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Build complete - Happy ending!
First of all I want to thank Quarterbore for a great forum. Secondly, I want to thank everyone on this board for the valuable information that I have received. In return I would like to share the details on the build I have just completed using the 300 whisper cartridge on an AR platform. I hope this report will be helpful for any of you currently building or plan on building a rifle of this kind.
Since I already had a Gemtech TPR-S suppresor for a Rem 700 308cal. with bi-lock adapter, I wanted something subsonic to shoot it on. The 300 whisper seemed to be the perfect cartridge. Since I already have a RDIS for the AR and have many years experience with the AR platform, it was not long before I yearned for subsonic supressed full auto fire. I can say now, that I have a very quiet and 100% reliable weapon.
I started with a Model 1 Sales 16" barrel w/barrel extension, milled gas block and 1/8 twist. I coupled it to a bushie flat top receiver, and bushie free float forearm. I used a standard Colt full auto bolt, that I already had lying around, and installed an extra power Wolff extractor spring (which I do on all my ARs). I will note here that I at first had the not so uncommon feeding problems, but was able to remedy this fairly easily. It seems that the M1S barrel came with a standard .223 barrel extension. Trying to feed 30 cal bullets using 22 cal feed ramps was causing obvious problems. I took the trusty Dremel and a suitable grinding stone and reformed the feed ramps to better accept the 30 cal bullet. Feeding problems solved. Also be sure to use self leveling mag followers to keep the cartridges from tilting at the rear and allowing the bolt carriers to ride up over the next to feed round in the mag. The barrel already had a .125 dia gas port so nothing was done to this. I had Gemtech thread the barrel and install a bi-lock adapter.
I at first installed a Fulton Armory adjustable gas tube, but I was not impressed with it and ended up using a standard carbine length gas tube.
As far as the lower receiver goes I switch between a bushie with a JP Enterprise match trigger (sweet) for more accurate shooting and a bushie lower with all the full auto parts for good ole full auto mag dumping.
(To be continued......)
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Threaded Mode
