Need help!! Aero m5e1 not cycling

[AH 64 Apache]

Hello. I recently put together an Aero Precision m5e1 chambered in .308 win.
It has an 18" barrel with a rifle length gas tube. Mil spec carbine lower.
The upper I bought complete and I put together the lower. Everything is Aero.
It fires and ejects properly but it won't pick up a new round. My only thought is that a rifle length gas tube and carbine buffer don't work together, although I've read differently. As you can tell I don't know much about ARs, so any suggestions will be appreciated. Thanks

 

[n2ishun]

Remove upper and remove bolt, put foam earplug in chamber and with your lips blow thru muzzle.
How much air goes thru gas tube ?
Explain complete buffer group (buffer, spring, tube).
What mags ?

 

[2aBaC̶a̶]

What buffer and spring? How long is your buffer tube?

 

[AH 64 Apache]

Not sure about the buffer group I bought it off Aero.

M5 .308 Carbine Buffer Kit

Shop M5 .308 Carbine Buffer Kit, No Stock and more online at aeroprecisionusa.com. Free shipping on all orders over $99.

www.aeroprecisionusa.com

The buffer is 2.5" and weighs 3.8 oz
The tube's outside length is 7 7/32"

 

[AH 64 Apache]

I did what you you said with the ear plug and there is definitely air getting through. But i'm not sure how to quantify it.

Magpul pmag 10 LR/SR gen m3

 

[hafejd30]

Try another mag?

 

[Steel head]

Sounds like it’s short stroking
Did you put the gas block on or was it a built upper?
What ammo and did you try other ammo?
You could try a lighter buffet or spring.

 

[AH 64 Apache]

It was built on the upper. It was the cheapest ammo I could find, so maybe that could be part of the prob

 

[2aBaC̶a̶]

Try some different ammo. And lube the bcg. If that doesnt work try a lighter buffer and or spring.

 

[AH 64 Apache]

Will do. Does a lighter spring mean shorter? And do you have any recommendations

 

[n2ishun]

Usual 308 buffer weight is about 5.4-5.8 ounces but if it's short stroking (it seems everyone is agreeing with this) this won't be the issue.
I ALWAYS run a A5 type buffer tube on a 308...it's 3/4 of an inch longer give or take a tad and helps more than I could ever say.
The 308 bolt is longer than a 556 bolt so it helps having a bit more to play with....that bolt also has to come back farther to accommodate the longer 308 round.
You need that 3/4 inch.
Vltor makes the tube, maybe get a Tubbs or Wolff buffer spring to go with it and a real (5+ ounce) 308 buffer...2.5 inch long is correct.
Don't use 5.56 shit on a 308, they ain't the same.
The simple test is the charging handle pull, it should not be all that hard to pull back and you should not be able to max out movement with the handle, should still be about an inch rearward motion of the bolt possible.
(I hope that's understandable).

 

[wade2big]

Usual 308 buffer weight is about 5.4-5.8 ounces but if it's short stroking (it seems everyone is agreeing with this) this won't be the issue.
I ALWAYS run a A5 type buffer tube on a 308...it's 3/4 of an inch longer give or take a tad and helps more than I could ever say.
The 308 bolt is longer than a 556 bolt so it helps having a bit more to play with....that bolt also has to come back farther to accommodate the longer 308 round.
You need that 3/4 inch.
Vltor makes the tube, maybe get a Tubbs or Wolff buffer spring to go with it and a real (5+ ounce) 308 buffer...2.5 inch long is correct.
Don't use 5.56 shit on a 308, they ain't the same.
The simple test is the charging handle pull, it should not be all that hard to pull back and you should not be able to max out movement with the handle, should still be about an inch rearward motion of the bolt possible.
(I hope that's understandable).

He has a carbine buffer tube and a shorter buffer to allow for the longer .308 bcg. This isn’t his problem.

 

[the monk]

How many rounds do you have through it?

Try different good quality ammo with a different magazine. Also really lube the bcg, often times the gas rings and the bcg need to wear in. Generally this is not an issue if properly lubed. Good video on where to lube:

 

[2aBaC̶a̶]

Does the bolt stay open on bolt catch on the last round? Or does the bcg catch on the mag? Or does it not cycle enough to stay open?

