What is this part on gmr-15?

[egd5]

At the bottom of the buffer tube there is a thin washer (for lack of a better name) with a slot in it. The slot appears to line up with the bottom of the scs system. It is not attached to anything and it looks like maybe grease is what holds it onto the scs.

What is this for and is it supposed to be attached to something? Thanks

[msp1jpp]

It is a spacer. If required it pushes the scs towards the bolt. The scs should not have any free movement between the rear of the bolt.  Shake test it.

[Darqusoull13]

On 8/6/2019 at 5:59 AM, msp1jpp said:

It is a spacer. If required it pushes the scs towards the bolt. The scs should not have any free movement between the rear of the bolt.  Shake test it.

Exactly this. The SCS should protrude the buffer tube roughly 0.03", or the width of the shim. It may not be necessary. 

[egd5]

Does it matter if the slot lines up with the scs assembly?

[msp1jpp]

No

Edited August 8, 2019 by msp1jpp

[msp1jpp]

[egd5]

Thanks.