I had built an Aero M5 lower that sat here in my office for some years waiting for me to get more interested in it. I'm not wild about these things, don't know that much about them but its good to have one in case someone tells me I can't have one. It was fun to build it but I didn't want to build an upper. I got an email last week indicating a sale on a complete upper that I couldn't pass up. It arrived today, I put a scope on the thing and its time to feed it some.

What should I feed this thing? 308? 7.62x51?

I'd just try a couple of flavors or three of whatever ammo you think will serve your purposes. I don't believe there's any appreciable difference between .308 and 7.62 NATO, at least as far as pressures are concerned.

It's cut for a 308 chamber sounds like, so nominally whatever you want. However, my personal opinion is maybe stay away from the spiciest of loads as a precaution, as the complete uppers tend to be overgassed

If you can find Hornady American Gunner 155 grain BTHPs, those shoot accurately from my AR as well as bolt guns. Velocity is on the slow side, but they shoot great.

I picked up some 155 grain BTHPs with cannelure and loaded with a mid range load of IMR-4895 these are about 100 fps faster and just as accurate.

What are you going to use it for?

Hunting? Targets?

Thanks everyone this is helpful.

I'm not going to use it for much, certainly not hunting. More likely I'll sight it in and punch some paper now and then with it.

If I have a rifle that is primarily going to be used for paper with some chance of being employed for game or home defense, I also tend to look at Hornady's budget hollowpoint loads. Like many, I've killed game with them and also shot decent groups with them.

You don't handload? That is what I feed mine. Other than that, just use 308 winchester. That's not saying you can't use 7.62 ammo in your rifle. I have a buddy that is running an M5E1 with 18" barrel and he uses old Australian F4 ball in his. I believe his is a BA barrel, and quite accurate. He says he's sitting on 20,000 rounds of that ammo, so he "has to shoot it in something".. The best thing to do is try different ammo. Get ammo that will suit your needs and shoots accurately in your rifle. I wouldn't be going out and buying match grade ammo for it, that is where handloading comes into play..

I am using RL15 and 155 TMK's in my 308 AR. They shoot real well and seemed to fly pretty well at distance.

I'm sure they do. 168's always worked very well in mine. It's a 308w though, that should just about say it all.

Oh I do handload for sure. And I might well do that for this rifle, we'll see how much fun it is or not. It sure is a heavy bugger. Oooofff.

I built an entire AR-15 several years ago and then built this lower during boring conference calls and it just sat here in the corner of my office. I got an email flyer for a very advantageous price on an Aero complete upper, 18" chrome moly bbl chambered in 308. So when it arrived I put a scope on it which I had at hand also, and will go from there.

I appreciate all the advice and guidance, all this makes sense to me. Glad to have your experiences to give guidance.

Cool man. Then the sky is really the limit. An AR10 308 is pretty simple to load for. You will be limited to mag box length, but just find the best shooting load at that length and you'll be fine. I've ran 150gr FMJ's in mine for just plinking around and up to 180gr Nosler partitions, incase I ever wanted to take it elk hunting. Like you though, I found mine just too heavy when loaded up and scoped to enjoy out in the hunting fields. YMMV on that one though. They are fun at the range for ringing steel and punching paper though.

Thanks much, I'm looking forward to it. I put a good trigger in it, much better than the one in my AR15. That alone might make it more fun. I can't imagine humping that thing on the trail or in the hills tho. Whew that would get old. Appreciate the thoughts, thanks.

They are better for packing in to a spot and sitting, versus carrying around, for sure. One I have was 7.6lbs naked, which isn't terrible when compared to basic bolt action sporter, but fully rigged out with a can, full mag, NV optic and illuminator, etc. and it gains right at 5lbs.

For sure. I can tell you if my pickup isn't going someplace, this rifle isn't either.

buy some boxes of various match 308 ammo and see what she likes. then buy lots of whatever the gun likes and is cheapest/easiest to find.

Winchester gray box soft point hunting ammo is relatively inexpensive shoots great and you can find it most places.