Building an Aero Precision 308 from parts

View · by **BigBlue** on Sun Mar 18, 2018 12:36 pm

As folks may have seen in my recent thread Suggestions for parts - 308 AR build I decided to build a quality AR308 myself. Initially I was looking to buy a complete upper and lower as a way to get good components and save some dollars compared to a complete weapon. I had found a sweet Daniel Defense 308 that had all the features I wanted and was done in beautiful desert camo. But at near $3000 it was not happening. A good fellow at the gun store where I found that mentioned the upper/lower stuff from Aero Precision. My research into them backed up that they have quality stuff. Certainly not going to call things a bargain but at roughly half the price of the DD for similar features and respected quality I was interested. Shortly after that I found their February builder kit special that included only a stripped upper, lower and handguard. The thought of locating everything needed and assembling from scratch was a bit scary because I had not messed with installation of a barrel or gas system before. After more research it turns out this isn't rocket science and I decided to just go for it. Thanks to folks who helped me out in that prior thread.

Now that I've acquired all of the parts I went ahead and put everything together this weekend. Couldn't really have gone any smoother. I think it really helped that I stuck with most of the internal pieces from Aero. As you may or may not know, 308 AR rifles are not nearly as standardized as AR15s. There are several variations in basic style and multiple unique things per manufacturer within the styles. This is why sticking with mostly Aero stuff seemed wise. That, plus the quality.

So, at the end of the week I had amassed a large pile of parts:

These parts included:

So I started with the upper and barrel. Clamped the upper in the vice and attached Aero's unique barrel nut at 65 ft-lbs after greasing the barrel extension and barrel nut threads. One of the unique features of Aero's enhanced M5E1 308 upper is that the attachment for the handguard is machined right into the upper. The barrel nut is male threaded and threads inside the handguard support area.

* Don't laugh at my vice (or do, I don't care). I think it was cast by blind children in China after their bedtime one night and then they slapped on some auto body filler and painted it to make it look nice. Obviously the filler hasn't held up to years of doing what you do to stuff in a vice.

After the barrel went on without drama I attached the gas tube and gas block. Used some tips from YouTube videos to make sure the block was aligned correctly with the gas port and spaced correctly. Pinned the tube to the gas block without incident using a simple roll pin starter I made from a small lag bolt with the threads ground down and end flattened and then a hole drilled in the end. Love $0 tools! Thanks to whatever YT video showed me that tip.

And then the free-float handguard bolted up very quickly. No alignment needed.

Next it was back in the vice for the muzzle device. This went on simply but I have a question about it that I'll add in a following post.

Time to move on to the lower now. Opened up Aero's enhanced lower parts kit and tried to figure out what every part was. Didn't manage to figure them all out so I just started putting stuff together. Another good YT video made this easy.

First up was the mag release:

Then came the trigger parts, safety and retention pins for the pivot and takedown pins. Plus the grip.

Followed by the buffer tube, stock, buffer retainer and buffer itself.

Not much left at this point. Just had to put the charging handle and BCG into the upper and pin the upper to the lower. Look, a complete toy!

Thoughts to follow...

View · by **BigBlue** on Sun Mar 18, 2018 12:44 pm

So what I learned is that assembling an AR308 is fairly easy provided you have parts that work together. And now that I've done everything I'd have no reluctance to assembling an AR15 either. I already owned a torque wrench. I bought a simple armorer's kit for the barrel nut wrench and castle nut on the buffer tube. It came with vice blocks. For the $25 I spent on that it was a worthwhile investment compared to bringing the upper & barrel to a gun shop and paying them to install it.

Aero Precision makes some nice stuff. Everything fit together just like it should. All parts were included. I'm no AR expert but this looks like good quality stuff and my research into Aero backs that up.

I'll need to choose an optic in the future when the budget recovers. I also have a LaRue trigger on order that I will swap in some day.

