PSA 10.5" upper and lower.
Magpul gen 3 300blk 30rd mag.
Torx 35rd 5.56 mag
Magpul gen 3 30rd 5.56 mag
Mil-spec metal 30rd 5.56 mag
Drilled gas port
Standard gas block/tube
Psa custom drop in trigger.
Sprinco yellow buffer spring
Mil-spec buffer spring available
1.7oz - H1 buffer available
Q trash panda w/cherrybomb muzzle device
The issue im having is that when shooting 220gr subs everything runs fine.
Any combo of buffers/springs works fine with 220s. And 190s. Supressed or not cycles fine either way.
The problem I have is that with 190s no matter the spring/buffer combo my bcg will jam rounds between the feed ramps and mag lips randomly causing brass scarring and bending.
I have polished feed ramps, drilled gas port, tried different mags and bcgs, factory sub-x190s along with remanned and custom sub-x 190s,
and still running into this issue.
I want the 190s to be my main round but due to this issue they cant be trusted and I need help.
I was told to try a 20rd mag because the 30rd may be too slow to present the round but if it feed 220s without issue then 190s should be faster and better.
The system would be severly over gassed with standard supersonics and thats what allows to run with or without the can on subs.
With all that ive tested and done I dont belive its a gas buffer bcg or cycle issue but a feed issue I cant seem to pinpoint. Any ideas would be great.
It was undersized and couldnt cycle 220s with 1.7 oz buffer and yellow spring. Adj gas block can only remove gas and with it orginally already being really undergassed it would have only added to the problem.
I never intended for supers to be used. If i ever want to then yes I need and adj gb. Ive always had the can on it. At first it had to be used as a bolt gun bassically. I did check gb alignment and any obstructions + gas key and for any leaks and tried diffrent bcg before having a local gun smith do the drilling. Id always rather over vs under gasses.
Ok…so the history of 300blk is that it was meant to run subs on an 8.5" barrel with standard gas block, carbine spring, h2 buffer, and a can. I know because i have one and it will shoot anything.
Along came adj gas blocks which help tame supers.
#1 the drilled gas port is a major problem. I suggest you get an adj gas block. Take note that you may see more fouling and or wear due to your change. #2 put the gun back to stock as best as possible and change one thing at a time. Get it working with supers and then go to subs. #3 try regular pmags or lancers. I have never seen a reliable 300blk pmag.
For ammo I settled on ammoinc stealth 220s.
I started with sub-x 190s and those are the problem children.
It cycles runs and feeds s&b 220s, gorilla 205s. Sig 220s, hornady 208s and winchester 220s perfectly after gass port drilling and switching to pmag 300 blk mags
Mil spec, pmag, and torx 5.56 mags gave nothing but issues after loading 10-15 rounds of 300 and caused nothing but failures.
Ive never indended to run supers I got this rifle for both home defense and hog hunting within 150m I have my 7.62x54r for anything further or bigger.
I went through about 2 months of range trips and troubleshooting changing one thing at a time and even trying different lubes and ammos to get this thing running rite with 190s.
I like the ballistics accuracy and expansion of the 190s the best and after all that has been done still cant run them reliably. Any other sub runs perfectly.
Just to clarify I do get lrbl on every single weight including 190s. But I have to run mil spec buffer with yellow spring with the 190s. When shooting the 190s it cycle fine and will cycle several rounds some times up to 10 or 15 before a feeding jams happens and other times only 1 or 2 before it happens.
Ive tried loading the mags in 5 round interavals from 5 to 30 rounds and its never consistant on when a fail to feed will happen. Ive ran full mags with no isse with them then reloaded mag and have it fail to feed every other round. Ive put ligther buffers so light that a full mag would act like the bolt catch because there wasnt enough force to strip the round even using the charging handle and had to use the forward assist to ride the bolt forward. Ive gone heavy enough to cause short stroking using custom buffers from a buddy.
With yellow spring and mil spec buffer everything is perfect and with standard sping and 2.4oz buffer everything is perfect. Every weight except 190s will cycle feed eject and run 0 issues at all. Slow rapid hot or cold. 190s will as well except for failing to strip out of mags and getting marred up.
If you never intended to run supers why mess with the gas port when you have a can? Changing that IMO has you really messed up. My 12 yr old 300 blk will run everything i put in it? Why? Because an engineer far smarter than me did the math and knew the combo of gas port, barrel twist, and mechanics to make it work right.