 

[RUTGERS95]

Does the bolt stay open on bolt catch on the last round? Or does the bcg catch on the mag? Or does it not cycle enough to stay open?

this, then let's diagnose

 

[AH 64 Apache]

⁹

Usual 308 buffer weight is about 5.4-5.8 ounces but if it's short stroking (it seems everyone is agreeing with this) this won't be the issue.
I ALWAYS run a A5 type buffer tube on a 308...it's 3/4 of an inch longer give or take a tad and helps more than I could ever say.
The 308 bolt is longer than a 556 bolt so it helps having a bit more to play with....that bolt also has to come back farther to accommodate the longer 308 round.
You need that 3/4 inch.
Vltor makes the tube, maybe get a Tubbs or Wolff buffer spring to go with it and a real (5+ ounce) 308 buffer...2.5 inch long is correct.
Don't use 5.56 shit on a 308, they ain't the same.
The simple test is the charging handle pull, it should not be all that hard to pull back and you should not be able to max out movement with the handle, should still be about an inch rearward motion of the bolt possible.
(I hope that's understandable).

Thankyou for the advise but I think wade2big is right and thats not my prob.


As soon as I get a chance I'm gonna lube the ×÷=÷× out of it and try some quality Ammo.

Does the bolt stay open on bolt catch on the last round? Or does the bcg catch on the mag? Or does it not cycle enough to stay open?

I have not shot to the last round yet honestly I've only shot two rounds through it!! After it wouldn't reload, I knew something wasn't right, so I stopped shooting it.

When I manually use the charging handle it locks open on an empty mag.....?

 

[hafejd30]

⁹

Thankyou for the advise but I think wade2big is right and thats not my prob.


As soon as I get a chance I'm gonna lube the ×÷=÷× out of it and try some quality Ammo.


I have not shot to the last round yet honestly I've only shot two rounds through it!! After it wouldn't reload, I knew something wasn't right, so I stopped shooting it.

When I manually use the charging handle it locks open on an empty mag.....?

What he’s saying is load one round into the magazine and fire the gun. A properly tuned gas gun should have about a 3 O’clock ejection and lock the bolt back on the empty Mag. If the bolt closes without locking back it’s short stroking and not allowing the bolt to come far enough to the rear when fired

 

[n2ishun]

Why have 2 people now mis-read what I typed ?
Is literacy really that bad these days ?
Here...lemme bold, underline, AND italic this for the ones that didn't get all their skoolin's in.

Usual 308 buffer weight is about 5.4-5.8 ounces but if it's short stroking (it seems everyone is agreeing with this) this won't be the issue.

I really shouldn't have to do that.
BTW, pouring oil on it won't do diddly squat.

 

[the monk]

BTW, pouring oil on it won't do diddly squat.

I disagree, I have seen numerous guns that are brand new (factory & home builds) that were not lubed properly and had issues for the first 20 rounds or so. He only has 2 rounds through it. Troubleshooting always starts at the very beginning (it is clear he is a beginner with an AR), if not you will run around in circles.

 

[msgriff]

Usual 308 buffer weight is about 5.4-5.8 ounces but if it's short stroking (it seems everyone is agreeing with this) this won't be the issue.
I ALWAYS run a A5 type buffer tube on a 308...it's 3/4 of an inch longer give or take a tad and helps more than I could ever say.
The 308 bolt is longer than a 556 bolt so it helps having a bit more to play with....that bolt also has to come back farther to accommodate the longer 308 round.
You need that 3/4 inch.
Vltor makes the tube, maybe get a Tubbs or Wolff buffer spring to go with it and a real (5+ ounce) 308 buffer...2.5 inch long is correct.
Don't use 5.56 shit on a 308, they ain't the same.
The simple test is the charging handle pull, it should not be all that hard to pull back and you should not be able to max out movement with the handle, should still be about an inch rearward motion of the bolt possible.
(I hope that's understandable).

Your posts have some facts mixed in with a lot of misinformation.

 

[mtrmn]

Be sure to not just put oil ON the BCG, but put lots of oil IN it. On the gas rings.

 

[n2ishun]

Your posts have some facts mixed in with a lot of misinformation.

