Buffer kit or BCG malfunction

[Ivan]

Good morning, Group.

I am new here and into putting together rifles. Built successfully several AR15s,, but I hit the rock with this .308 rifle.

It supposed to be a beautiful high end built and it is expensive, but it comes with a problem.

I used a carbine AR15 buffer kit I had already in my parts boxes and it doesn't function right. 

The rifle was never shot. When charging the BCG gets stuck in the tube. When I pull half way, just enough to load it comes back the way it supposed to do.

Lower is CMMG MK-3 with CMMG internals. Only the trigger is a Geissele (which I have no idea how to adjust, but this is for later)

Upper came assembled by Falkor Defense with their receiver and handguard. Barrel is Proof carbon wrapped, rifle length .875

BCG is DLC made by Sharps Rifle Co. out of WY

Attached are picture for reference

Please, Guys,  HELP

If You think it is the buffer kit, please tell me what to get. Anything good I can find in stock. 

 

Edited November 25, 2021 by Ivan
Wrong picture format before editing

[98Z5V]

What's the internal depth on that carbine receiver extension?   There are only two propper possibilities; 7.000" internal, or 7 5/8" internal.  No matter which one it is, that 3.250" long AR15 carbine buffer shouldn't allow that BCG to slam into the ears on that lower receiver.

Edited November 25, 2021 by 98Z5V

[Ivan]

5 minutes ago, 98Z5V said:

What's the internal depth on that carbine receiver extension? 

It is 6.9685 inches or 6 31/32 in fraction

[Ivan]

40 minutes ago, 98Z5V said:

What's the internal depth on that carbine receiver extension?   There are only two propper possibilities; 7.000" internal, or 7 5/8" internal.  No matter which one it is, that 3.250" long AR15 carbine buffer shouldn't allow that BCG to slam into the ears on that lower receiver.

What do You think my problem is? 

[shooterrex]

This is the recoil system that works.

https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories&Category=4eeff98b-d9a6-40fd-be6b-ab2e44ec1080

 

What is the size of the gas port in the barrel.

That looks like a low mass BCG.

Where does the gas tube end in the receiver?

[Armed Eye Doc]

2 hours ago, Ivan said:

What do You think my problem is? 

With a ~7 inch receiver extension, you need a 2.5 inch buffer that weighs 5.4  oz.  An AR15 carbine buffer is too long and too light.  As was linked above, the Armalite carbine kit will work very well.

[98Z5V]

12 hours ago, Ivan said:

There's contact on the ears of the lower receiver by the BCG in this pic above. 

12 hours ago, Ivan said:

It is 6.9685 inches or 6 31/32 in fraction

With that internal depth measurement, and a 3.250" long AR15 buffer, it's not even possible for the BCG to make contact with the lower receiver in the spot that it did.  Did you cycle the gun without the buffer and spring in there, once or twice?  Something marked that lower.

At any rate, you can shiitcan the whole recoil system, and save it for an AR15 build, and get the Armalite kit that was suggested, OR...

You can get a KAK .308AR Shorty buffer that weighs 5.3oz (close enough) and use a Sprinco Orange recoil spring with it, in the extension that you've got.

Then, you need to see if you need to fix the gas tube, and the gas port size.

Then, your gun will run.  Guaranteed. 

Here's info on why this stuff works:

 

Edited November 26, 2021 by 98Z5V

[Ivan]

8 hours ago, 98Z5V said:

There's contact on the ears of the lower receiver by the BCG in this pic above. 

With that internal depth measurement, and a 3.250" long AR15 buffer, it's not even possible for the BCG to make contact with the lower receiver in the spot that it did.  Did you cycle the gun without the buffer and spring in there, once or twice?  Something marked that lower.

At any rate, you can shiitcan the whole recoil system, and save it for an AR15 build, and get the Armalite kit that was suggested, OR...

You can get a KAK .308AR Shorty buffer that weighs 5.3oz (close enough) and use a Sprinco Orange recoil spring with it, in the extension that you've got.

Then, you need to see if you need to fix the gas tube, and the gas port size.

Then, your gun will run.  Guaranteed. 

Here's info on why this stuff works:

 

I do not remember if cycled without a spring and a buffer. 

I already ordered the Armalite kit and will touch up the points of contact on the ears with black paint

I will keep keep you posted what are the results

Thank You for the reply