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kayjaygee_13

Issues with Aero Precision build

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Hey there!

I am going to preface this by saying that I am completely new to this, so please bear with me if I need more clarification on some of the terms and phrases that you guys use. Being a novice, I decided to go with the following components made by Aero Precision and figured hopefully I knew enough to put together a functional .308 rifle:

- M5 Complete Lower Receiver w/ MOE® Grip & Fixed Rifle Stock (https://www.aeroprecisionusa.com/m5-complete-lower-receiver-moe-grip-fixed-rifle-stock)
- M5E1 Enhanced 20" .308 CMV Complete Upper Receiver (https://www.aeroprecisionusa.com/m5e1-308-20in-cmv-complete-upper)
- .308 / 7.62 Bolt Carrier Group, Complete - Phosphate (https://www.aeroprecisionusa.com/308-bolt-carrier-group-phosphate)
- AR 308 Charging Handle (https://www.aeroprecisionusa.com/ar308-charging-handle)
- Magpul PMAG® 20-round Non-Window M3 LR-308 - Black (https://www.aeroprecisionusa.com/magpul-pmag-20-round-308-black)

It turned out I was wrong. I first tested the rifle with 150 grain Remington UMC 308 Win ammunition and fired 17 rounds and every spent casing failed to eject. I ran several tests with just a single round in the magazine and each and every time, the BCG failed to eject the spent casing and failed to lock back on the empty magazine. When the gun was tested with a few rounds loaded in the magazine, it failed to eject the spent casing and it had to be done manually via the charging handle. In fact, the last time I fired the gun with a single Remington round in the magazine, the spent casing was stuck in there so tightly that I had to use the "mortaring" tip I found on YouTube and I had to slam the stock to clear it.

Figuring that I might have better luck with different ammunition, I tested the gun with a single round of 168 grain Federal Gold Medal Sierra Match King 308 Win ammunition and the gun functioned in the same manner as with the Remington ammunition. The spent casing was not ejected and the bolt failed to lock back on the empty magazine. I loaded 5 rounds into the magazine and again each time, the spent casings had to be manually ejected via the charging handle. I should mention that I did clean and generously lubricated the gun before testing it with the Federal ammunition.

So I opened a ticket with Aero Precision and they suggested removing one O-ring from the extractor and testing again. I haven't had a chance to see if that would resolve these issues and I figured that I would post here in the meantime to see if you guys had any more suggestions. Thank you in advance!

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Just a shot in the dark but could you give us measurements on your recoil system? Spring, buffer- weights and the length?

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Maybe gas block alignment issues. Easy to check, slide the gas block forward and look for a shadow around the gas port on the barrel, port should be centered in the shadow.

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9 hours ago, kayjaygee_13 said:

So I opened a ticket with Aero Precision and they suggested removing one O-ring from the extractor and testing again. I haven't had a chance to see if that would resolve these issues and I figured that I would post here in the meantime to see if you guys had any more suggestions. Thank you in advance!

You don't have an extraction issue - leave the two o-rings in there.  Don't mess with them just yet. 

Lube.  How much lube was on the BCG and internals of the upper receiver when you fired this rifle?    Did you break down the BCG, remove the bolt, lube the gas rings on the bolt tail?  How many rounds total down the barrel so far?  You need to be able to shoot enough to seal the gas block to the barrel, gas tube to the gas block, with carbon fouling - to create a total gas seal there.  If you were running this gun dry, that will be a painful process.  This sounds like a gas problem...

4 hours ago, edgecrusher said:

Just a shot in the dark but could you give us measurements on your recoil system? Spring, buffer- weights and the length?

Rifle recoil system - that hardly ever gets screwed up, by any manufacturer.  Worth looking into the buffer length, though.  5.200" is the length for the .308AR buffers, 5.900" is the length you'll see if an AR15 buffer was accidentally put in there - which could create this issue...

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Thank you edgecrusher, jtallen83, and 98Z5V for your suggestions.

I did not check the gas block alignment because I'd rather not dismantle the upper, especially since Aero has mentioned that I might have to send it back to them in case the issues persisted after testing it with one less O-ring.

Here is the information about the recoil system: buffer length of 5 5/16 in, spring length of 12.75 in and it has 39 coils.

I took it to the range today and it was frustrating yet again. I managed to fire a meager 7 rounds of 168 grain Federal Gold Medal in between firing my other guns because none of the spent casings ejected and two of the casings had to be "mortared" out. In fact, the bolt did not move at all (I have it on video)! Also, I found it strange that the spent casings were almost cold to the touch, mere seconds after ejection! The rifle was cleaned and lubricated before taking it to the range, just like the last time, and the BCG was taken apart and cleaned and lubed as well. The only component that I did not dismantle was the ejector and the ejector spring. Admittedly, I did not shoot a lot of rounds (mainly due to frustration), but I fired with and without the second O-ring, with the same results. Absolutely no bolt movement and cool spent casings!

98Z5V, to answer your questions, I run it wet and take apart the BCG, except for the ejector and ejector spring, and squirt CLP until it's almost dripping. With all the issues with this gun, I have managed to fire about 30 rounds in total and I apologize if I come across as impatient for complaining when I have so few rounds down the barrel. But the last month or so has been a learning process and it has been frustrating, but interesting.

Thank you again for the help and I look forward to your suggestions.

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Without dismantling the upper; there are a few things you could look at and try...

First; remove the BCG and inspect the gas tube (take a picture and post it if you can). I am curious to know how dirty it is. You've only fired a few rounds, but there should be carbon visible if any gas is getting that far. 

