wont lock back on empty mag. old story, weird twist

[xxlfitness@yahoo.com]

Guys I know we have all seen these posts before and we know all the common reasons for this.

This one however is a little weird.

I shot a new 308 that I just completed for the first time this weekend. It was a quick function only test since it was 0 degrees outside and  I was not dressed for extended fun outdoors. The rifle ran well with 10 rounds through the 10-round magpul P-Mag but when the mag was empty, no lock back. I ran a second 10 rounds, same smooth function but no lock-back.  I was surprised because it all works well and bolt locks back as it should when I manually pull back the bolt with the charging handle, each and every time locks in solid. All the parts seem to mesh well and engage solidly. So I started thinking, maybe short cycling?,  the bolt not coming all the way back due to too much spring or too heavy a buffer? But if that were the case, why would the gun run so nice and even perform a  quick triple tap without a hiccup? feed well, extracted well, etc.

I was using a basic ammo that I picked up quick at rural king, some soft nose, 150 grain American Whitetail Hornady stuff. I normally do not ever run this type of Ammo through any of my AR's as I mostly run FMJ ammo. I did notice some very shallow dents in the brass in the same spots on about half the rounds but I hear that is not unusual in the 308. ALL of my experience with AR's to this point is .556 stuff.

Now here is one other weird aspect to it. if I pull back the bolt with the charging handle and lock it back, then insert a magazine, and then hit the bolt release button, the top round does NOT peel off and feed into the chamber, it gets hung up each time. BUT, if I pull back on  the charging handle and pull the bolt back just slightly further than where it would normally catch with the bolt catch, and let the bolt fly, it will feed. Its almost like the lock back point is not quite far enough back to fully clear the round and pulling back on it just a few thousands more, lets it get behind the round if that makes any sense.

In the past with AR-15's, I I have been able to load a mag, hit the bolt release and have it reliably chamber a round fully into battery. but not with this 308.

Are these two issues related?

Your thoughts?

[Sisco]

Xxl, first thought; try a different magazine. It sounds as if there is a small difference in the magazine position from where it should be to lock back, and to strip a new round out of the mag when it is locked back. Need to rule out a possibly defective magazine. Also possibly it could be a tolerance issue between the upper and lower. Any visible gaps between them? Also, switch ammo to make sure it is not a specific issue with that load. With that I will sit back and let the really knowledgeable guys weigh in.

[edgecrusher]

First what is your buffer system (spring, buffer, tube). Secondly, soft nose ammo is known to not feed well into AR type rifles, it will hang on the feed ramps or damage the nose of the round.

[survivalshop]

   

 How about some info on this new rifle or build ?

Could be light powered ammo , but has enough to strip the next round .

   Is the Bolt catch catching on the Bolt Face , when you lack the BCG back ?

   As above , Soft tip exposed lead Bullets do not feed well in a lot of AR type rifle , some do , some don't , like them .

    And yes , the Buffer Spring can be wrong or too much spring tension .  

[xxlfitness@yahoo.com]

Yes, I am hoping your right about that, maybe  somehow that soft nose contributed to the problem, I have never run that kind of ammo before as I said, just seems wrong in an AR platform LOL

Sisco, good points with trying a different mag and of course the ammo we all agree on.

Upper and lower seem to fit nicely together, its a Aero lower with a generic DPMS style upper from Cobratac.

 

edge Crusher, as to the buffer system, I need to get some more skinny on that.

I know its the longer buffer tube of course, with the longer and heavier buffer, weight I will have to double check, and the spring is a stainless spring, but not a flat wire spring just traditional but stain less spring.

One things guys I was  wanting to get some consensus on, do we all agree that locked back by the bolt catch, the top round should strip off when released and feed fully into battery without having to pull back further on the charging handle to gain more momentum?

 

 

[xxlfitness@yahoo.com]

Survival shop,

The set up is a 24" stainless fluted barrel, 

Aero lower, with a generic DPMS style upper from Cobratac.

Luth stock. The spring, buffer and tube I need to get some more data on to be accurate, sorry, mike

Edited January 3, 2018 by xxlfitness@yahoo.com
msp

[xxlfitness@yahoo.com]

I found some of the data working on more.

here are the specs on the buffer itself:

308 5.5 oz weight
Features:
Fit: LR-308
Length: 5.285"
Weight: 5.5 oz

[98Z5V]

Take pics of the right side of the lower receiver, clearly showing the mag catch button.