Go ahead and point out any misinformation I might have posted.
I'm dying to see it.

 

[msgriff]

Go ahead and point out any misinformation I might have posted.
I'm dying to see it.

As to not derail the thread, I will point out one of many errors or your part, then I will no longer reply to your posts.

"n2ishun said:
Usual 308 buffer weight is about 5.4-5.8 ounces but if it's short stroking (it seems everyone is agreeing with this) this won't be the issue.
I ALWAYS run a A5 type buffer tube on a 308...it's 3/4 of an inch longer give or take a tad and helps more than I could ever say.
The 308 bolt is longer than a 556 bolt so it helps having a bit more to play with....that bolt also has to come back farther to accommodate the longer 308 round.
You need that 3/4 inch.
Vltor makes the tube, maybe get a Tubbs or Wolff buffer spring to go with it and a real (5+ ounce) 308 buffer...2.5 inch long is correct.
Don't use 5.56 shit on a 308, they ain't the same.
The simple test is the charging handle pull, it should not be all that hard to pull back and you should not be able to max out movement with the handle, should still be about an inch rearward motion of the bolt possible.
(I hope that's understandable)."

For large frames, the Vltor A5, or intermediate length, receiver extension uses a standard AR-15 buffer which is 3.25" long.

 

[n2ishun]

I guess it doesn't work in either my mega monolithic build or my aero m5e1 build.
Crap, I better go change them now huh ?

 

[RUTGERS95]

you don't need the a5 buffer tube, simple AR15 carbine buffer tube, 308 carbine buffer and 308 carbine buffer spring.

 

[troupe]

That is it Does not have to be a special buffer tube, but the buffer and spring are specific.

 

[Charger442]

how far does it throw the brass? a long ways or barely out of the gun? when you fire a round, and you pull the mag out, do you have marks on the next round? i would say probably half the case length?


ive seen many an AR barrel that needed to have the gas port opened up. what type of gas block is it? can you easily remove it to check the gas port? also, who built the upper, did it come directly from aero?

 

[Pappasniper]

My man, it sounds like the gas tube might be chocking off the gas hence under gassed. However, if its overgassed, the magazine can't push the round up fast enough for BCG to catch the round, ie overgassed. That wold be a more palatable explanation. Hence heavier Buffer and spring.

How does the brass get thrown when you shoot the gun, very hot and violent, or does it just lob the brass at 3:30? If its hot and slamming brass its over gassed. Do your test then if we need we can :

Then we can go back to under gassed

PB

 

[Steve_In_29]

Usual 308 buffer weight is about 5.4-5.8 ounces but if it's short stroking (it seems everyone is agreeing with this) this won't be the issue.
I ALWAYS run a A5 type buffer tube on a 308...it's 3/4 of an inch longer give or take a tad and helps more than I could ever say.
The 308 bolt is longer than a 556 bolt so it helps having a bit more to play with....that bolt also has to come back farther to accommodate the longer 308 round.
You need that 3/4 inch.
Vltor makes the tube, maybe get a Tubbs or Wolff buffer spring to go with it and a real (5+ ounce) 308 buffer...2.5 inch long is correct.
Don't use 5.56 shit on a 308, they ain't the same.
The simple test is the charging handle pull, it should not be all that hard to pull back and you should not be able to max out movement with the handle, should still be about an inch rearward motion of the bolt possible.
(I hope that's understandable).

No you do NOT.

You just need to run the right combo of buffer and spring.

Both my rifles have 7" tubes and function fine with a KAW Valley 5.6oz 2.5" buffer and KAW Valley .308 carbine spring.

The 7.75" tube simply allows for the use of an even heavier buffer if desired.

 

[ichigo]

you probably need to break in your rifle. lube your bcg were it contacts with the upper (gas key area, underneath were it contacts with the bolt catch, some on the cam pin and part of the bolt) but not in the bolt face. load one round and send it, observe the ejection location of the brass and if the bolt is caught by bolt catch. If loading one was a success, load 2 rounds and send the 1st round and observe if the brass is ejected and the 2nd round is loaded/chambered.

