New Whisper SBR Build

[Scoop]

Just finished building this 300 Whisper/Fireball. She shoots like a dream. The first 4 rounds (220 gr SMK Subsonics) down the tube went into .875 inches at 100 yards. Things got better from there. Groups are averaging around .625 with my home-rolled subsonics. Cycling is flawless. John Noveske is the man!

Here's the specs:
Noveske 10.5 inch 1x8 Twist barrel
CMT Upper
DD 9.0 Forend
Young Manufacturing NM Bolt Carrier
CMT MP-Tested Bolt NP3-coated
PRI Gasbuster Charging Handle
GG&G 20 moa GS-1 Rail
ARMS #22L Rings
Leupy 3.5x10x40 M3 MilDot
SWR Omega Suppressor
Oly SBR lower
CMC Single Stage Match trigger
MIAD Grip
Standard M4 Buttstock
H-Buffer

[chuckp]

What powder loading are you using for your home-rolled subsonics?

Chuck

[Scoop]

Originally Posted by chuckp

What powder loading are you using for your home-rolled subsonics?

Chuck

Fairly standard Vanilla Subsonic load. 220gr SMK, Keith Davis Brass, 9.2 gr H110, 205M Primer, 2.190 C.O.L. Works great for me. Avg 1020 fps and just over half moa. Standard disclaimer - Use at your own risk.

[AlcoholicusMaximus]

awesome. I am waiting for my form 1.Have you tried any supersonic ammo in it yet? Did John advise against that?

[Scoop]

Haven't tried supersonic stuff yet. John mentioned that these barrels were set up primarily for subsonic, but he did not specifically forbid the use of supersonic fodder.

I'm thinking of making this a select-fire weapon (as in semi-auto or manual bolt action) by using one of tp555's on-off pushbutton gas blocks and a Fulton side charging upper. In that configuration, I get the best of both worlds. Just in the tire-kicking stages right now. Got a lot of measuring/figuring/thinking-it-through kind of work to do first.

[Scoop]

Finally got around to doing the bolt action AR. I wanted a selectable semi-auto/manually operated setup so that I could determine when to make the extra noise. Using tp555's on/off gas block let's me go back and forth between semi-auto and manual bolt action. Just got it all put together. Had to modify that gas block a bit to make it fit under the handguard. Gonna put rounds downrange tomorrow. Here's how it all shook out.

Final specs:
Noveske 10.5 inch 1x8 Twist barrel
Fulton Armory Side Charging Upper
JP VTAC FF Tube
tp555's on/off pushbutton gas block
Harris BR Bipod
Fulton Side Charging Bolt Carrier
CMT MP-Tested Bolt
Standard Charging Handle just to fill the hole
GG&G 20 moa GS-1 Rail
ARMS #22L Rings
Leupy MK4 2.5x8x36 M2 TMR Reticle
SWR Omega Suppressor
Oly SBR lower
CMC Single Stage Match trigger
MIAD Grip
Vltor A1-length Rifle Stock
Standard Rifle Buffer

[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.