@washguy explains this very well; but you can perform a blow test to see if your gas port, gas block, and gas tube are all open (pretty sure they aren't; but you would know from the carbon build up). In your case I would consider using a spent casing to plug up the chamber; grip the muzzle device to seal the gaps, and blow in the business end of the barrel (while holding the cartridge in the chamber with your finger). If you can blow air out the gas tube this way; then at least you know the passages at least pass gas. 

Beyond that; I suppose the cam pin could be failing to rotate for some reason. That could be an upper or BCG issue. I had to round the edges of the cam pin on my 308 build; not much, but it kept them from catching in the upper.

Photograph anything you can; even if you do end up sending it back... These problems are a curiosity for many of us around here; and there are plenty of people who could walk you through a solution once the problem is identified.

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1 hour ago, kayjaygee_13 said:

(1)Thank you edgecrusher, jtallen83, and 98Z5V for your suggestions.

(2) Here is the information about the recoil system: buffer length of 5 5/16 in, spring length of 12.75 in and it has 39 coils.

(3) 98Z5V, to answer your questions, I run it wet and take apart the BCG, except for the ejector and ejector spring, and squirt CLP until it's almost dripping. With all the issues with this gun, I have managed to fire about 30 rounds in total and I apologize if I come across as impatient for complaining when I have so few rounds down the barrel.\

 

1. Thank you for the Thank you.  We will solve this.  :thumbup:

2.  Are you absolutely positive on that buffer length?  That's 5.313", and it's too damn long.  .308AR Rifle Buffers are 5.200" long, so that's an extra hundred thou + that's screwing you up, right off the bat, and that DOES affect cycling.  I have a solution to solve this quickly, and at least test the rifle.  If it's truly 5.313" long, sand that bastard down to 5.200" long (or file it).  Attack that poly bumper on the end of it.  If it cycles after that - get a new buffer that's the correct length.  For now, don't even worry about that spring...  I'll address that spring if we can solve the function of the rifle, first.

3.  Good - run it WET.  I'm talking about almost dripping-wet, too.  .308ARs need ALOT of lube to break in and function.

Lastly - will you measure the internal depth of your receiver extension for me?  Measure at the top part of the extension, not the base, where the buffer retainer pin is.  Top, only - that's the only thing that counts.  Stick a tape measure down that until it bottoms out, grab the measurement at the end of the extension - and the extension should be flush with the top of the lower receiver ear.  If it's less than flush, it's not screwed in all the way, and we can address that, too.  You should see a measurement of exactly 9 11/16".  Not more, not less.  Right on the money.

Lemme know...

Edited by 98Z5V

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15 minutes ago, Lane said:

Beyond that; I suppose the cam pin could be failing to rotate for some reason. That could be an upper or BCG issue. I had to round the edges of the cam pin on my 308 build; not much, but it kept them from catching in the upper.

What upper receiver did you use in your build?...

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1 hour ago, kayjaygee_13 said:

the bolt did not move at all

This is what lead me to ask about those things...

7 minutes ago, 98Z5V said:

What upper receiver did you use in your build?...

My upper is not Aero; it was that Ceratac we had so much fun with. Just looking at the facts in this case, and it sounds like "no gas"; but could be a bit more complicated. How many things can keep the BCG from moving at all?

Edited by Lane
group

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4 minutes ago, Lane said:

My upper is not Aero; it was that Ceratac we had so much fun with.

The cam pin cutout is not in the right place, if you had to round the edges of your cam pin to get the bolt into battery.  The better option would have been to take material from the rearward edge of the cam pin cutout, to get the cam pin to clear it.  There's plenty of meat in the upper there, to do that.

Edited by 98Z5V

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1 minute ago, 98Z5V said:

The cam pin cutout is not in the right place, if you had to round the edges of your cam pin to get the bolt into battery.

My problem wasn't going into battery; I think I only noticed it cycling the bolt without a round in the chamber.

But in regards to this @kayjaygee_13 problem; I can't think of many other things at play if the BCG doesn't move at all.

 

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36 minutes ago, Lane said:

I can't think of many other things at play if the BCG doesn't move at all.

 

He never stated his BCG doesn't move at all - he only stated that spent brass isn't getting out of the gun.  First culprit is the BCG length, and that's the quickest thing to solve, by cutting down the poly bumper on the end of it, until that buffer assembly is 5.200" long.   :thumbup:

The extractor setup isn't the issue, as AP told him - those dual o-rings provide some SERIOUS force on the extractor, and I can say it works, well, myself.  The brass isn't getting out of the gun because the BCG is too long - right now, pending internal depth on the rifle receiver extension.  The BCG isn't cycling far enough, and screwing everything up - IF the extension is 9 11/16" internal depth, and screwed in all the way...

Edited by 98Z5V

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2 hours ago, kayjaygee_13 said:

I managed to fire a meager 7 rounds of 168 grain Federal Gold Medal in between firing my other guns because none of the spent casings ejected and two of the casings had to be "mortared" out. In fact, the bolt did not move at all (I have it on video)!

You need to post/host that vid of the BCG not moving, as well as get pics of your brass up, in this thread... 

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Video would be great. So many variables to this. 

I had a palmetto bcg be an issue in a ar15 do to a gas key not be tight and staked properly. Bcg didnt cycle or extract from lack of gas. Just one more idea and area to inspect.

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I will post pictures of the casings and respond to the queries soon, but here is the video in the meantime. I apologize that the quality isn't exactly the best.

Thank you Lane, 98Z5V, Chuck Plissken, and 08sniper! I sincerely appreciate your help and suggestions.

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If your not going to disassemble and in spect I would go ahead and send it back and not shoot it anymore. We might not know the reason if you send it back they will just fix or replace with no explanation 

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