New Whisper SBR Build

[too_many_hobbies]

Please expand on the purpose of the on/off gas block. I assume that it stops the AR from cycling and therefore reduces the noise when fired. If I am correct, is the noise reduction significant?

If the gas block is located under the forearm, how do you access the on/off switch?

Would there be any point of impact change when switching the gas block on and off?

Please provide me with contact information for tp555.

I have a 10.5" Shilen coming and would like to incorporate this feature if possible. I am using a YHM Four Rail Free Float Forearm (I think 9631). Any idea if the on/off gas block would have to be modified to fit under this forearm?

[Scoop]

Originally Posted by too_many_hobbies

Please expand on the purpose of the on/off gas block. I assume that it stops the AR from cycling and therefore reduces the noise when fired. If I am correct, is the noise reduction significant?

If the gas block is located under the forearm, how do you access the on/off switch?

Would there be any point of impact change when switching the gas block on and off?

Please provide me with contact information for tp555.

I have a 10.5" Shilen coming and would like to incorporate this feature if possible. I am using a YHM Four Rail Free Float Forearm (I think 9631). Any idea if the on/off gas block would have to be modified to fit under this forearm?

Did a little work at the range this morning. The rifle functions perfectly in semi-auto mode and manual bolt mode. The little gas block worked well and the push button is easy to manipulate through the slot in the handguard. Accuracy was the same in both modes (just over half moa). Point of impact with the rifle zeroed in manual bolt mode was less than half an inch lower in semi-auto mode. Velocity difference was negligible. At 1044 fps avg in Bolt mode and 1028 fps avg in semi-auto mode it yielded a whopping 16 fps avg difference. Noise levels were less in bolt mode, but not as much difference as I had expected. Shot noise seemed the same, but of course you had the added action noise in semi mode. I doubt you could tell the difference 50 yards from the shooter though.

This block will easily fit under your YHM FF Rail. It will fit under any 2.0 inch ID rail. The VTAC is 1.75 inches ID and I had to do a little grinding to get it to fit.

tp555 is a member on this board so you can contact him via PM here.

[Scoop]

More good info and pictures of other options HERE and HERE.

[Flintstone]

Just got my gas block from tp555 and the upper/ bolt carrier from fulton...What a great father's day. I wanted to thank you for putting out this great info.

Also, looking at tp555's work, he appears to be a hell of a machinist/engineer. I wish I had talent like that.

[Scoop]

Flintstone - Hope you enjoy yours as much as I'm enjoying mine. Fun little gun to shoot.

[hugginsvilleH&A]

where /who has these "tp555's on/off gas block" ???

[Gpz1100]

http://www.quarterbore.net/forums/showthread.php?t=1478

[steezo757]

Scoop,

I'm pretty sure we have the same barrels...Your Noveske barrel is 0.875" in diameter at the gas block, right? Did you have to mod the gas block any to allow it to fit underneath the handguards? I just re-read your post. How much did you have to take off? Do you happen to know, what the inner diameter of the JP handguards are? I looked it up on the JP website, the I.D. is 1.75".

I'm trying to exhaust all options before I send my Noveske barrel off to be re-profiled.

[Fudmottin]

I have tp555's on-off on my 223 and three way on my 300-221 uppers.

The on-off block is awesome. You don't realize just how loud the action is until you completely banish that noise. Felt recoil also seems to go down, but video shows the same exact amount of recoil.

My on-off got shaved down a tiny bit to fit in the standard position on the 223. The 300-221 just barely fit under a 1.75" ID hand guard. Things to keep in mind. My 223 has a 1" barrel to the block and then 0.930 the rest of the way. The 300-221 is 1" to the block (in the pistol position) and then 0.750" the rest of the way. I have a standard length hand guard on both.

If you want the block under the hand guard, you probably need either to go with only a 0.750" barrel or find a larger than 1.750" ID hand guard.