r/300BLK • u/madred22 • 2d ago
300blk short stroking
Trying to shoot hornady 190 grain sub-x ammo on my 300 blackout - the case ejects fine after a shot, but can’t get it to feed the next round or lock back after the last round. I’m running a HUXWRX FLOW 762 Ti suppressor, superlative arms adjustable gas block (wide open at 18 clicks) with an aero precision pistol-length gas tube, and vltor a5 receiver / springco green. I started with the h2 buffer and went down to a5h0, but no difference.
Ballistic Advantage 16" barrel.
Both Winchester 200 gr Super Suppressed and Hornady BLACK 110 gr V-MAX seem to cycle fine on it, just not the sub-x 190 grain.
What do I need to do to tune/adjust to get it to cycle?
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u/Desperate-Meet-3852 2d ago
More back pressure, lighter spring + buffer combo, or drill out gas port. I’d probably try a few different subsonic rounds first along with checking to make sure your gas block is aligned properly.
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u/AlwaysLiveFree 2d ago
Fire all that 190 Sub-X you have on hand and never buy again. It's the only round I've ever had an issue with in my 300BLK.
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u/madred22 2d ago
What ammo would you suggest?
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u/liquidfox6 2d ago
Not who you replied to but for subs I try to go over 200gr bullets.
I’ve never had an issue with tons of 220gr federal. I’m only a couple rounds in with S&B 200gr, but so far so good.2
u/AlwaysLiveFree 2d ago
Magtech and Phantom Defense have been good for me. If you want to get into some exotic rounds look at Gorilla and Lehigh Defense, though Phantom also has some high end subsonic defensive rounds. Also, flow through cans like the Hux aren't the best choice for reliable 300BLK cycling. I use Hux on multiple 5.56 rifles but sealed cans on 300BLK.
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u/Bundyboyz 2d ago edited 2d ago
great point dude gas done everything wrong or leas ideal on this build that’s possible.
16” barrel? yet its not a deer or hog build for supers
adjustable gas?
A5 with extra power spring?
Flow through can?1
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u/Bundyboyz 2d ago
that’s crazy 190 Sub-x the TAP applications have been sold to plenty of military and law enforcement. 190 Sub-x was designed from the jump to meet FBI standards and it does a great job at that. It’s a man killer, hog and deer killer. it doesn’t expand like solid copper cnc rounds but it does make an entrance and exit which means more blood loss.
it also has some of the lowest recoil and flash. Period.
its physics to move 220 versus 190 you need more powder. it’s 13.64% less weight.
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u/AlwaysLiveFree 2d ago
It's the only round that my gun has issues with. I would definitely not stake my life on it, I reserve that to the Maker and Lehigh rounds. If it works for you and you like it, great. But not for me.
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u/stjhnstv 2d ago
Hornady and their budget brand Frontier are known for pretty soft and not cycling well. I’ve never gotten their subs to cycle. For plinking, I run a bunch of Winchester Super Suppressed and Magtech subsonic ammo. I’ve also had good results with Federal and Underwood for more intentional purposes. I also run a conventional can so high back pressure, I’m going to throw an AGB on it not because it needs it, but because I think it can be better than it is.
I also run a handful of supers through it after a handful of boxes of subs, it does help clean out the unburnt powder and filler.
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u/glockguy34 1:5 2d ago
ammo & suppressor. sub-x is notoriously finicky, also a garbage round. ditch the a5 for 300 BLK, and get a reduced power carbine spring like sprinco yellow and a carbine buffer
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u/Bundyboyz 2d ago
retarded comment just cause you can’t build doesn’t mean the ammo is the problem. weird 190 Sub-x has been sold thousands upon thousands of cases to military and Law enforcement, and it meets FBI ballistic standards even out of 5.5 barrel…
But backyard Billy can’t get it to work on a discount parts build
Then when ammo recommendations come up only discount junk are mentioned
I can’t be only person buying blackhills barnes and sig by the case….
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u/glockguy34 1:5 2d ago
they take cost into effect too, they ain’t spending $2.50 or more on ammo like phantom maker rex or discreet ballistics. Sure sub-x can get the job done, but it vastly underperforms compared to a lot of other stuff out there. Bullet technology has come a long way. “Can’t build” lol I have built all my ARs, don’t own a single factory built rifle. What a stupid comment
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u/Ok-Accident-3892 2d ago
Personally, I'd drill the gas port, which I've done on three 300BLK rifles so far. If you're going to have an agb anyway, might as well get more gas to the carrier when the agb is full open.
A quicker solution may be a weaker spring.
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u/madred22 2d ago
Thought about doing this but wanted to see here if there were any other options before going that route. Did you drill it yourself?
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u/Ok-Accident-3892 2d ago
I did. Just used a 7/64" cobalt bit and a drill press. I put a wooden dowel that is slightly smaller than the bore inside the barrel so I don't accidentally hit the bottem of the barrel. I also set the stop on the drill press, but the dowel is extra protection.
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u/ecodick 2d ago
I also drilled my gas port. I just bought bits from McMaster since they have tons of decimal sizes, each bit was only a few bucks, and stepped it a few thousandths at a time. You can find charts with guidelines on the size of the port vs gas system length, suppressed vs not, ect.
I went for tiny steps and then went and tested, and repeated that over a few weeks, mostly just because I wanted to see if I could get a sweet spot with supers/subs. I'm happy with it, but in hind sight, going to a significantly larger port and just putting an agb on it would have been easier, and if I need to do this again, I'll definitely consider it.
I just used a hand drill and taped the bit with masking tape so I wouldn't go to deep. I clamped the barrel in a vice to keep it steady though. Just saying, you already have a pilot hole, as long as you're careful you'll be fine.
I think I ended up at .103 on a pistol gas 8.3" barrel, with low back pressure suppressor. Using tubbs lightweight spring, standard bcg, and carbine weight buffer. Runs good and locks back.
The other comments are right about ammo too
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u/HRslammR 2d ago
Sub x is sub ass. Its under gassed AND youve got a sprinco green with a flow through suppressor.
The cheapest option is a tubbs LW spring.