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#7166985 - 05/11/18 11:27 AM Need Help w/300 Blackout Subsonic Not Cycling
Stripermania Offline
Light Foot

Registered: 04/13/11
Posts: 42
Loc: DFW
I bought a cheap DPMS AR-15 Sportical from Academy and removed the upper and installed a "Complete Radical Firearms 16" 300 BLK 1:8 Pistal Length HBAR 15" M-Lock FCR Rail" and an 8" YHM Phanton 7.62 suppressor and 10 round P-mag magazine from Academy. Also, it has the Slide Fire Bump stock but I have the bump stock in the locked position so it acts as the regular stock (non-automatic). I shoot 110g supersonic Hornady V-Max and it shoots and cycles good but when I shot 185 Grain Subsonic, it doesn't cycles. I don't know much about AR so can someone tell me what I need to do to shoot subsonics so that it will cycles. The Shell does eject out but the next round sometimes stove pipe or doesn't even leave the magazine. Thanks,

Edited by Stripermania (05/11/18 11:37 AM)

#7167022 - 05/11/18 11:56 AM Re: Need Help w/300 Blackout Subsonic Not Cycling [Re: Stripermania]
ChadTRG42 Offline
THF Celebrity

Registered: 09/16/09
Posts: 13737
Loc: Lewisville, TX
There could be several things going on. First, is your gas block adjustable? If so, open it up all the way to help aid in cycling the subs. The gas block needs to be open all the way to allow as much gas as possible to cycle the action. A piston gas system is easier to cycle subs than direct, so it should work. Also, I would check to make sure your gas block is lined up properly, since you added a new hand rail.

Next, 185 grain subsonic ammo will be harder to cycle than a much heavier bullet, like a 208 or 220 grain sub. The dwell time on the 185 grain is less, therefore having less time for max pressure to cycle. The suppressor needs to be on the rifle when shooting the subs. The suppressor adds more back pressure to the round and helps aid in cycling.

Who's ammo is it? I don't know of a 185 grain sub load. If the ammo is loaded really slow (900-950 fps), there is less powder inside the case, which means less pressure to cycle. Some factory ammo is loaded slow, even for a subsonic load. I have spent A LOT of time and research on my subsonic 300 blk out ammo to get it to work just right in a given barrel length.

Custom and Precision Ammunition!!
Type 01 and Type 06 FFL

#7168442 - 05/13/18 08:19 AM Re: Need Help w/300 Blackout Subsonic Not Cycling [Re: Stripermania]
Couzin Offline
Pro Tracker

Registered: 12/31/07
Posts: 1124
Loc: Terrell, Texas
Yep - adjustable gas block! If the bolt is not movimg enough to strip off the next round you need more gas so yes, open it up. For a little extra fine tuning, get a captured spring buffer with different rate springs. It will save a lot of wear and tear.
“Only at the end do you realize the power of the Dark Side.”

#7168666 - 05/13/18 03:53 PM Re: Need Help w/300 Blackout Subsonic Not Cycling [Re: Stripermania]
roughneck266 Offline

Registered: 08/10/08
Posts: 96
If what was suggested above doesn't do anything for you, check the gas port size. I have seen several Radicals with smaller holes for the 300. It can be drilled out to .125".


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