The only part I'm really still not sure about is the muzzle device attachment. When I threaded it on by hand it ended up needing only about 1/4 rotation (90*) to get it lined up with the ports on top and the logo on the bottom, as it is supposed to be. This didn't take a ton of torque and I don't think it crushed the crush washer much. However, at this point I didn't really feel like it would be the best choice to try to rotate it another full 360* to really get it tight. So, did I do something wrong? Should I remove it and try to re-clock it so it starts threading 180* from where it started this time? If that was possible then it would end up needing the wrench for about 270* instead of 90*. Or is the crush washer so soft that I can easily rotate this the required 360* from where it is to crush it and get better torque?

As far as I know I should have a fully functioning rifle at this point. My research says there is no need to headspace the bolt. I've verified the function of the BCG, trigger and safety. I know I'll have to make initial and fine-tuning adjustments to the gas block too. Anything else I'm missing before I take it out with some lead?

Thanks!
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View · by **Ghost** on Sun Mar 18, 2018 1:59 pm

Nice write up and nice rifle. Glad you chose to do it yourself.

As far as muzzle devices. The ones I’ve done all had shims if they needed a specific orientation, shim it until it lines up. Do you think you can get another revolution of crush on it? Any idea on how much you torqued it?

View · by **BigBlue** on Mon Mar 19, 2018 7:09 am

Ghost wrote:Nice write up and nice rifle. Glad you chose to do it yourself.

As far as muzzle devices. The ones I’ve done all had shims if they needed a specific orientation, shim it until it lines up. Do you think you can get another revolution of crush on it? Any idea on how much you torqued it?

Thanks. The Gamma did not come with shims, just a single crush washer (cone shaped). I didn't end up torquing it much at all to get it to the current position. But I get the feel that it would take a lot to spin it another 360*. But if the crush washer gives a lot then maybe that wouldn't be as bad as I think. I may call VG6 Precision and ask them for their advice.

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View · by **INOR** on Mon Mar 19, 2018 8:37 am

Cool build. Thanks for sharing some pics and your process. Nice job!

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View · by **Holland&Holland** on Mon Mar 19, 2018 8:45 am

And so the addiction begins!

Welcome to the club

View · by **Ghost** on Mon Mar 19, 2018 9:34 am

Holland&Holland wrote:And so the addiction begins!

Welcome to the club

Good point

BigBlue, what are you going to build next?

View · by **BigBlue** on Mon Mar 19, 2018 11:01 am

Ghost wrote:
Holland&Holland wrote:And so the addiction begins!

Welcome to the club

Good point

BigBlue, what are you going to build next?

Fortunately (or not) I have incredible restraint. It's called my wallet. :-)

Actually, with the addition of this 308 it really rounded out the holes in my wish list. At present there is nothing that I have a strong desire to add. About the only areas where I may continue the build would be as some of the relation gets to adulthood and could use their own MSRs. We'll see...

What I really need now is to focus time on using what I have. I need to keep my marksmanship tuned up, especially with handguns.

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View · by **Holland&Holland** on Mon Mar 19, 2018 12:18 pm

BigBlue wrote:
Ghost wrote:Nice write up and nice rifle. Glad you chose to do it yourself.

As far as muzzle devices. The ones I’ve done all had shims if they needed a specific orientation, shim it until it lines up. Do you think you can get another revolution of crush on it? Any idea on how much you torqued it?

Thanks. The Gamma did not come with shims, just a single crush washer (cone shaped). I didn't end up torquing it much at all to get it to the current position. But I get the feel that it would take a lot to spin it another 360*. But if the crush washer gives a lot then maybe that wouldn't be as bad as I think. I may call VG6 Precision and ask them for their advice.

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I would call them, yes the crush washer does need to crush to be effective but hard to tell without looking at it where you are at in that. With breaks that need timed like this I usually use peel washers or shims and about 20 - 25 ft lbs max.

