluminum collapsible stock, from what I've read Essential Arms made a quality replica but they seem to no longer make them as they are sold out everywhere, any leads or a good alternative?
Also not sure about what to look for for a correct mag release stuff and selector switch, but I would imagine that a basic one would be good?
And I'm sure I can find some Colt bakelite grips, assuming those are actually correct?

As far as GAU-5/A details, did you check Retro Black Rifles?

That seems to answer most of the questions.

As far as Linemount, I've ordered a couple times, including with in the past few weeks and not had any issues. They seemed decen

First thing first, you said clone correct. So the upper and lower receivers need to be in grey anodizing. The upper you linked to has black ano. Only one making grey anodizing A1 upper and lower is H&R. If you get the black one, you may need to paint in grey.

Thank you, didn't catch that. And went back and checked and of course the grey is sold out.



I've used the first link as a reference for the receiver markings, but it doesn't really seem to answer some of the others questions unless I'm not looking in the right place, kinda does with some but not fully.
Nice to hear about Linemount though.

Someone sent me this link a while back.

Looks like the GAU-5/A had a 10" barrel and the GAU-5A/A had an 11.5" barrel.

GAU

That's a new link that breaks things down nicely. I've been using this one sometimes, https://www.imfdb.org/wiki/M16_rifle_series#Colt_XM177.2FCAR-15.2FCommando_Series
imfdb is one of the sources that lists it as 10", and I think that might be the actual correct length but other places sometimes list it in the other 10.3" or 10.5".

H&R upper - complete

Blem of the same Upper

Complete Lower - Commando

or use the H&R site to piece it together

Huh. I don't know how I managed to skip over the complete slickside upper. I had been doing a lot of searching there.
And this adds to the confusion, they use a 10.5" barrel. I wonder if this is the actual correct length. If you think about it, the retaining ring, handguards, and front sight block, and barrel threads are going to put a minimum length of the barrel, and anything extra will be sticking out the front. And from what I have been able to see comparing the H&R upper with a 10.5" barrel it seems like it might be correct, would be easier if there were pictures of them without the moderator on.
Oh, and you also listed a complete lower. Wow my searching was awful last night. Thank you. I feel so stupid. I had been all over PSA searching the H&R stuff and somehow never came across the complete ones, unless maybe they were originally showing as out of stock or something and are now in stock.

www.retroblackrifle.com

Click on military carbines, then GAU-5A

The GAU-5A (R630) is just an XM177E2 without the forward assist.

There's confusion because the AF retconned their XM177 (R610) guns and redesignated them as GAU-5A as well.

Sounds like you're making a 610.  10.5" barrel, 4.5" moderator, normal charging handle in gray, no forward assist upper, but the bolt carrier has the teeth.

not sure why they are called out as a 10.5" when the picture clearly shows and as i recall, Mike has said, they are 10" barrels.

You think the H&R listing is mislabeled and they are actually 10"?

from Mike on another post about the TIA uppers they make.  So yeah, its a 10" per Mike.

I think the XM177 uppers are mislabeled on the site. I'm pretty sure that the XM177 and XM177E1 uppers use the same barrel, just slick upper vs forward assist upper. I think the E1 upper originally said 10.5" also but Mike had it fixed. I put this image together using the Colt XM177E1 picture from Retro Black Rifle and the H&R XM177E1 upper from PSA's site.



I ended up pairing one of their E1 uppers with a Commando lower and a tax stamp.

I ended up ordering the complete lower and that upper. Both should arrive tomorrow hopefully. Then once it gets in I just have to wait for the SBR tax stamp to be approved. And I have been waiting for my moderator to get approved since Tuesday of last week so hopefully that happens any time now.