Model 1 Sales 300 whisper upper function problems

[jripper]

I agree that moving the gas port to the pistol position would be the best way to go. I do not have a problem with my AA 1680 load with subsonics, with either a full butt stock, or car, using stock springs and bolt carrier. However, as previously noted, it will not work with faster powders. This is adequate for my uses. However, if you want it to function with any subsonic loads, you had probably better move the port.

Joel

[MMA10mm]

Well, before modification, Cor-Bon 220gr Subsonics won't work, but my handloads with 150gr FMJs and 17.5grs of W-680 (Surplus from Jeff Bartlett) worked just fine... Cycled every time!

Also was able to make hot loads with H-110 work, but they were about 1.0gr overload. (They were right at the suggested max load from SSK, and I was using more voluminous Rem. 221 brass vs. the re-formed mil. brass that SSK uses, but they were still hot...)

Anyway, at least I could get the thing to shoot semi-automatically before modification... I'll probably shoot it some more and then do the mods when the weather gets bad.

[TerroristHunter]

Just put together my M1S barrel on a CMMG upper with an Adams Arms Piston kit. Haven't tried the AA1680, but H110 and Reloader 7 haven't cycled yet. After drilling out my barrel to the same size as the gas block hole (.155) it will at least eject. I have also cut 1/4 off of the buffer spring (and stretched it out), and removed one of the weights from my buffer. The Adams Arms is a heavy Bolt carrier, but there is an option of just installing a key on a regular carrier. (Maybe chrome lightweight) Will keep you posted...

[TerroristHunter]

By the way, M1S will turn the barrel down to install a pistol position gas block, but it costs an extra $100.00

[mak91]

I got a m1s 300 whisper barrel back in 2004. Did the same thing, drilled out the port, cut the buffer spring, tried a bunch of different loads with Reloader7, Accurate 9, and Hodgdon335. Got some loads to cycle most of the time but never got 100% reliability. I also wanted to shoot some non subsonic loads some time and this setup would not work for the higher pressures. I finally figured out something to try, a double gas port configuration. I had tp555 make me a custom gas block. The adjustable gas block has 3 settings, off, pistol gas port and carbine gas port. In pistol gas port position the carbine port is blocked and gas only flows back to the bolt from the pistol port, same goes for the carbine port position, gas only flows from the carbine port to the bolt, the pistol port is blocked. This gives me the best of both worlds. Since I had already drilled out the carbine port to a larger size trying to get it to work in the original configuration I now have to use an adjustable gas tube to get the pressure right.

[Artful]

Pretty trick - what did that set you back?

[mak91]

I did all the work my self except for the gas block. For the block I had tp555 make me a prototype off the block he was already making. I am not sure what he would charge to do this work or for the block. IM or email him, real nice guy to work with......