Weight inside AR Recoil Buffer?

[rzym20]

When cleaning my Rock River M4 I noticed that there appears to be a weight of some sort inside the recoil buffer I removed from the stock. When I shake the buffer end to end, this weight clearly "thunks" back and forth. Seem like this shifting mass will only add to felt recoil impulse and slow down second shots.
1) Is this weight inside the buffer normal?
2) Is it normal that this weight shifts inside the buffer?
3) Is the shifting weight somehow essential for reliable weapon function?

Thanks!

[MrNiceGuy]

1) yes

2) yes, it's common. it's an easy fix with some silicon

3) no

[rzym20]

Thanks very much for the reply!

[HiBC]

Hold off on the silicon!
Its like that because it is supposed to be.
The M-4 discovered a problem called bolt bounce and that little shuffle is part of dampening it,as I understand.
See the book "Black Rifle 2"They talk about buffers.Likely yours is marked with an "H" or maybe even "H2"
If it works,don't fix it :-)

[TheManHimself]

The weight is supposed to shift. It serves to dampen bolt bounce and slow BCG reciprocation. Filling it with silicone will eliminate that function, and increase wear and stress on the bolt group - in other words, a bad idea.

If you don't have a complete understanding of the AR15 action design and how it's intended to function, please don't be recommending "fixes" to working-as-intended parts to newbies.

[MrNiceGuy]

The weight is supposed to shift. It serves to dampen bolt bounce and slow BCG reciprocation. Filling it with silicone will eliminate that function, and increase wear and stress on the bolt group - in other words, a bad idea.

you're right, it was designed to fix the problem that sometimes arose during full auto firing.

in semi auto, it's nothing but a noise maker


they also make solid buffers that reduce carrier bounce in full auto
http://www.rangeroutreachcenter.com/Rifle%20Model.html

to save money and quiet down your semi auto, the silicon works great
i strongly recommend it