Aero 308 build short cycling with slo mo video

[Bjj51]

weapon firing with one round in the magazine 

https://streamable.com/6rrpth

 

Gun specs 

Aero m5 upper/lower 

Stag10 20” heavy barrel w rifle length gas, vltor gas block 

Aero nitride bcg

A2 buffer , 12.5” spring (my friend said it’s an ar10 rifle length spring , this is the only part I’m not sure of), dpms branded ar10 5.4oz buffer, magpul fixed rifle length stock 

I’ve put about ~200 rounds through it , it had problems cycling at first and we realligned the gas block. Shot 50 rounds of mag tech m80 flawlessly. I took A break for 20 or so minutes and switched to ruag white box m80 and it seemed like it was short stroking like before we realligned the gas block (bolt won’t hold open with one round in mag, failure to feed , failure to eject , round getting halfway stuck exiting the chamber— I think This is called a stovepipe?). 

I gave It a quick wipe down with some napkins and dumped some clp on the bcg and it cycled fine for a mag then went back to the same thing. We took a video and it looked like it was ejecting at maybe 5 o’clock (hard to tell from the angle , definitely is not ejecting forward). 

At first I thought the ammo was the issue but the fact that it cycled briefly after a quick re lube makes me wonder if it just needs more lube / break in time(I cant Imagine the ruag m80 is THAT different from the Magtech m80 but I could Be mistaken). I’m going to clean it thoroughly and try some tetra lube heavily on the bcg next time I go Out. I would’ve tried the mag tech again but we were all out of it. 

Any thoughts / experiences would be greatly appreciated , this site has been a fantastic resource

 

 

[Matt.Cross]

On 12/21/2021 at 6:32 PM, Bjj51 said:

weapon firing with one round in the magazine 

https://streamable.com/6rrpth

 

Gun specs 

Aero m5 upper/lower 

Stag10 20” heavy barrel w rifle length gas, vltor gas block 

Aero nitride bcg

A2 buffer , 12.5” spring (my friend said it’s an ar10 rifle length spring , this is the only part I’m not sure of), dpms branded ar10 5.4oz buffer, magpul fixed rifle length stock 

I’ve put about ~200 rounds through it , it had problems cycling at first and we realligned the gas block. Shot 50 rounds of mag tech m80 flawlessly. I took A break for 20 or so minutes and switched to ruag white box m80 and it seemed like it was short stroking like before we realligned the gas block (bolt won’t hold open with one round in mag, failure to feed , failure to eject , round getting halfway stuck exiting the chamber— I think This is called a stovepipe?). 

I gave It a quick wipe down with some napkins and dumped some clp on the bcg and it cycled fine for a mag then went back to the same thing. We took a video and it looked like it was ejecting at maybe 5 o’clock (hard to tell from the angle , definitely is not ejecting forward). 

At first I thought the ammo was the issue but the fact that it cycled briefly after a quick re lube makes me wonder if it just needs more lube / break in time(I cant Imagine the ruag m80 is THAT different from the Magtech m80 but I could Be mistaken). I’m going to clean it thoroughly and try some tetra lube heavily on the bcg next time I go Out. I would’ve tried the mag tech again but we were all out of it. 

Any thoughts / experiences would be greatly appreciated , this site has been a fantastic resource

 

 

Sloppy wet with lube has been a tried and true recipe for getting these big mamas broken in, sounds like your experience is directly in line with that.

[Bjj51]

Gotcha , so it’s not uncommon for it to take more than a few hundred rounds for the break in period to be complete? Should I put the tetra lube all over the Carrier before the range r or just focus on the parts of the bcg that make contact with things?

[Matt.Cross]

Put lube on everything, bolt carrier and receiver. Remember that the lube is going to move & flow during firing, you want some of it to be moving from free areas into contact areas.

[Bjj51]

Got it , will run it swimming in lube and report back!

[98Z5V]

That vid doesn't help anything, but it shows the round getting out of your gun.  Side shot vid of the ejection port would have been better.

I just worked on a Stag 20" rifle gas barrel, over the last two weekends, for my gun pusher.  The gas port was too small.    It was a carbine stocked setup, and had recoil system problems, too, but that shouldn't be your case.  If you want to eliminate any guesswork on the recoil spring, use an Armalite EA-1095 spring or a Sprinco Red spring.  Then, you'll know for certain that the recoil spring isn't the issue. 

 

Check your gas port diameter, and come back with what it measures.  Use numbered drill bits, and use the shank of the bit to measure - not the drilling end.

Edited December 22, 2021 by 98Z5V

[blue109]

[Bjj51]

10 hours ago, 98Z5V said:

That vid doesn't help anything, but it shows the round getting out of your gun.  Side shot vid of the ejection port would have been better.

I just worked on a Stag 20" rifle gas barrel, over the last two weekends, for my gun pusher.  The gas port was too small.    It was a carbine stocked setup, and had recoil system problems, too, but that shouldn't be your case.  If you want to eliminate any guesswork on the recoil spring, use an Armalite EA-1095 spring or a Sprinco Red spring.  Then, you'll know for certain that the recoil spring isn't the issue. 

 

Check your gas port diameter, and come back with what it measures.  Use numbered drill bits, and use the shank of the bit to measure - not the drilling end.

Got it , I’ll shoot a better video next time, I found Some examples online. 

