I just loaded some 300BLK round using 190gr Hornady Sub-X and 8.1gr of LilGun. They chrono'd at 1184FPS avg, and were not subsonic (the 223's I loaded up that chronod at under 1000fos were silent.... until they hit the backstop). According to the Hodgdon data, 8.3gr should have put it at 1,044fps, so it seems other factors may be at play. They also didn't cycle right - they cycled enough to eject the empty, but the BCG (This is an AR15 BTW) got hung up just shy of being able to strip off the next round -even after the last round, it got hung up part way back. On the other hand, I've shot 300BLK subsonic rounds using 208gr Hornady A-max bullets that cycled perfectly. I have IMR4198 and IMR4227 that I could also try, and I note that apparently 4198 is a compressed load with the 190gr SubX. Is it possible that a different powder might provide different results with regards to cycling? Does anyone have a good load using the 190gr SubX that'll cycle an AR - OR, are there any BCG or buffer spring options that might allow proper cycling with the SubX round (I'm not against a different BCG or buffer spring to make them cycle right)?
Subsonic 300Blk
- Thread starter 357SigFan
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Atavar
Member
You are going to have to make some choices.
Use enough powder to cycle
Or
Reduce powder to keep subsonic
Or
Change the recoil spring
Use enough powder to cycle
Or
Reduce powder to keep subsonic
Or
Change the recoil spring
mcb
Member
Try the 4227, I use it with 220 gr bullets with good luck. Accurate 1680 is another good candidate.
RockRat64
Member
4227 is a good choice. CFE Blk seems to come around often and is similar to 1680.
There is a list of powders out there, maybe on 300blktalk? Guy(s) there list the powders for super and subs that are good at cycling the Ars.
Lennyjoe
Member
I’m using 1680 with 190 Sub X and get great performance with o breaking the sound barrier.
I would try the 4227. Generally if it takes more grains of powder it to get the same velocity. It will have more gas also. I've found this in tuning my AGB in my 5.56.
Lil gun is all I've used in 300 BO and it was a contender. So I didn't have issues with cycling.
berettaprofessor
Member
I use 10.1 grains of IMR4227 behind a Hornady 208 grain bullet...it cycles my 300BO carbine length system...chronies at 1017fps.
Thanks for the input. I loaded up five with 10.3gr of IMR4227 and five with 11.3 gr of IMR4198. The 4227 acted the same as the 8.1gr of LilGun, cycling enough to eject the empty but not enough to grab the next round and getting stuck mid-stroke. The 4198 load cycled the gun properly, but both loads were cooking along at around 1240fps average (and this is out of a 16" barrel), so I think the next thing to try is a string loaded with 11.1gr of IMR4198. I'll probably also see if I can find a can of Trail Boss and Accurate 1680 to work with as well. If I get a charge that runs reliably in the 1050-1100fps range but doesn't cycle the gun (and can't find one that does both), I'm not against trying a different spring. The IMR4198 loads also seemed to be quite accurate - I was only shooting at 25yds, but I was shooting with an Eotech and not really trying that hard since I was mainly gathering velocity data, and I can cover the five shot group with a penny.
mcb
Member
OP what length gas system? The shorter the better with Subs.
There's your problem right there. You need a pistol length gas system to reliably run subsonic. I went through issues very similar to yours on 2 ARs. Both had carbine length barrels initially. They now have pistol length systems and they simply run.
Hmmm.. ok, well, let's see where I can get with powders first - There's an obvious difference in how it runs with different powders. The 4198 loads cycled fine but were running too fast (roughly the same speed as the 4227 and a hair faster than the LilGun), and I know 208gr subs loaded with Accurate 1680 run fine in it, so there may be a solution that doesn't involve a new barrel and gas tube. Considering I know 208gr subs loaded with 1680 work well, and the load data, according to Hornady, fo rhe 208gr and 190gr and 1680 are very similar, that may end up being the solution if I can find the powder - but we'll see.
mcb
Member
You might try switching to a heavier bullet. That might help you find a subsonic loads that runs in your carbine had system.