You had an issue with a .308 mag catch not too long ago.  If not properly installed, that can certainly cause the exact problem you're describing.

[xxlfitness@yahoo.com]

The mag locks in just as it should by hand, I even have the extended release button called for by Aero in their lowers. The normal threaded stud is a bit too short on most of the mag release hardware and I had to get a longer one. I can take a pic though no problem

[xxlfitness@yahoo.com]

new information and some of my buffer stats were off.

 

Buffer tube length ID 9 3/4"

Buffer spring Stainless relaxed length 12 1/2" long, x 29-30 coils

Buffer length with nose 6"

Buffer length without nose 5 9/16"

Buffer weight will be available tomorrow when I can weight it exactly

[98Z5V]

15 hours ago, xxlfitness@yahoo.com said:

The normal threaded stud is a bit too short on most of the mag release hardware and I had to get a longer one. I can take a pic though no problem

This is part of my point here - the AR-15 mag release isn't too short.  It doesn't need to be longer, to fully install and function fine.  I have 4 of these things as living proof.

You stated your buffer was 6" long.  Something's wrong with the buffer, for absolute certain.  AR-15 rifle buffers are 5.900" long, and .308AR rifle buffers are 5.200" long (if they're not RRA LAR-series).  

 

[xxlfitness@yahoo.com]

Well to make maters even more interesting, I just weighed by buffer on a professional scale and it weighs in at 6.2 oz. What odd is that when I bought it, it was advertised as weighing 5.5oz

[xxlfitness@yahoo.com]

Ok,. I'm hoping this post clears up a lot of questions for you and for me.

ISSUE #1 My buffer upon remeasuring it is 5.91" long. It weighs exactly 6.2 oz.

This buffer was advertised as being for a ,308 and was also advertised as being 5.5 oz which obviously it is not.

The buffer tube is exactly 9.75" inside dimension.

The buffer spring is a stainless spring, 12.5" long relaxed, with  29-30 coils. If it would help to measure the wire size, I'd be happy to do that.

 

ISSUE #2 Magazine catch/release button assembly.

98Z5V DEWS. I'm not trying to be adversarial and I very much appreciate your help but... There is a known issue with Aero lower receivers in the 308 and  possibly the AR-15 5.56 as well although I have no experience with that. A normal size stud will NOT be long enough to engage properly with sufficient thread engagement a normal size release button. This can be resolved one of two ways, the Aero lower parts kit includes a longer than normal button which seats deeper into the receiver to work with the standard size button release stud. OR  another way to solve it is to use a standard size button release with a LONGER stud sold by KAK as an example which ALSO works.

This information has been verified by speaking with the tech support folks at Aero and you can verify this yourself by calling or emailing  them. I do agree though, this is a little know issue by many people and it took me a while to understand what was going on and ultimately a phone call to them,

Please continue to help with the buffer issue though, I do appreciate it.

mike

 

[98Z5V]

6 hours ago, xxlfitness@yahoo.com said:

Ok,. I'm hoping this post clears up a lot of questions for you and for me.

ISSUE #1 My buffer upon remeasuring it is 5.91" long. It weighs exactly 6.2 oz.

 

ISSUE #2 Magazine catch/release button assembly.

98Z5V DEWS. I'm not trying to be adversarial and I very much appreciate your help but... There is a known issue with Aero lower receivers in the 308 and  possibly the AR-15 5.56 as well although I have no experience with that. A normal size stud will NOT be long enough to engage properly with sufficient thread engagement a normal size release button. This can be resolved one of two ways, the Aero lower parts kit includes a longer than normal button which seats deeper into the receiver to work with the standard size button release stud. OR  another way to solve it is to use a standard size button release with a LONGER stud sold by KAK as an example which ALSO works.

This information has been verified by speaking with the tech support folks at Aero and you can verify this yourself by calling or emailing  them. I do agree though, this is a little know issue by many people and it took me a while to understand what was going on and ultimately a phone call to them,

Please continue to help with the buffer issue though, I do appreciate it.

mike

 

ISSUE #1 is taht you have an AR-15 rifle buffer in there.

ISSUE #2 is just pure bullpoopy.  3 of the big ARs I have are Aero M5 sets.  Not one single one of them is running any special mag release, at all.  They're all running regular run-of-the-mill AR-15 mag releases, and buttons.  All of them.