At the start of this we also measured the gas port with digital calipers and it appeared to be in spec according to some online chart. We didn’t measure with drill bits like you described (we just eyeballed it as best as possible, I wish We had done it with drill bits) so I’ll give that a try and get back to you. I dont have the tools so it May be after the holidays.

thanks for the spring recommendation 

Edited December 22, 2021 by Bjj51

[Armed Eye Doc]

What measurement did you get?

[Bjj51]

35 minutes ago, Armed Eye Doc said:

What measurement did you get?

I don’t recall the exact number but it was between .093 and .096 — if I had To guess it was .94 or .95

 

I remember that it was somewhat close but we were pretty certain it fell into that range pretty easily 

[DNP]

That sounds right from what I see tossed around here, but I’ll leave that to the gas port whisperer to confirm. Lube is definitely key. Mine wasn’t that bad, and I was feeding it pretty decent ammo, but I think I was well north of 100 rounds before I started to get consistent hold open on the last round. I know I was lighter than I needed to be on lube during that period from what I’ve learned here. 

[Bjj51]

12 minutes ago, DNP said:

That sounds right from what I see tossed around here, but I’ll leave that to the gas port whisperer to confirm. Lube is definitely key. Mine wasn’t that bad, and I was feeding it pretty decent ammo, but I think I was well north of 100 rounds before I started to get consistent hold open on the last round. I know I was lighter than I needed to be on lube during that period from what I’ve learned here. 

Gotcha , yea I’m really hoping it’s just a lube issue because I definitely wasn’t using as much lube as the other poster advised earlier. Out of curiosity, once yours was broken in do you still have to have it swimming in lube every time  or did it run consistently without as much lube later on?

[DNP]

It does fairly well with just moderate lube. I have a spray, not even sure which one. I hose the BCG off and throw it in. I’m terrible with cleaning firearms, so that comes into play on my end occasionally too. 

[98Z5V]

6 hours ago, Bjj51 said:

I don’t recall the exact number but it was between .093 and .096 — if I had To guess it was .94 or .95

 

I remember that it was somewhat close but we were pretty certain it fell into that range pretty easily 

That's on the money, for a 20" rifle gas gun with a 0.750 gas block journal diameter.  0.093"~0.096 is where you want to be on that barrel config.    Make sure your gas tube ends (in the upper receiver) right in the middle of the cam pin cutout.  That Stag I played with last week was good on gas tube length.

[Bjj51]

2 hours ago, 98Z5V said:

That's on the money, for a 20" rifle gas gun with a 0.750 gas block journal diameter.  0.093"~0.096 is where you want to be on that barrel config.    Make sure your gas tube ends (in the upper receiver) right in the middle of the cam pin cutout.  That Stag I played with last week was good on gas tube length.

Mine appears to be closer to  3/4 of the way past the cutout rather than 1/2 way. From reading your fantastic post on gas tube length this would potentially provide it with too much gas? Any thoughts?

Edited December 23, 2021 by Bjj51

[98Z5V]

9 minutes ago, Bjj51 said:

Mine appears to be closer to  3/4 of the way past the cutout rather than 1/2 way. From reading your fantastic post on gas tube length this would potentially provide it with too much gas? Any thoughts?

Nope, that's good.  Just a tick over halfway means that the barrel was drilled in between the Armalite and DPMS specs for gas port location - but they used the Armalite AR-10 gas tube to make this up.  WAY MO' BETTAH than them using a DPMS LR-308 or AR15 gas tube - and coming up short...  

Run it, don't worry about it.  It's good.  

[Bjj51]

Awesome, thanks! Sorry My reading comprehension declines greatly as the Night progresses (I work from home and my 9 month old’s day care is closed for 2 weeks due to the holidays). I now read more closely the part where you explained that going long is fine , it’s short that’s no bueno 

[98Z5V]

It's good, man - run that thing!  

[mtrmn]

I'm very late to this party, but I got something to say anyway. When you lube that BCG it needs lube INSIDE where the gas rings are as well. I've found that a few drops in the exhaust ports on the side of the carrier every 10-20 rds or so works wonders during breakin.

[Bjj51]

I disassembled and cleaned the bolt today and noticed the gas rings seemed a bit loose. Is this normal or is something out of spec? I hope the picture is clear enough but I can Push them quite a bit out with the tip of my finger 

Edited December 27, 2021 by Bjj51

[shooterrex]

That's normal. They seal against the inside of the bolt carrier.

[Bjj51]

Thanks 👍

[Bjj51]

Late update :

 

Looks like it was a cheap ammo/ needs more lube (I’ve been slathering on tetra gun lube before every range trip) / more break in issue. It now cycles perfectly with my buddy’s reloads and any factory ammo that isn’t terrible. It doesn’t like the ruag white box but even then I’ll maybe have 1-2 fte’s per 50 rounds (similar results to barnaul steel case 308). It’ll lock back on the last round with the ruag but not with the Barnaul which points to the gun not liking underpowered loads. I also Changed out the spring to a springco red for peace of mind but I doubt That was the issue. I’m sure I could Get it shooting crap ammo better by Drilling the gas port and getting an agb but that seems totally unnecessary.

thanks a bunch for all the advice, I’ve been having so much fun with this thing it’s ridiculous (forgive the commiefornia fin grips/ featureless nonsense):