25-20 WCF
Member
I don’t remember anyone recommending a new barrel or gas tube. What was recommended was a new buffer spring, a cheap part which requires just a few minutes to change. I don’t understand why the OP continues trying different powders with dubious results (wasting hard-to-find components) unless he wants to run both sub and sonic loads without changing the spring. But won’t a pistol spring work with both types of loads?
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mcb
Member
I doubt a lighter buffer spring will make much difference. And if you go too light you run into other issues on the forward stroke. A lighter buffer, if the OP is running a heavier than standard, might help a little.
If it's going to be a dedicated subsonic gun you could always open up the gas port. A carbine length gas system with a port for supersonic ammo is going to struggle to get enough gas in the system to work with subsonic loads.
If it's going to be a dedicated subsonic gun you could always open up the gas port. A carbine length gas system with a port for supersonic ammo is going to struggle to get enough gas in the system to work with subsonic loads.
243winxb
Member
Is a suppressor installed?
Actually I said that I changed my barrels. The problem with trying to run subsonic in a carbine length tube is the lack of gas, as mentioned by @mcb.
IMO, unless you are running a dedicated supersonic gun, the only way to set up a Blackout is with the pistol length gas system.
So far, I've only tried loads using powder that I have on hand, and I have a LOT of 4198 in sealed containers, and this is the first application I've found to potentially use it. I don't know what my grandfather loaded with it, but he had a lot. So far I've only used about 56gr (or less, depending on the powder) of each powder, and one pound of powder can load over 600 of these - not really a travesty. If I get a load with 4198 (which right now seems the most promising) that'll run slow enough and still cycle right, that's even cheaper than a spring, as I already have the components. Besides, I wouldn't consider going to the range for some trigger time a waste
.Yes.
Lennyjoe
Member
If you were in the neighborhood of Dayton Ohio I’d sell ya a pound of 1680
n2omike
Member
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A .223 loaded subsonic is basically a .22lr... about the same weight bullet and velocity. .22lr is quiet as a mouse fart through a can. 9mm is also really quiet... not as quiet as the .22lr, but works good with a can. 300BO is not as quiet as the 9mm, and quite a bit louder than the .22lr.
As for function, if you have a pistol gas system, about any powder will work. A PSA pistol upper will function all the way down to less than 800fps with a 220 grain bullet. Carbine and rifle gas systems need a lot more gas, as the port is further toward the muzzle.
In regards to powders, H110 doesn't produce consistent velocities until it's loaded hot enough for supersonic velocities... at least in a 10.5" barrel. That powder does not like low pressures.
Powders that are designed to produce a lot of gas for gas operated AR15 style rifles (1680, etc) will be louder. Lil Gun is excellent, as is 4227 and Enforcer can produce good results. 2400 can also work well with a pistol gas system. All powders cycle better when used with a can. The faster the powder, the more completely it will be burned within the barrel, and the quieter it should be.
Good Luck
As for function, if you have a pistol gas system, about any powder will work. A PSA pistol upper will function all the way down to less than 800fps with a 220 grain bullet. Carbine and rifle gas systems need a lot more gas, as the port is further toward the muzzle.
In regards to powders, H110 doesn't produce consistent velocities until it's loaded hot enough for supersonic velocities... at least in a 10.5" barrel. That powder does not like low pressures.
Powders that are designed to produce a lot of gas for gas operated AR15 style rifles (1680, etc) will be louder. Lil Gun is excellent, as is 4227 and Enforcer can produce good results. 2400 can also work well with a pistol gas system. All powders cycle better when used with a can. The faster the powder, the more completely it will be burned within the barrel, and the quieter it should be.
Good Luck
Lennyjoe
Member
Funny thing for me is I tried LilGun and ended up liking 1680 better for both my 190 Sub-X and 208 gr Hornady loads
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