View · by **Holland&Holland** on Mon Mar 19, 2018 12:20 pm

BigBlue wrote:
Ghost wrote:
Holland&Holland wrote:And so the addiction begins!

Welcome to the club

Good point

BigBlue, what are you going to build next?

Fortunately (or not) I have incredible restraint. It's called my wallet.

Actually, with the addition of this 308 it really rounded out the holes in my wish list. At present there is nothing that I have a strong desire to add. About the only areas where I may continue the build would be as some of the relation gets to adulthood and could use their own MSRs. We'll see...

What I really need now is to focus time on using what I have. I need to keep my marksmanship tuned up, especially with handguns.

BB

We shall see. Now that you will be getting their emailed sales flyer for every sale. It always seem that I do not need another one, it is just I end up with enough parts that it does not seem too far fetched to build it.

View · by **BigBlue** on Mon Mar 19, 2018 1:00 pm

Holland&Holland wrote:I would call them, yes the crush washer does need to crush to be effective but hard to tell without looking at it where you are at in that. With breaks that need timed like this I usually use peel washers or shims and about 20 - 25 ft lbs max.

Tried to call but they were 'busy'. I did chat with their support after realizing that VG6 Precision is now a part of Aero Precision. Their rep wasn't a ton of help. Based on my description (hand tight, then 1/4 turn by wrench, washer not really crushed) she said it sounded fine, but when asked for more detail she said "You tighten hand tight, and then torque a full 360 with the wrench", which is quite different. I suppose if the expectation is that 360* after hand tight is normal then another 90* probably won't wreck anything. I'll take it back off and lube up the washer surfaces well and go at it again. If I get to the 25 ft-lbs and it is not close to straight then I can get a shim kit.

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View · by **Holland&Holland** on Mon Mar 19, 2018 3:30 pm

BigBlue wrote:
Holland&Holland wrote:I would call them, yes the crush washer does need to crush to be effective but hard to tell without looking at it where you are at in that. With breaks that need timed like this I usually use peel washers or shims and about 20 - 25 ft lbs max.

Tried to call but they were 'busy'. I did chat with their support after realizing that VG6 Precision is now a part of Aero Precision. Their rep wasn't a ton of help. Based on my description (hand tight, then 1/4 turn by wrench, washer not really crushed) she said it sounded fine, but when asked for more detail she said "You tighten hand tight, and then torque a full 360 with the wrench", which is quite different. I suppose if the expectation is that 360* after hand tight is normal then another 90* probably won't wreck anything. I'll take it back off and lube up the washer surfaces well and go at it again. If I get to the 25 ft-lbs and it is not close to straight then I can get a shim kit.

BB

Remember the crush washer is a one and done application. What torque are you to now if you try going further?

View · by **BigBlue** on Mon Mar 19, 2018 6:45 pm

Well the torque wrench won't easily fit the armorer's wrench because the 1/2" drive hole is very close to the wrench part that is used for the Gamma. I'll see if I can use a short extension to fix that. Either that or find the right size crowfoot wrench instead of the armorer's wrench.

All I know is that it didn't take too much to rotate it the first 90* but I didn't feel right going another 360* without at least asking about it...

Later today tech support called me back (from the message I left when the phones were busy earlier) and said the right way is: hand tight, torque to 35 ft-lbs, then continue turning to clock it to the correct orientation. That tells me I should be fine continuing with the plan.

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View · by **TommyMN** on Wed Apr 04, 2018 6:53 pm

So is the 308 carbine buffer tube the same as a carbine ar15 tube?

View · by **BigBlue** on Wed Apr 04, 2018 10:19 pm

TommyMN wrote:So is the 308 carbine buffer tube the same as a carbine ar15 tube?

In my research I don't think I ever saw a distinction between AR15 and AR10 (308) gas tubes. In fact, the Aero gas tube product page says: "Stainless Steel Gas Tube for AR15 & AR10 rifles".

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