You are mistakenly thinking that you need to bury that mag release button on the threaded stud until it's flush - and you don't. There's PLENTY of engagement on a standard release, and a standard, non-fancy button. 

What you're not understanding here is this - for many, many years, the large-frame ARs have been around.  For all those years, there was never a special mag release assembly for these large ARs, and everything worked fine - for all those years.  Now, companies are cropping up everywhere, customers are asking questions, and companies are either making new parts to satisfy customers that don't know the difference - or the companies don't know the difference.

Now, as far as Aero goes - I don't care who you spoke to, what they told you, etc.  That doesn't make what they told you accurate, or unarguable.  How many of those guys built a large frame AR 10 years ago?  What mag release setup did they use then?...

I'm telling you, plain and simple, that my Aero M5 lower receivers all have regular AR-15 mag releases and buttons in them, and they all function just fine. 

Now, please explain to me how you can't install a regular AR-15 mag release asembly in an Aero M5 lower receiver.  Please, explain to me that it doesn't fit, and doesn't work.-

[xxlfitness@yahoo.com]

Let's agree to disagree buddy and call that one over. I do respect your opinion though.

On the issue of the buffer. You say I have an ar15 rifle buffer in there? Please help.me understand your point and what you think it SHOULD have and please be specific.

Keep in mind, the buffer is 6.2 oz. Have you seen an ar15 rifle buffer that heavy before?

Mike

[98Z5V]

Where did you buy it?  The buffer, in your Big AR, where did it come from, and what brand is it?

[Matt.Cross]

1 minute ago, 98Z5V said:

Where did you buy it?  The buffer, in your Big AR, where did it come from, and what brand is it?

I'm kinda hoping it's one of those $3.46 Amazon specials made with pride and child labor in Thailand.

[survivalshop]

Double post 

Edited January 4, 2018 by survivalshop

[survivalshop]

On 1/2/2018 at 9:24 PM, xxlfitness@yahoo.com said:

Luth stock. The spring, buffer and tube

 

7 hours ago, 98Z5V said:

Where did you buy it?  The buffer, in your Big AR, where did it come from, and what brand is it?

 That Stock set up has had issues with other Rifles here before .

[xxlfitness@yahoo.com]

Not sure where I got the buffer. Trying to find receipts for it now and have not been able to yet.

As far as the stock, wouldn't it only matter about the tube and not what stock was on it?

 

 

[survivalshop]

17 minutes ago, xxlfitness@yahoo.com said:

Not sure where I got the buffer. Trying to find receipts for it now and have not been able to yet.

As far as the stock, wouldn't it only matter about the tube and not what stock was on it?

 

 

 I was under the impression you punched it as a Kit .  Purchasing separate, thats even more of a red flag , as to the possibility of wrong mix of components .

[survivalshop]

1 hour ago, xxlfitness@yahoo.com said:

Not sure where I got the buffer. Trying to find receipts for it now and have not been able to yet.

As far as the stock, wouldn't it only matter about the tube and not what stock was on it?

 

 

 Was it a Kit like this ?

https://www.brownells.com/rifle-parts/receiver-parts/buffer-tube-parts/buffer-tubes/ar-308-rifle-buffer-tube-assembly-prod110083.aspx?lp_pageid=add2&crtitemid=Home_New_Products&rrec=true

[Sisco]

2 hours ago, survivalshop said:

 

 That Stock set up has had issues with other Rifles here before .

First I have heard of this. I transitioned to a Luth stock with the standard Armalite AR10 buffer with no problem. I would change the buffer/spring first. Before messing with the stock.

[survivalshop]

8 hours ago, Sisco said:

First I have heard of this. I transitioned to a Luth stock with the standard Armalite AR10 buffer with no problem. I would change the buffer/spring first. Before messing with the stock.

 I meant the stock assembly when I referred to the Stock , not the Stock itself .  Its what I said in my last post , the Kit form , with Buffer, Spring & Receiver Extension . Is that clear enough for everyone now 

Edited January 5, 2018 by survivalshop

[Sisco]

30 minutes ago, survivalshop said:

 I meant the stock assembly when I referred to the Stock , not the Stock itself .  Its what I said in my last post , the Kit form , with Buffer, Spring & Receiver Extension . Is that clear enough for everyone now 

Aah! I saw that kit but had no need of it. Xxl hasn't really told us if the whole stock and buffer/spring came from Luth.