If the ejection of the brass is in 1-3 o'clock (sign of overgassed), 4:30-6 o'clock (sign of short stroke).

 

[wade2big]

No you do NOT.

You just need to run the right combo of buffer and spring.

Both my rifles have 7" tubes and function fine with a KAW Valley 5.6oz 2.5" buffer and KAW Valley .308 carbine spring.

The 7.75" tube simply allows for the use of an even heavier buffer if desired.

I didn’t know there were heavy buffers for the carbine length receiver extensions. Good to know.

 

[5pins]

I would check and make sure they put in the right length gas tube. There are two different AR-10 rifle length tubes. I ran across a similar problem with a midlenght build.

Gas Tubes for 308 AR-Style Rifles

If you're doing a 308 build you have to navigate a few tricky compatibility issues. You've got to figre out whether your barrel uses the older Armalite AR-10 length gas length, or the more modern DPMS spec. On Armalite AR-10 pattern builds, the gas journa

truenortharms.com

 

[mtrmn]

No you do NOT.

You just need to run the right combo of buffer and spring.

Both my rifles have 7" tubes and function fine with a KAW Valley 5.6oz 2.5" buffer and KAW Valley .308 carbine spring.

The 7.75" tube simply allows for the use of an even heavier buffer if desired.

Not disagreeing by any means, just adding some important info.

The 7.75" tube REQUIRES the use of the 3.25" buffer (AR15-carbine-length), whether heavier or not. Use of a 2.5" buffer in this 7.75" tube will cause the BCG to over-travel and hit the threaded portion of the lower receiver.

The H3 AR15 3.25" buffer weighs somewhere around 5.3 oz, the same weight as needed for 308.

Personally I also use the KAW 5.6oz buffer, with a Sprinco Orange spring with excellent results.

 

[Steve_In_29]

Not disagreeing by any means, just adding some important info.

The 7.75" tube REQUIRES the use of the 3.25" buffer (AR15-carbine-length), whether heavier or not. Use of a 2.5" buffer in this 7.75" tube will cause the BCG to over-travel and hit the threaded portion of the lower receiver.

The H3 AR15 3.25" buffer weighs somewhere around 5.3 oz, the same weight as needed for 308.

Personally I also use the KAW 5.6oz buffer, with a Sprinco Orange spring with excellent results.

Yes agreed. I wasn't clear enough about that in my post.

 

[AH 64 Apache]

Thankyou all for your post's.
I plan to try all the tests today.
If I remember correctly the shells ejected around 3:00
Also my buffer tube is 7" measured on the inside.

Fyi I'm only 15 and I haven't exactly done all my "scoolins"

 

[quiksilv81]

Check the gas port size on the barrel. Sometimes the ballistic advantage barrels port holes are a tad undersized. Had to have my gunsmith open mine up on my 6.5 creed. Now it runs great with no issues. Just something else to check. And yes before I had it drilled out I tried different buffers, springs nothing helped then I had my smith measure the port size and sure enough it was undersized.

 

[czgunner]

Hello. I recently put together an Aero Precision m5e1 chambered in .308 win.
It has an 18" barrel with a rifle length gas tube. Mil spec carbine lower.
The upper I bought complete and I put together the lower. Everything is Aero.
It fires and ejects properly but it won't pick up a new round. My only thought is that a rifle length gas tube and carbine buffer don't work together, although I've read differently. As you can tell I don't know much about ARs, so any suggestions will be appreciated. Thanks

I would recommend you correctly lube the BCG, try at least 2 more types of ammo and have another magazine brand on hand then go shoot a minimum of 20 rounds to see how things go.

 

[Tiribulus]

Check the gas port size on the barrel. Sometimes the ballistic advantage barrels port holes are a tad undersized. Had to have my gunsmith open mine up on my 6.5 creed. Now it runs great with no issues. Just something else to check. And yes before I had it drilled out I tried different buffers, springs nothing helped then I had my smith measure the port size and sure enough it was undersized.

My 16 in. carbine length BA barrel came with a port size of .053, which is too small. I opened it up to .065 and it completely fixed my undergassing/short stroking problem. I did try some other stuff first, but that gave me 100% reliability ever since. Drilling it out was pretty trivial actually if you have the tools and are pretty good with stuff like this.

