What is the purpose of the 2 piece buffers on TASK and Sabre uppers?

[sausagemc]

I keep seeing offers that have the center drilled out and a second spring and plunger installed, what is the purpose of that? My saber upper has the same thing but I don't know what the true purpose is almost like it is a heavier spring that if the buffer bottoms out it prevents it from hitting hard? Almost a progressive type of spring setup... why not just use a heavier buffer if that is the case?

 

[gotgraham]

The special buffer gives you about 1" more of recoil distance with a standard buffer tube, increasing reliability of catching the sear properly. It may serve an additional purpose, but that was the specific challenge I ran into when building my sabre clone. Since i didn't have the special buffer, I used a VLTOR A5 tube, which is about 1" longer - coupled with an standard carbine buffer.

 

[sausagemc]

Hence the question about using a heavier buffer? Wouldn't slowing it down be the desire or is it locked all the way back and spring right with the upper.

 

[gotgraham]

The issue is actually that there isn't enough recoil space to engage the second sear catch on the bolt. If you have a sabre, try it. Put a normal carbine buffer in and you'll see you can only get it to the first catch - which won't allow you to strip another round out of the magazine. You need the additional 1" or so of space to get to the second sear catch - which will allow you to strip another round out of the mag.

You can shorten the recoil rod as short as you can safely shorten it - and you can then catch the 2nd sear on the bolt - but not reliably. It ends up with all of 1/8" recoil space behind the sear. Heavy buffer or not - it's not enough to be safe. So the extra recoil space resolves the issue.

 

[mak91]

It also pre loads the bcg with a little bit more spring pressure where you need it the most when the bolt carrier is almost completely forward and its time to pierce the primer.

 

[sausagemc]

Thanks, now I understand the system!