 

[msgriff]

My 16 in. carbine length BA barrel came with a port size of .053, which is too small. I opened it up to .065 and it completely fixed my undergassing/short stroking problem. I did try some other stuff first, but that gave me 100% reliability ever since. Drilling it out was pretty trivial actually if you have the tools and are pretty good with stuff like this.

Just to clarify, what caliber/chambering?

 

[r.tenorio671]

Thankyou all for your post's.
I plan to try all the tests today.
If I remember correctly the shells ejected around 3:00
Also my buffer tube is 7" measured on the inside.

Fyi I'm only 15 and I haven't exactly done all my "scoolins"

....

 

[db2000]

Not disagreeing by any means, just adding some important info.

The 7.75" tube REQUIRES the use of the 3.25" buffer (AR15-carbine-length), whether heavier or not. Use of a 2.5" buffer in this 7.75" tube will cause the BCG to over-travel and hit the threaded portion of the lower receiver.

The H3 AR15 3.25" buffer weighs somewhere around 5.3 oz, the same weight as needed for 308.

Personally I also use the KAW 5.6oz buffer, with a Sprinco Orange spring with excellent results.

I also use 2.5” KAW 5.6oz but with Tubbs AR10 SS flat wire spring. I use an A2 rifle tube. SA AGB. No issues on Seekins SP10 w/ proof barrel and matched JP bolt.

 

[Tiribulus]

Just to clarify, what caliber/chambering?

Oh sorry. 556/223. Apparently this has been a thing with some of their barrels recently. I found some other folks who had undersized gas ports on theirs too. Maybe somebody set up the tooling wrong for a production run or something. Shouldn't have to do that, but to me it wasn't a big deal really. Took like 15 minutes. I didn't even take the barrel out of the receiver and it's been perfect ever since.

 

[bfoosh006]

For the OP, I would allow for a little more break in time.
I understand and respect your concerns... but don't worry, you aren't the first person to have NIB Large Frame AR issues.
Large Frame AR's tend to need more time for the parts to settle in.

After break in.. you can then consider heavier buffer weights , etc. if desired.

The RLGS on a 18" barrel can be a "little" short on gas volume / usage.
My 18" 5.56 RLGS barrels are fussy for the first 100rds... but do settle down after full power ammo break in.

And wise choice on staying with one manufacturer for the various parts.

And do lube it well.... be sure the chamber is clean of any packing oils, and lube the recoil spring as well ( not dripping wet ) disassemble the BCG, lube as normal. ( It could be your BCG was shipped sparsely with oil )

Aero uses a DPMS pattern buffer tube setup.
That means... a AR15 Carbine length buffer tube, with a 2.5" 308 carbine buffer, and a 308 Carbine length recoil Spring.

As a FWIW... the Armalite pattern buffer tube setup, uses a Vltor A5 length buffer tube ( about 3/4" longer internal depth ) to allow use of typical AR15 3.25" carbine buffers, and ( typically ) a Armalite EA1095 recoil spring.

The various parts, listed above... DO NOT INTERCHANGE..... Misunderstanding and Interchanging parts can cause a lot of issues.
As examples....
1. As mentioned, using the 2.5" buffer in a A5 / Armalite length carbine buffer tube can cause battering at the lowers RE threads.... and even if the lower doesn't get smacked / beat up... the additional excess recoil travel could cause bolt catch breakage, and other "odd" issues.
2. Using a 3.25" buffer in a AR15 carbine length buffer tube will cause short stroking.... because the to long buffer doesn't allow enough travel for the longer 308 BCG.... that means the bolt catch doesn't have enough clearance to function as designed.

And just for more info in context to buffer tubes and the Large Frame AR... A rifle length buffer tube setup, uses a standard AR15 rifle length buffer tube, with a 308 rifle length buffer ( 5.2" long , and shorter then a AR15 rifle length buffer, by that 3/4" ), is needed from the added 308 length / travel of the 308 BCG.

If you have any other questions... be sure to ask, many of us have gone through the same thing you are.

The lack of a "Mil-Spec" guideline for Large Frame AR's is a pita... we are spoiled by the AR15 Mil-Spec guidelines , Lol